Aggression before Versailles

The European Journal of International Law Vol. 29 no. 3

EJIL (2018), Vol. 29 No. 3, 773–808 doi:10.1093/ejil/chy038

RandallLesaffer*

Abstract

The roots of aggression as a concept of international law are rarely traced back beyond the end

of World War I.The Versailles Peace Treaty of 28 June 1919 and the Covenant of the League

of Nations, which constituted its rst 26 articles, are often quoted as the rst seminal steps

towards its emergence as a key concept of the modern jus contra bellum. In this article, this

assumption is tested and read against the backdrop of 18th- and 19th-century use of force

law. The paper makes three claims. First, although international use of force law underwent

important change during the 19th century, it remained deeply rooted in the jus ad bellum

of the early modern age, which in turn had its roots in late-medieval scholarship. Therefore,

19th-century doctrine and state practice cannot be fully appreciated without an awareness of

the historical tradition they built on. Second, although it cannot be denied that 19th-century

international law conceded to states the right to resort to force and war, this right was condi-

tional and restricted. Third, both early modern as well as 19th-century international lawyers

referred to a concept of aggravated violation of jus ad bellum which – at least in theory – trig-

gered reaction and even sanction by the international society of states against the perpetrator.

This was, from the 18th century onwards, loosely and inconsequentially, but with increasing

frequency, referred to as ‘aggression’ or ‘aggressive war’, both in diplomatic practice as well as

in legal scholarship. Although the Versailles Peace Treaty broke with existing peace-making

practice and returned to a discriminatory conception of war by blaming the war on Germany

and its allies and by sanctioning them, it drew on a pre-existing conception of aggression as

a violation of use of force law.

1 Introduction

The roots of aggression as a concept of international law are rarely traced back

beyond the end of World War I.The Versailles Peace Treaty of 28 June 1919, and the

Covenant of the League of Nations that formed its rst 26 articles, are often quoted as

* Professor of Legal History, Tilburg University, The Netherlands; Professor of International and European

Legal History, University of Leuven, Belgium. E-mail: lesaffer@tilburguniversity.edu.

774 EJIL 29 (2018), 773–808

the rst seminal steps towards its emergence as a key concept of the modern jus contra

bellum.

Article 10 of the Covenant named ‘external aggression’ the concern of all

members of the League of Nations and made it a central plank of its system of collec-

tive security.

Aggression gured prominently in the actual peace settlement between

the Allied and Associated Powers and Germany. Article 231 stipulated the liability

of Germany for all of the loss and damages of the Allied powers and their nationals

‘as a consequence of the war imposed upon them by the aggression of Germany and

her allies’.

Article 227 provided for the prosecution of the former German Emperor

Wilhelm II (1859–1941) for ‘a supreme offence against international morality and

the sanctity of treaties’. The article did not expressly mention aggression, but the his-

tory of its origins makes clear that the former emperor was to be arraigned for, among

others, the premeditation and execution of a war of aggression. This article is gener-

ally considered the historic precursor for the prosecution of crimes against peace after

World WarII.

Careful students of the concept’s history have quoted the condemnation of the

French Emperor Napoleon I(1769–1821) by the Congress of Vienna after his nal

defeat and his subsequent imprisonment as a precedent for Emperor Wilhelm II’s

arraignment or have pointed to the use of the term aggression in 19th-century alli-

ance treaties and justications for war. But none have given this more than a cursory

mention. These references to aggression in the practice of the 19th century have been

generally dismissed as part of a political or moral discourse that fall outside the ambit

of international law.

They stand at odds with the prevalent view that the 19th-cen-

tury jus ad bellum was almost literally just that – the mere recognition that sovereign

states had a right to resort to force and war, leaving no room for aggression as a vio-

lation ofit.

Versailles Peace Treaty 1919, 225 Parry 188. Brownlie, ‘The Use of Force in Self-Defence’, 37 British

Yearbook of International Law (BYIL) (1961) 183, at 222; A.Cassese, International Criminal Law (2003), at

111; Grifths, ‘International Law, the Crime of Aggression and the Ius ad Bellum’, 2 International Criminal

Law Review (2002) 301, at 303–304; Eagleton, ‘The Attempt to Dene Aggression’, 264 International

Conciliation (1930) 581, at 586–588; Murphy, ‘The Crime of Aggression at the International Criminal

Court’, in M.Weller (ed.), The Oxford Handbook of the Use of Force in International Law (2015) 533, at

534–535; O’Connell and Niyazmatov, ‘What Is Aggression? Comparing the Jus ad Bellum and the ICC

Statute’, 10 Journal of International Criminal Justice (JICJ) (2012) 189, at 189–190; Sellars, ‘Delegitimizing

Aggression: First Steps and False Starts after the First World War’, 10 JICJ (2012) 7, at 7–18; J.Stone,

Aggression and World Order: ACritique of the United Nations Theories of Aggression (1958), at 10.

Covenant of the League of Nations 1919, 13 AJIL Supp.128 (1919).

The other peace treaties that were concluded at the peace conference of Paris with Germany’s former

allies included similar clauses. Treaty of Saint-German-en-Laye with Austria 1919, 226 CTS 8, Art.

177; Treaty of Neuilly-sur-Seine with Bulgaria 1919, 226 CTS 332, Art. 121; Treaty of Trianon with

Hungary 1920, Art. 161, reprinted in K.Strupp (ed.), Documents pour servir à l’histoire du droit des gens

(2nd edn, 1923), vol. 5, at 44; Treaty of Sèvres with Turkey 1920, Art. 231, reprinted in ibid., vol. 5, at

62.

Baldwin, ‘The Proposed Trial of the Former Emperor’, 29 Yale Law Journal (1919–1920) 75, at 79;

I.Brownlie, International Law and the Use of Force by States (1963), at 351–352; C.A. Pompe, Aggressive

War: An International Crime (1953), at 47–53.

Aggression before Versailles 775

The reading of the Versailles Peace Treaty as the rst step in the criminalization

of aggression falls squarely in line with the dominant historical narrative of interna-

tional use of force law. This contrasts the gradual, but steady, emergence of the jus

contra bellum between 1919 and 1945 with the almost complete absence of any legal

restrictions on the resort to force and war at the turn of the 20th century. Under this

view, the decades straddling the year 1900 saw the nal demise of the just war doc-

trine, the decline of which had started with the rise of the sovereign state in the early

modern age (circa 1500 to circa 1800). They marked the nadir of the role of interna-

tional law in constraining war. Versailles and the League of Nations made an end to

this lawlessness by introducing a new regime of use of force under international law.

Some authors have labelled this a return to the just war doctrine.

In the past, a few international lawyers have reached the uneasy conclusion that

19th-century doctrine and practice of use of force were altogether more complicated

and sophisticated than they were generally credited for.

But only in recent years did

scholars challenge the prevalent narrative head on. Over the past decade, historians

have indicated that the just war doctrine has proven far more resilient in the legal writ-

ings and state practice of the early modern age than was traditionally acknowledged.

In his seminal historical study of war as a legal concept, Stephen Neff argues that,

while the just war lost its relevance for the legitimization and restriction of actual war

during the 19th century, it formed the intellectual foundation under different catego-

ries of measures short of war, such as self-defence, actions of necessity and, above

all, reprisal.

Agatha Verdebout estimates that the view that international law was

indifferent to the legality of force and war was, contrary to what most post-World

War I international lawyers assumed, not representative of 19th-century doctrine

or practice. She lists only four ‘radical positivists’ from the late 19th or early 20th

centuries who defended the indifference thesis: John Westlake (1828–1913), Thomas

J. Lawrence (1849–1920), Lassa Oppenheim (1858–1919) and Dionisio Anzilotti

(1869–1950). In her opinion, it tted the political agenda of the League of Nations

Brownlie, supra note 4, at 19–65; Y.Dinstein, War, Aggression and Self-Defence (5th edn, 2012), at 75–79;

T.M. Franck, Recourse to Force: State Action against Threats and Armed Attacks (2002), at 9–10; Nussbaum,

‘Just War – a Legal Concept’, 42 Michigan Law Review (1943–1944) 453; O’Connell, ‘Peace and War’, in

B.Fassbender and A.Peters (eds), The Oxford Handbook of the History of International Law (2012) 272;

T.Ruys, Armed Attack and Article 51 of the UN Charter: Evolutions in Customary Law and Practice (2010), at

53–54; M.N. Shaw, International Law (7th edn, 2014), at 811–814; Von Elbe, ‘The Evolution of the Just

War Doctrine in International Law’, 33 American Journal of International Law (AJIL) (1939) 665.

S.C. Neff, War and the Law of Nations: AGeneral History (2005), at 279–90; Von Elbe, supra note 5, at

687–8.

Brownlie, supra note 4, at 46–50; J. Gardam, Necessity, Proportionality and the Use of Force by States

(2004), at 39–40.

B. Klesmann, Bellum Solemne: Formen und Funktionen europäischer Kriegserklärungen des 17. Jahrhunderts

(2007); Lesaffer, ‘Defensive Warfare, Prevention and Hegemony: The Justications for the Franco-

Spanish War of 1635’, 8 Journal of the History of International Law (JHIL) (2006) 91 and 141; A.Tischer,

Ofzielle Kriegsbegründungen in der Frühen Neuzeit: Herrscherkommunikation in Europa zwischen Souveränität

und korporativem Selbstverständnis (2012).

Neff, supra note 6, at 215–249.

776 EJIL 29 (2018), 773–808

period, which rendered a central place to international law in securing peace, to dis-

miss the role of international law in the pre-war period because it had failed.

In her

study of the role of international law during World War I, Isabel Hull contends that,

in spite of the dominant view, international law did play a signicant role in decision-

making, diplomacy and propaganda at the commencement of the war. She points a

nger at the concerted action of the German Foreign Ministry, German diplomats and

German academicians during and after the Parisian Peace Conference to discredit the

Versailles Peace Treaty and its war guilt clause.

The success of these actions, which

were also evident within international academia, goes indeed some way towards

explaining why post-World War Iinternational lawyers chose to believe that interna-

tional law did not restrict the right of states to resort to force or war in the years before

1914.

This article subscribes to this recent turn in the historic narrative of international

use of force law. It makes three claims. First, although international use of force law

underwent important change during the 19th century, it remained deeply rooted in

the jus ad bellum of the early modern age, which in turn had its roots in late medie-

val scholarship. Therefore, 19th-century doctrine and state practice cannot be fully

appreciated without an awareness of the historical tradition on which they are built.

Second, although it cannot be denied that 19th-century international law conceded

to states the right to resort to force and war, this right was conditional and restricted.

Third, both early modern as well as 19th-century international lawyers referred to a

concept of aggravated violation of jus ad bellum, which – at least in theory – triggered

reaction and even sanction by the international society of states against the perpetra-

tor. From the 18th century onwards, this was loosely and inconsequentially, but with

increasing frequency, referred to as ‘aggression’ or ‘aggressive war’ both in diplomatic

practice as well as in legal scholarship. Although the Peace of Versailles broke with

existing peace-making practice and returned to a discriminatory conception of war

by blaming the war on Germany and its allies and by sanctioning them, it drew on a

pre-existing conception of aggression as a violation of use of forcelaw.

The article falls into four substantial sections. Section 2 explores the place of aggres-

sion in the jus ad bellum of the 17th and 18th centuries. The focus is on the work

of Emer de Vattel (1714–1767), who was the most inuential of the early modern

Verdebout, ‘The Contemporary Discourse on the Use of Force in the Nineteenth Century: ADiachronic

and Critical Analysis’, 1 Journal of the Use of Force and International Law (JUFIL) (2014) 223, with the

thoughtful reection by Ruys, ‘Editorial Comment: From Passé Simple to Futur Imparfait? AResponse to

Verdebout’, 2 JUFIL (2015)3.

I.V. Hull, A Scrap of Paper: Breaking and Making International Law during the Great War (2014), at 1–15.

Dickmann, ‘Die Kriegsschuldfrage auf der Friedenskonferenz von Paris 1919’, 197 Historische Zeitschrift

(1963) 1, at 59–94; Evans and Baylen, ‘History as Propaganda: The German Foreign Ministry and the

Enlightenment of American Historians on the War-Guilt Question, 1930–1933’, in K. Wilson (ed.),

Forging Collective Memory: Government and International Law through Two World Wars (1996) 151; Herwig,

‘Clio Deceived: Patriotic Self-Censorship in Germany after the Great War’, in Wilson, ibid., 87; P.Krüger,

Deutschland und die Reparationen 1918/1919: Die Genesis der Reparationsproblems in Deutschland zwischen

Waffenstilstand und Versailler Friedensschluss (1973), at 82–92; see also Ofcial German Documents Relating

to the World War, 2 vols (1923).

Aggression before Versailles 777

writers of the law of nature and of nations during the 19th century and who was

most elaborate on the subject. Section 3 illustrates the place of aggression in the early

modern jus ad bellum with an example from 18th-century state practice – namely,

the case of the attack on Saxony and the Habsburg monarchy by King Frederick II

of Prussia (1712–1786) in the summer of 1756. Section 4 briey explains the major

evolutions of the jus ad bellum in the century before 1914, arguing for the resilience

of much of early modern tradition. Finally, section 5 turns to the Peace Conference of

Paris in 1919.

2 Just and Legal War in Early ModernEurope

The jus ad bellum of the 17th and 18th centuries operated two different, but inter-

connected, conceptions of war: just war and legal war. The doctrine of just war had

reached its classical articulation in the writings of canonists and theologians from

the 12th and 13th centuries. The concept of legal war was a product of the civilian

jurisprudence of the 12th–15th centuries. In his De Jure Belli ac Pacis, Hugo Grotius

(1583–1645) recycled both concepts and gave them a place within his dualist sys-

tematization of the law of nations.

Whereas just war pertained to the natural law

of nations, which applied in conscience (in foro interno), legal war, or bellum solemne

as he labelled it, pertained to the positive law of nations, which applied to the external

relations between states (in foro externo).

After Grotius, this dualism of operating two

different sets of norms with relation to war – one at the level of natural justice and one

at the level of its effect under the positive law of nations – became mainstream and

remained so until the 19th century.

A just war is an action of forcible self-help in order to seek redress for the viola-

tion of a right. In his classical rendering, the theologian Saint Thomas Aquinas (circa

1225–1274) listed three conditions for a war to be just: authority, just cause and righ-

teous intention.

Authority signies the absence of a higher authority. Later authors

would sometimes list different just causes. Grotius distinguished between self-defence,

redress and punishment. But, in each case, the underlying cause was an injury com-

mitted by the enemy, including an unjustied armed attack.

Righteous intention

referred to the mental disposition with which a belligerent entered and fought a war.

In practical terms, it referred to the war’s purpose, which should be the attainment

H. Grotius, De Jure Belli ac Pacis Libri Tres (1925 [1625]).

Ibid., at 1.3.4.1, 3.3.4–5, 3.3.12–13.

S.C. Neff, Justice among Nations: AHistory of International Law (2014), at 143–213. For examples of this

dualism, see C.van Bynkershoek, Quaestionum Juris Publici Libri Duo (1930 [1737]), at 1.1–2; G.F.von

Martens, Précis du droit des gens de l’Europe (2nd edn, 1804), at 8.2.265–267; S.Rachel, De Jure Naturae

et Gentium Disserationes (1916 [1676]), at 2.39–46; J.W. Textor, Synopsis Juris Gentium (1916 [1680]),

at 16.8–12, 17, 18.1–4; R.Zouche, Iuris et Iudicii Fecialis, sive, Iuris Inter Gentes (1911 [1650]), at 1.6,

2.6.1–2. The distinction between just and formal war is also debated by theradical naturalist Samuel

Pufendorf (1632–1694), De Jure Naturae et Gentium Libri Octo (1934 [1688]), at 8.6.1–5,9.

T. Aquinas, Summa Theologiae IIaIIae 40.1.

Grotius, supra note 13, at 2.1.2.

778 EJIL 29 (2018), 773–808

of a just peace. To these three conditions, one can add two more that were inherent

in the logic of late medieval just war doctrine: necessity and proportionality. In early

modern doctrine, the former was increasingly translated into an obligation to exhaust

all peaceful means to obtain redress before resorting towar.

In principle, a just war opposes a just to an unjust belligerent. It discriminates

between the belligerent sides, both during war and at the time of peace making.

Aconsequential application of the just war doctrine denies the benets of the laws of

war, such as the right to conquer, take booty or exact ransom to the unjust belliger-

ent, as he holds no right to wage war in the rst place. At the end of a just war comes

a just peace, whereby the just belligerent receives recognition of the contested right

and is granted reparation for all of the damages and costs pursuant to the injury and

the war.

A legal war is a form of dispute settlement. For a war to be legal, it sufces that

it is waged between sovereigns and, according to most early modern writers, is for-

mally declared.

The state of war triggers the equal application of the laws of war to

all belligerents. The outcome of the war, or of the ensuing peace negotiations, deter-

mines the attribution of the right under dispute and creates title to it. Alberico Gentili

(1552–1608) famously likened a legal war to a civil trial.

Similar to a civil trial, both

sides have the right to defend their claims. Whereas in a civil trial the judge is supposed

to render justice, force decides the outcome in war.

Modern scholars have readily dismissed the resilience of just war in the early mod-

ern literature of the law of nature and of nations as empty lip service to an old, vener-

ated tradition. Taking a cue from John Austin (1790–1859), they generally disparage

just war as a moral, rather than a legal, category.

But this constitutes a far too bleak

view, which vastly underestimates the normative force of natural law in general and

the just war doctrine in particular. This modern view is inspired by a too secular,

anachronistic reading of early modern natural law.

Under the pens of mainstream

writers of the law of nature and of nations of the early modern age, natural law was

only secularized in the most limited of manners. Most writers, such as Grotius, did not

take the untying of natural law from Christian religion any further than the acknowl-

edgement that people could understand natural law regardless of their faith.

This

concession served to bridge the gap between Christians of different denominations in

Europe after the Reformation and to indicate a common basis for legal relations with

P. Haggenmacher, Grotius et la doctrine de la guerre juste (1983), at 51–444; Neff, supra note 6, at 45–82;

F.H. Russell, The Just War in the Middle Ages (1975).

B.de Ayala, De Jure et Ofciis Bellicis et Disciplina Militaris (1944 [1584]), at 1.2.34; A.Gentili, De Jure Belli

Libri Tres (1598, edn 1612, Classics of International Law, 1933), at 1.2, 1.6; Grotius, supra note 13, at

1.3.4.1.

Gentili, supra note 19, at 1.2.18, 1.6.47–52.

J.Q. Whitman, The Verdict of Battle: The Law of Victory and the Making of Modern War (2012), at 25–132.

J. Austin, The Province of Jurisprudence Determined, edited by W.E. Rumble (1995 [1832]), at 19–21.

Silverstrini, ‘Justice, War and Inequality: The Unjust Aggressor and the Enemy of the Human Race in

Vattel’s Theory of the Law of Nations’, 31 Grotiana N.S. (2010) 44, at 47–58.

Grotius, supra note 13, Prolegomena 11.

Aggression before Versailles 779

peoples outside Christian Europe, such as the American Indians. But, to most classical

writers of the law of nature and of nations, the ultimate foundation of natural law

lay with God. More importantly, the application of natural law in conscience tied it

back to religion and moral theology. For most of these writers, whatever their appurte-

nance in terms of Christian denomination, a violation of natural law equalled sin and

could lead to the condemnation of the soul at the end of times. Whereas to the mod-

ern lawyer, a natural obligation is an unenforceable obligation, in the minds of most

scholars, statesmen and diplomats of early modern Europe, precepts of natural law

were enforceable. They would be enforced by the most supreme judge of all.

It was no

coincidence that Grotius, his contemporaries and his followers recycled several doc-

trines from late medieval canon law and theology, such as just war, into natural law.

Just and legal war shared an important similarity to the extent that both turned

on a conict about rights. But, whereas just war was founded on the assumption that

only one side was in the right, legal war lifted this assumption. Just war was an instru-

ment for the enforcement of a pre-existing right, while legal war was an instrument to

settle a disputed right. To build on the metaphor of Gentili, if legal war could be likened

to a civil trial, just war was tantamount to the bailiff knocking on the door to enforce a

prior verdict. The problem with just war was that, among sovereigns, it was generally

impossible, with God being silent and without a common, human authority to judge,

to establish this verdict with certainty. Herein lay the ontological connection between

just and legal war, a connection that is generally disregarded by modern legal scholar-

ship because of its association to the theological foundations of justwar.

The late medieval canonists and theologians who rst gave the just war doctrine its

classical form were primarily concerned with the question of the impact of war on an

individual’s soul and afterlife. To them, the justice of war was indeed a matter of con-

science.

In this respect, they had few qualms about the unpractical consequences of

discriminating between just and unjust belligerents for the application of the rights

of war or about the lack of realism in the proposition that belligerents should render

justice after war, regardless of its outcome. The impracticality of these consequences,

chiey among them the lifting of the reciprocity in the application of the laws and cus-

toms of war, however, greatly troubled the civilian jurists of the late middle ages and

the Renaissance who adopted the just war doctrine. They were primarily concerned

with the effects of the law in the relations between princes and states in the here and

now. It was for this reason that they devised the concept of legal war.

Ibid., Prolegomena 12, 20; E.de Vattel, Le droit des gens ou principes de la loi naturelle (1916 [1758]), at

3.8.137; J.Gordley, The Jurists: ACritical History (2016), at 66–81.

Lesaffer, ‘Roman Law and the Intellectual History of International Law’, in A.Orford and F.Hoffmann,

The Oxford Handbook of the Theory of International Law (2016) 38, at 51–57; Silvestrini, supra note 23, at

56–58.

See the title of the section in Aquinas, which listed the three conditions for just war: ‘Whether it is always

a sin to wage war.’ Aquinas, supra note 16, IIaIIae 40.1; translation in R.W. Dyson (ed.), Aquinas: Political

Writings (2002), at 240.

Greenwood, ‘War and Sovereignty in Medieval Roman Law’, 32 Law and History Review (2014) 31.

780 EJIL 29 (2018), 773–808

The standard reasoning that connected legal war to just war held that in the light

of the impossibility to establish among sovereigns who had right on his side, both sides

as well as third parties in the external forum had to act as if both sides had just cause.

By consequence, all belligerents were supposed to have a right to wage war. Under the

conception of legal war, the discrimination between the just and the unjust belligerent

was lifted since the judgment of the underlying claims was suspended until the nal

judgment. This explanation for legal war as a default solution to the riddle of justice

in war was repeated by numerous writers from the 15th to the early 20th centuries.

Its oldest explicit articulation known comes from Raphael Fulgosius (1367–1427).

Vattel’s clear restatement of it was crucial for its survival in 19th-century literature.

There were actually three, rather than two, conditions for a war to be legal. Each

belligerent needed to forward a plausible just cause. In case a belligerent did not make

such a claim, or in case the claim was manifestly unjust, the uncertainty about the jus-

tice of each side’s cause was lifted, and the suspension of judgment became unneces-

sary. By consequence, the just war re-entered the world of men in full force and caused

legal effects in the secular world. Here, a space opened to conceive of a violation of the

jus ad bellum, which led to a duty to compensate all of the costs and damages of the

war to the just belligerent. It was in this space that the concept of aggression emerged.

None of the classical jurisprudents of the law of nature and of nations of the ancien

régime explored this space more elaborately than Vattel. The Swiss diplomat reiterated

the dual system of just and legal war (la guerre en forme).

He insisted that a war could

only be considered legal inasmuch as the justice of the different belligerents’ claims

remained uncertain. Thereto, all belligerents needed to forward a just cause, even if this

was mere pretext. Vattel acknowledged that princes and rulers were often far from sin-

cere in the justications for war they proffered, but as long as they indicated a just cause,

it was impossible to judge. Failure to forward a just cause, however, lifted the protection

of legality from a belligerent and threw him back into the realm of just war.

Awar that

was manifestly unjust was also illegal. This implied that the unjust side would not benet

from the laws of war and that, at the end of the war, the unjust belligerent would be held

accountable for all of the costs and damages of the just belligerent pursuant to the war.

Although Vattel was particularly elaborate, thus far he did nothing but expound

the logic of the dual system of just and legal war. However, Vattel took the theory

some steps further by adding a moral dimension and attaching severe consequences

to the concept of a manifestly unjust war. Failure to forward a just cause did not only

lay the perpetrator bare to the full consequences of ghting an unjust war, but it also

made the war a concern of the international society of states as a whole. It made

the unjust belligerent into an enemy of mankind.

According to Vattel, neglecting

R. Fulgosius, In Pandectas (1534), ad D.1.1.5.

Vattel, supra note 25, at 3.3.40, 3.12.188; see also C.Wolff, Jus Gentium Methodo Scientica Pertractatum

(1934 [1749]), at 7.889.

Vattel, supra note 25, at 3.3.24–28, 40.

Ibid., at 2.18.335, 3.3.30–33, 3.4.67–68.

Ibid., at 3.4.68, 4.2.18; Silvestrini, supra note 23, at 61–63.

Vattel, supra note 25, at 3.3.34.

Aggression before Versailles 781

to justify war signied contempt for justice and was tantamount to declaring ‘open

war upon all what [was] sacred in human society’. At least, a sovereign who offered a

pretext ‘tacitly [confessed] that agrant injustice merits the indignation of all men’.

Such behaviour warranted two reactions by the society of states. First, all other states

obtained the right to join forces against the enemy of mankind and subdue him. This

also included the right to take measures to guarantee against new transgressions

and safeguard peace and security for the future.

Second, Vattel even suggested that

the sovereign prince of the involved state could be personally punished. However, he

did not insist on this point.

As Walter Rech indicates, Vattel’s concept of common

sanction was not driven by moral indignation and a desire to punish but, rather, by a

concern for collective security.

Although Vattel reiterated the core elements of the

classical just war doctrine, he reframed it by insisting on the fundamental right of self-

preservation as its ultimate basis. Thereby, he placed state security at the heart of his

jus ad bellum. This widened the scope of the concept of just cause to include threats to a

state’s security, thus allowing actions to prevent injury or an anticipated attack. Vattel

thus extended self-defence to anticipatory self-defence.

The category of enemy of mankind was not limited to those failing to offer a just

cause for war. It contained all those whose actions made their use of force manifestly

unjust. Vattel did not list them in any systematic way, but from various remarks, one

can infer three more categories. First, there were the notorious warmongers. Those

were rulers and peoples whose propensity to commit injustice and resort to violence

was so notorious that any justications for war they might proffer were discred-

ited.

Second, there were those rulers who desired to dominate Europe and thereby

threatened to overthrow the balance of power and the security of all states.

Third,

the contempt of a ruler for the sanctity of treaties could stain him as an enemy of

mankind.

Apart from these categories stood ‘barbarian nations’ who fought wars

in uncivilized ways, without regard for the laws and customs of war. This group

was different as it concerned peoples outside Europe, whereas the former categories

all referred to European rulers and peoples. While Vattel was mild with regard to

the punishment for warmongers, disturbers of the balance of power and violators

of treaties, he insisted that these barbarians merited harsh, effective and collective

punishment.

Of all the great writers of the law of nature and of nations of the 17th and 18th

centuries, Vattel was the most explicit and elaborate on the consequences of waging

Ibid., at 3.3.32.

Ibid., at 2.5.70.

Ibid., at 3.4.68, 3.11.184, 4.2.6.

W. Rech, Enemies of Mankind: Vattel’s Theory of Collective Security (2013), at 125–127, 149–157.

Vattel, supra note 25, at 2.4.49, 3.4.42–44.

Ibid., at 2.5.70, 3.3.33–34

Ibid., at 3.3.45–49.

Ibid., at 2.15.222; see Rech, supra note 38, at 182–192.

Rech supra note 38, at 112–127.

782 EJIL 29 (2018), 773–808

a manifestly unjust war.

But he was only partially original. He mainly exploited the

traditional logic of dualism and the interconnection between just and legal war. To

this, he added a concern for collective security, which came from founding the whole

jus ad bellum on the right of self-preservation. This latter move made a lasting imprint

on mainstream doctrine.

The resilience of just war in early modern legal scholarship reected its relevance

for state practice at the time. All through the early modern age, the princes and gov-

ernments of Europe took great trouble in justifying war. For this purpose, they gener-

ally used the discourse of just war. Justications for war were commonly to be found

in formal declarations of war and ofcial manifestos, which were given a wide dis-

tribution within and without the country. These justications served four purposes

and were targeted at four audiences. First, they were meant to assuage the conscience

of the rulers themselves. Second, they were a means of propaganda to shore up the

morale of a belligerent’s own soldiers and populations and, third, to undercut the con-

dence of the enemy. Here, the religious dimension of just war played a prominent

role. Many thought that God might not only rule on the justice of war at the end of

times but also might already indicate his favour in war. While this was a widely spread

popular belief, it was also shared by some theologians and legal scholars.

Fourth,

the justications were addressed to the governments of allies and neutral states. The

former target audience was of particular importance as most alliance treaties were

defensive and only triggered the casus foederis in case of an unprovoked attack by the

enemy – in other words, when the ally could indicate to be the just belligerent.

By the second half of the 17th century, a standard line of justication had devel-

oped in declarations and manifestos of war. Usually, belligerents forwarded four argu-

ments for their decision to resort to war. First, they opposed the desire of the enemy to

do harm to their own desire for peace. Second, this was proven by citing a preferably

extensive list of transgressions of one’s rights over a long period of time. This consti-

tuted just cause but, third, also showed that one had done everything to avoid war and

that it was the enemy’s behaviour that made the war an appropriate, proportional

and necessary reaction. Lastly, there was a clear preference to argue defensive war, in

the sense that the enemy used force rst, regardless of how small this force might be.

In the rare case that the last claim was not made, governments were at least implicitly

conceding they were starting an offensive war.

In these cases, the insistence that the

war was just and that the belligerent could not be considered guilty of an unjustied

attack was only greater. As princes knew, being labelled an aggressor could carry its

Wolff, supra note 30, at 6.626–636, 652, 965–969; Rech, supra note 38, at 155–157. Gentili expressly

denied that a manifestly unjust war lifted the protection of its legality from the unjust side, as, so he

claimed, ‘laws are not based upon rare instances and adapted to them’. Gentili, supra note 19, 1.6.51–52.

Grotius, supra note 13, Prolegomena 20; J.Cornette, Le roi de guerre: Essai sur le souveraineté dans la France

du Grand Siècle (1993), at 155–165.

In classical doctrine, whether a war is defensive or offensive depends on who uses force rst. Both types of

war can be just or unjust. Adefensive war is only just if it counters an unjust attack; an offensive war is

just when it is waged to redress injury. Wolff, supra note 30, at 6.615; Vattel, supra note 25, at 3.3.28.

Aggression before Versailles 783

consequences. Few had as much reason to fear this as King Frederick II of Prussia

when he launched the Third Silesian War.

3 A Case of Aggression: The Third SilesianWar

On 29 August 1756, the Prussian army invaded Saxony. After having secured the

electorate, the invading army launched its attack on Bohemia, which formed part of

the Austrian-Habsburg conglomerate. The same day, 13 September, King Frederick

II formally declared war on the Empress Maria Theresia (1717–1780), ruler of the

Austrian monarchy.

At the time of his attack, Frederick II already held a reputation

as a recidivist transgressor of the law of nations. The late summer invasion of that

year was not the rst offensive war he had started. It was the third, after his invasion of

Silesia in 1740, which was then a possession of the Habsburg dynasty, and his attack

on Saxony and Bohemia in 1744. To this, his detractors could add the series of viola-

tions of treaty obligations he had committed – in particular, his triple betrayal of his

French ally during the war of the Austrian succession (1740–1748). Frederick’s bad

reputation as an opportune expansionist would make a lasting imprint on history. In

the 20th century, it further suffered from his close association with Prussian militar-

ism, which was indicated by Germany’s enemies and many historians as one of the

major causes for the conagrations of 1914 and 1939.

Most of all, it was King Frederick II’s opportunist conquest of Silesia in 1740,

shortly after the death of Emperor Charles VI (1685–1740) and at the time of the

strenuous succession by his daughter Maria Theresia, which vested Frederick II’s black

For numerous examples of early modern declarations and manifestos of war that used this standardized

just war discourse, see Klesmann, supra note 8; Tischer, supra note 8.Furthermore F.J. Baumgartner,

Declaring War in Early Modern Europe (2011); Lesaffer, ‘Too Much History: From War as Sanction to the

Sanctioning of War’, in Weller, supra note 1, 35, at 42–45. For detailed analyses of some particular

wars, see Lesaffer, supra note 8; Lesaffer, ‘Between Faith and Empire: The Justication of the Spanish

Intervention in the French Wars of Religion in the 1590s’, in M.Koskenniemi, W.Rech and M.Jiménez

Fonseca (eds), International Law and Empire: Historical Explorations (2017) 101; Piirimäe, ‘Just War in

Theory and Practice: The Legitimation of Swedish Intervention in the Thirty Years War’, 45 The Historical

Journal (HJ) (2002) 499. Representative examples from after 1648, from S.Whatley (ed.), A General

Collection of Treatys, Declarations of War, Manifestos, and Other Publick Papers, Relating to Peace and War,

among the Potentates of Europe, from 1648 to the Present Time, 4 vols (1710–1732), include the Dutch

manifesto against Britain, 2 August 1652 (vol. 3, at 45), the British declaration of war against the Dutch

Republic, March 1672 (vol. 4, at 254), the Dutch declaration of war against France, 9 March 1689 (vol.

1, at 256), the British declaration of war against France, 4 May 1702 (vol. 1, at 421)and the French

declaration of war against Spain, 1719 (vol. 4, at 382). State practice also reected dualism to the extent

that states, in the application of the laws of war or when making peace, did not rehearse the language

of just war and acted as if all belligerents had an equal right to wage war, thus factually operating under

the logic of legal war. The conspicuous absence of any attribution of guilt and the general appearance of

amnesty clauses in early modern peace treaties illustrate this well. See note 77 below.

F.A.J. Szabo, The Seven Years War in Europe 1756–1763 (2008), at 36–40.

P. Paret, Frederick the Great: AHistorical Prole (1970), at 105–106. For a brief discussion of historiogra-

phy, see T.Blanning, Frederick the Great: King of Prussia (2015), at 597–601.

784 EJIL 29 (2018), 773–808

reputation, both among his enemies and later historians.

Recently, James Whitman

has argued that, although the justication Frederick II offered for his seizure of Silesia

seems far-fetched to most modern observers, he remained within the safe connes of

legal war through the single act of offering it. However insincere his revival of old

dynastic rights to parts of the Duchy of Silesia may appear, it did sufce to offer a plat-

form to his supporters and allies to claim the justice of his cause.

In truth, Frederick

II just about toed the line of legality with his invasion of 1740. It was only after his

armies had entered Silesia that he took the need to publish a plausible justication

seriously. Before, the king had proven quite derisive of the attempts of his ministers

to draft a justication and convince him of the signicance thereof.

The exploita-

tion of this neglect by the Viennese government alerted him to the danger.

On 31

December 1740, the Prussian government issued a manifesto laying claim to part of

the Duchy of Silesia, which it reasoned the Austrians unjustly occupied. This gave

Frederick II just cause and a right to secure his inheritance. The manifesto insisted, as

Frederick had done before in his communication with the court at Vienna, that he had

no aggressive or expansionist intentions against the Austrian Habsburgs.

Writing in 1757 at a time when he had given up all prospect of a career in the

service of his suzerain, King Frederick II, and was working for the elector of Saxony

and king of Poland, August III the Strong (1696–1763),

even Vattel conceded that

Frederick had acted within the connes of the law of nations back in 1740.

This

was, however, not the case for his invasion of Saxony in 1756. In a letter to the gov-

ernment of Bern, to which he was accredited as a diplomat, Vattel virulently protested

Frederick’s attack on his master’s lands. In his letter, Vattel argued that there were

only two just causes for war: redress for injury after an appeal to the enemy to ren-

der satisfaction had failed or the need to defend one’s security. As no complaint for

injury had been lodged against the elector of Saxony and Saxony had made no threat-

ening preparations, the Prussian king lacked any credible pretext for war. Moreover,

Frederick II had protested his friendship for Saxony and, one day before his invasion,

had requested passage for his troops. Vattel concluded that the Prussian king’s real

G. Ritter, Frederick the Great: AHistorical Prole (1968), at 80–81; T.Schieder, Frederick the Great (2000),

at 80–99; D.Showalter, The Wars of Frederick the Great (1996), at 39.

Whitman, supra note 21, at 54–55, 67–76, 119–132.

The much-quoted quip about an earlier memoir as ‘the work of a good charlatan’ (‘bravo, c’est l’ouvrage

d’un bon charlatan’) was not widely known among Frederick’s contemporaries. It was written on a draft of

28 November 1740. A.Berney, Friedrich der Grosse: Entwicklungsgeschichte eines Staatsmannes (1934), at

123; also W.F. Reddaway, Frederick the Great and the Rise of Prussia (1904), at 89–92; Schieder, supra note

50, at 84.

Schieder, supra note 50, at 99.

Mémoire sur les raisons qui ont déterminé le Roi à faire entrer ses troupes en Silésie, reprinted in R.Koser

(ed.), Preussische Staatsschriften aus der Regierungszeit König Friedrichs II (1740–1745) (1877) 74;

D.Fraser, Frederick the Great: King of Prussia (2000), at 78.

Emer de Vattel to Jean Henri Samuel Formey, 17 February 1757, reprinted in A.Bandelier (ed.), Emer de

Vattel à Jean Henri Samuel Formey: Correspondances autour du Droit des Gens (2012), at 179–180.

Vattel, supra note 25, at 2.18.335.

Aggression before Versailles 785

motive was his desire to acquire a rich country and rob it of its resources and man-

power. Such behaviour jeopardized the surety of all and made peace impossible.

This time, King Frederick II was aware of the precariousness of his legal position and

the urgent need to offer a credible defence of his action. In truth, although Frederick

II was the rst to resort to force in 1756, this was not a war of his choice. During the

summer of 1756, Frederick II had become – not without cause – convinced that his

main enemies, Austria and Russia, were preparing an offensive against him. Ever since

the Peace of Aachen, which put an end to the war of Austrian succession and secured

Frederick’s possession of Silesia,

Vienna had been plotting its reconquest. To this

purpose, it could count on the active cooperation of Saint Petersburg and the enmity

of Saxony for Prussia. But Vienna also needed to secure the alliance, or at least the

neutrality, of Prussia’s traditional ally, France.

After years of failure, Maria Theresia

and her chancellor, Count Wenzel Anton von Kaunitz (1711–1794), nally achieved

their goal in the spring of 1756. Already in the summer of 1755, the likelihood of a

colonial war against Britain over North America had convinced France of the neces-

sity to obtain Austria’s neutrality so that France could avoid becoming embroiled in a

Europeanwar.

However, all through the autumn of 1755, the French King Louis XV (1710–1774)

had proved reluctant to blow up his alliance with Prussia and betray King Frederick II,

as much as he might dislike him and reproach him for his repetitive perdy. The news

of the Convention of Westminster of 16 January 1756, whereby Britain and Prussia

agreed to neutralize Germany from the war between Britain and France, caused Louis

XV to change tack.

In February 1756, the decision was taken at Versailles not to

prolong the alliance with Prussia after its expiration in June 1756, although the

French king still refused to listen to any proposals that were directed against Prussia.

Nevertheless, with the First Alliance of Versailles, signed on 1 May 1756, he effect-

ively abandoned his ally to the designs of Vienna and Saint Petersburg. The Versailles

agreement included a treaty of defensive alliance, which obliged France and Austria

to aid one another with a corps of 24,000 men in case of attack.

Letter of 28 February 1757, reprinted in Bandelier, supra note 55, at 181–184.

Treaty of Peace of Aachen 1748, 38 CTS 297.

McGill, ‘The Roots of Policy: Kaunitz in Italy and the Netherlands, 1742–1746’, 1 Central European

History (1968) 131; L.Schilling, Kaunitz und das Renversement des alliances: Studien zur aussenpolitischen

Konzeption Wenzel Antons von Kaunitz (1994); Pommerin and Schilling (eds), ‘Denkschrift des Grafen

Kaunitz zur Mächtepolitischen Konstellation nach dem Aachener Frieden von 1748’, in J.Kunisch etal.

(eds), Expansion und Gleichgewicht: Studien zur europäischen Mächtepolitik des ancient regime (1986) 165.

40 CTS 291.

Treaty of Alliance of Breslau 1741, 36 CTS 217.

40 CTS 335, Art. 7; Blanning, supra note 49, at 193–202; Bély, ‘La politique extérieure de la France au

milieu du XVIIIe siècle’ in S.Externbrink (ed.), Der Siebenjährige Krieg (1756–1763): Ein europäischer

Weltkrieg im Zeitalter der Aufkläung (2011) 75; S.Externbrink, Friedrich der Grosse, Maria Theresia und

das Alte Reich: Deutschlandbild und Diplomatie Frankreichs in Siebenjährigen Krieg (2006) 107–10; Fraser,

supra note 54, at 287–310; F.Masson (ed.), Mémoires et lettres de François-Joachim de Pierre, Cardinal de

Bernis (1715–1758) (1878), vol. 2, at 222–275; W. Mediger, Moskaus Weg nach Europa: Die Aufstieg

Russlands zum europäischen Machtstaat im Zeitalter Friedrichs der Grossen (1952), at 453–637; Pommerin,

786 EJIL 29 (2018), 773–808

It took until June 1756 before King Frederick II realized the impact of the Versailles

agreement. Even if he did not know the full details of the treaties made between

Versailles and Vienna, what he knew, and the reports he received from his spies of

the Austro-Russian plans and preparations, convinced him that France had aban-

doned him to his enemies. Realizing the bleakness of his situation, Frederick decided

to gamble on a quick offensive against Austria, hoping to knock it out of the war before

Russia could bring its numeric weight into the equation.

The news that the Austro-

Russian attack had been postponed to 1757 only strengthened his resolve. By late July,

Frederick had decided to attack in late summer so as to prevent Russian interference

in 1756. He also included the invasion of Saxony in his plan. Securing the electorate

would strengthen the defences of Brandenburg and enhance his demographic, logis-

tic and tax basis for the duration of the war. From the perspective of justication, the

invasion of Saxony was his weak spot. It would lay Frederick II bare to accusations

of expansionism. Although the Prussian king was ascertained of the enmity of the

Saxon government and suspected its collusion with Vienna and Saint Petersburg in

the planned attack, he had no proof of the latter. The search of the electoral archives

after the invasion would not deliver a smoking gun either.

If King Frederick II had good reasons to worry about the outfall of his planned attack

throughout Europe for his reputation and general standing, there were also two more

concrete motivations for the care he took this time in arguing his case to the world.

First, Frederick needed to avoid a condemnation of his actions by the Diet of the Holy

Roman Empire, which might lead to the declaration of an imperial war against him

and even to the pronunciation of an imperial ban, which would mean his deposition

in his German lands.

Second, and more importantly, he needed to avoid triggering

the defensive alliance between Austria and France. Thereto, he had to leave the court

of Versailles enough leeway so that it could claim – if it chose to – that the Prussian

attack on Austria did not constitute an act of aggression covered by the alliance.

‘Bündnispolitk und Mächtesystem: Österreich und der Aufstieg Russlands im 18. Jahrhundert’ in

Kunisch etal., supra note 59, 113; Reddaway, supra note 52, at 189–205; Rödel, ‘Eine geheime fran-

zösische Initiative als Auslöser für das Renversement des Alliances?’, in Kunisch et al., supra note 59,

97; Schieder, supra note 50, at 117–120; A.von Arneth, Geschichte Maria Theresias (1870), vol. 4, at

354–494; R.Waddington, Louis XV et le renversement des alliances: Préliminaires de la Guerre de Sept Ans

1754–1756 (1896), at 287–359.

Letter of King Frederick II to D.H.von Knyphausen, 8 June 1756, 12 June 1756; to A.Mitchell, 22

June 1756; to D.Knyphausen, 22 June 1756, 26 June 1756, reprinted in J.G. Droysen (ed.), Politische

Korrespondenz Friedrich’s des Grossen (1879–1939), vol. 12, at 394, 400–401, 441–442, 442–443,

465–467; Letter of H.G.von Podewils to A.F. Eichel, 22 July 1756; Letter of King Frederick II to Baron

Klinggraeffen, 24 July 1756, reprinted in Droysen, ibid., vol. 13, 104–107, 114–115.

The rst would transpire, the second not; Externbrink, supra note 62, at 111–130; K.A.von Aretin, Das

Alte Reich 1648–1806 (1997), vol. 3, at 88–100; Wilson, ‘Prussia’s Relations with the Holy Roman

Empire’, 51 HJ (2008) 337, at 350–352.

Letter of King Frederick II to D.H.von Knyphausen, 26 July 1756; Letter of Podewils to King Frederick II,

26 July 1756; Letter of Knyphausen to King Frederick II, 10 September 1756, reprinted in Droysen, supra

note 63, vol. 13, at 128–130, 133, 424.

Aggression before Versailles 787

King Frederick II prepared the ground well for the presentation of his case. During

July and August 1756, he had his representative at Vienna ask the empress three times

for assurances that she was not preparing an attack on him. The second and third

time, he promised that he would not open hostilities if Maria Theresia guaranteed she

would not attack in 1756 or 1757. Frederick hoped that her refusal to give this guar-

antee would deect the blame.

At the time of the invasion of Bohemia in September,

the Prussian government issued a manifesto that was translated in different languages

and widely spread. The manifesto, which was from the hand of Frederick II himself,

had gone through no less than six revisions since mid-July.

Because the Prussian king could neither invoke serious injury nor unwarranted

attack on the Austrian side, he argued preventive self-defence. In the manifesto, he

sailed as close to traditional just war discourse as possible. First, the manifest opposed

the relentless desire of Austria to harm Prussia with the latter’s long suffering thereof.

In this context, Frederick accused Austria of having violated a commercial clause

from the Peace of Breslau from 28 July 1742.

Although this constituted a ‘pre-

text for legitimate war’, it paled in comparison to the many other transgressions of

Vienna. Second, the manifesto presented Austria’s desire to bring down Prussia as a

rst step towards the realization of its ambition to dominate Germany, root out the

Protestant religion and destroy the liberty of the princes and estates of the empire.

Thereby, he invoked the traditional discourse of the Protestant-French alliance that

went back to the days of Emperor Charles V (1500–1558). Although he did not men-

tion it in this context, King Frederick II thus hoped to stoke up the concerns that the

alliance between the two leading Catholic powers of Europe, France and Austria had

caused among Protestants.

Third, the manifesto argued that Austria was planning

and preparing an attack on Prussia. It detailed the different steps Austria had taken to

build a coalition against Prussia and listed its military preparations. It also rehearsed

the fruitless triple attempt by Frederick to avert war by requesting a guarantee that

he would not be attacked before the end of the coming year. This and the denial of

any preparations against Austria on Prussia’s part had to lock the case of preventive

self-defence.

The manifesto closed with a remarkable passage, which directly referred to aggres-

sion. In it, the Prussian king conceded that he was the one to commence hostilities.

However, this did not equal aggression. According to him, aggression only referred

Letter of Baron Klinggraeffen to King Frederick II, 18 July 1756, 27 July 1756, 7 August 1756, 24 August

1756; Minutes of the conversation of King Frederick II with A.Mitchell, 26 August 1756, reprinted in

Droysen, supra note 63, vol. 13, 90–91, 163, 209, 285–291. Fraser, supra note 54, at 310–313; Lüth,

‘Frederick the Great and the First World War’, in M.H. Danley and P.J. Speelman (eds), The Seven Years’

War: Global Views (2012) 1, at 1–2; Schieder, supra note 50, at 88.

Exposé des motifs, qui ont obligé Sa Majesté le Roi de Prusse, à prévenir les desseins de la cour de Vienna,

in O. Krauske (ed.), Preussische Staatsschriften aus der Regierungsziet König Friedrichs II (der Beginn des

Siebenjährigen Kriegs) (1892), at 133–183.

36 CTS 409, Art.8.

Burckhardt, ‘Religious War or Imperial War? Views of the Seven Years’ War from Germany and Rome’, in

Danley and Speelman, supra note 66, 107.

788 EJIL 29 (2018), 773–808

to ‘every act which is diametrically opposed to a treaty of peace’. The making of an

offensive alliance, the exhortation of other states to attack another, designs to invade

another state or a sudden attack were examples of aggression, even if only the last one

implied resort to force. ‘Whoever prevented such aggressions, could be the one who

commenced hostilities, but was not the aggressor’, Frederick concluded.

In sum, the

real aggressor was Vienna, which had violated the Peace of Breslau, incited Russia to

attack Prussia and prepared for invasion itself.

King Frederick II’s manifesto was cleverly designed to kill two birds with one stone.

He presented Austria’s design on Prussia as a rst step towards the destruction of lib-

erty and Protestantism in the empire in the hope of deecting a condemnation by

the Diet. In this, time would prove him partially successful. Furthermore, he wanted

to counter the accusation that he was guilty of an unwarranted attack, which he

labelled aggression, on Austria for this would trigger the Alliance Treaty of Versailles.

Frederick’s manifesto, his later writings and his diplomatic offensive failed to attain

this latter goal. Already on 26 July 1756, the French ambassador at the Prussian

court had warned Frederick II that an attack on Austria would trigger the Alliance of

Versailles.

Upon Vienna’s invocation of the treaty in the autumn, it decided to send

the promised auxiliary corps of 24,000. Worse was to follow. Ever since the closure of

the Versailles agreement, Austrian diplomacy had relentlessly pursued its attempts of

further committing France to its design against Prussia. However, powerful factions

at the French court resisted this either because they held to the ‘old system’ of enmity

with Austria and friendship with the German Protestants or because they prioritized

the colonial and maritime war against Britain over any embroilment on the continent.

The failed assassination attempt against the life of King Louis XV in January 1757

caused a chain of events that led to the fall of some leading opponents of a closer alli-

ance with Vienna. This set the wheels in motion towards France’s full participation in

the anti-Prussian alliance.

The outcome of this was the Second Treaty of Versailles of 1 May 1757. Contrary

to its predecessor, this was an offensive alliance. Remarkably, the designs of the allies

were justied as a reaction against the ‘unjust aggressor’ King Frederick II of Prussia.

Its stipulated goals were to repel the aggressor and to procure satisfaction as well as

security for the future for both Austria and Saxony.

The treaty constituted a bilateral

agreement between France and Austria, but the signatories invited Russia, Sweden,

Poland-Saxony, Bavaria, the Palatinate, Spain and the Italian Bourbons to join the

alliance and reap its benets. Although negotiations with these powers still had to

take place, the treaty stipulated the conditions of their adherence and the benets they

‘Exposé de motifs’, supra note 67, 180.

Letter of H.G.von Podewils to King Frederick II, 26 July 1756, reprinted in Droysen, supra note 63, vol.

13, at 133.

Bély, supra note 62, at 86–91; Masson, supra note 62, vol. 2, at 281–375; M.Hochedlinger, Austria’s Wars

of Emergence 1683–1797 (2003), at 335–337; von Arneth, supra note 62, vol. 5, at 57–144.

41 CTS 1, Preamble (Second Treaty of Versailles).

Aggression before Versailles 789

would obtain from it. Versailles and Vienna styled their alliance as an action on behalf

of the whole community of European princes.

The treaty, which went partly back to a design of the Saxon government from

1744,

was textbook Vattel. It attached two major consequences to Prussia’s con-

demnation as an unjust aggressor. First, it provided for the compensation of Saxony

for the damages it had suffered in consequence of its ‘unjust invasion’ and ‘cruel dev-

astation’.

Second, the treaty partners proposed not only the reconquest of Silesia but

also the dismantling of Prussia. King Frederick II would be stripped of almost all of

his lands, which were to be distributed among his enemies. Only its historic core, the

Electorate of Brandenburg, was to be left. This was justied on the basis of the need

to weaken the Prussian king in order to secure the peace and tranquillity of Europe.

The Second Treaty of Versailles was exceptional, not so much in using the discourse

of just war but, rather, in envisioning the effective sanctioning of its transgressor. The

intentions of the allies contradicted standard practices of peace making. Whereas dur-

ing the early modern age princes and governments commonly used the language of

just war when resorting to war, peace treaties never did.

There is not a single peace

treaty among European sovereigns from the 17th or 18th centuries that contains an

express, or even implicit, concession by a belligerent that he had waged an unjust war.

Moreover, the peace treaties from this period commonly include an amnesty clause,

by which the signatories waived all rights to compensation for themselves and their

subjects for any damage pursuant to the war, whether legal or illegal, just or unjust.

By the mid-18th century, these clauses were considered to be automatically implied.

The Second Treaty of Versailles, for all its bold statements and ambition, would not

lead to any different result.

It was never ratied by Austria and was formally lifted, as

a result of a change of policy at the French court, by the Third Treaty of Versailles of

30 December 1758.

Nevertheless, it indicated that the discourse of just war, includ-

ing the concept of aggression as an aggravated, manifest violation of it, was part of

the lore and practice of the public law of Europe.

4 International Use of Force Law in the Century before

World WarI

The perusal of legal scholarship and state practice of the 19th century, when read

against the backdrop of the early modern doctrine on which it was built, surely forces

M.S. Anderson, The War of the Austrian Succession 1740–1748 (1995), at 135; R.Hanke, Brühl und das

Renversement des alliances: die antipreussische Aussenpolitik des Dresdener Hofes, 1744–1756 (2006).

Second Treaty of Versailles, supra note 73, Art.8.

Ibid., Preamble and Arts 5–6.

R. Lesaffer, Europa, een zoektocht naar vrede? (1453–1763/1945–1997) (1999), at 443–452.

Fisch, supra note 45; Krieg und Frieden im Friedensvertrag: Eine universalgeschichliche Studie über Grundlagen

und Formelemente des Friedensschlusses (1979), at 92–112; Lesaffer, ‘Peace Treaties and the Formation of

International Law’ in Fassbender and Peters, supra note 5, 71, at 87–89.

Treaty of Peace of Hubertusburg 1763, 42 CTS 361, Art.1.

41 CTS 235; Bély, supra note 62, at 91–92.

790 EJIL 29 (2018), 773–808

one to amend the prevalent view that 19th-century international law barely held

restrictions on the right to resort to force and war. Although the restrictive norma-

tive power of the jus ad bellum was diminished and the rules were relaxed during the

century stretching from the Congress of Vienna to World War I, the important point is

that traditional doctrine survived to a much larger extent than is commonly accepted.

This included the concept of aggression as a major violation of the jus ad bellum. Even

more so, during the 19th century, the concept gained a wider meaning as well as a

new prominence.

At rst sight, it seems logically inevitable that the ascendancy of positivism and

the ejection of natural law from the ambit of international law by the late 19th cen-

tury caused the demise of just war.

This only left the concept of legal war, which,

detached from just war, boiled down to a mere acceptance of the right of states to

resort to war whenever they saw t. It left international law with nothing to do but to

recognize war as a factual state, of which it could regulate the legal effects but not the

legality. However, as Verdebout has argued, only a few scholars from around the turn

of the 20th century actually defended this position.

Although there are a few more

of these radical positivists than the four Verdebout identies, their interpretation was

not representative of the whole period nor did it sweep the board in the early years of

the 20th century.

It was only after World War Ithat these authors came to be seen

as representative.

Some international lawyers from the rst three-quarters of the 19th century con-

tinued to adhere to the dualism of natural and positive law and of just and legal war.

But, even after legal positivism took hold and pushed natural law to the margins at

the end of the century, only a minority adopted the indifference thesis. The majority,

while pushing natural law outside the ambit of law, recycled many of its institutions

and doctrines back into positive international law. Their reduction of international

law to positive law was largely a theoretical move, which did not necessarily reect

in substance. The redenition of the right of self-defence of states from a natural to a

In recent years, scholars have debated the impact of positivism of 19th-century international law. The

old view that the whole century was an era of positivism needs to be nuanced. The dualism or co-exis-

tence of natural and positive law of nations persisted deep into the century. Nevertheless, during the nal

three decades of the century positivism took hold. Generally, positivists did not reject the existence of

natural law, but they denied it any normative value in practice and reduced their understanding of inter-

national law to that of positive international law. See M.García-Salmones Rovira, The Project of Positivism

in International Law (2013), at 30–34; Neff, supra note 15, at 241–260; Sylvest, ‘International Law in

Nineteenth-Century Britain’, 75 BYIL (2004)9.

Verdebout, supra note 10.

A. Hershey, The Essentials of International Public Law (2nd edn, 1918), at 349–352; V.Stockton, Outlines

of International Law (1914), at 294. There are also authors who dismissed restrictions on war out of

hand. See, e.g., R.von Mohl, Staatsrecht, 2 vols (1860), vol. 1, at 765.

W.O. Manning, Jr., Commentaries on the Law of Nations (1839), at 57–67; R.Phillimore, Commentaries

upon International Law, 3 vols (1854–1857), vol. 1, 55–85; J. Reddie, Inquiries in International Law,

Public and Private (2nd edn, 1851), at 111–133; T.Twiss, The Law of Nations Considered as Independent

Communities, 2 vols (2nd edn, 1884), vol. 1, 145–177; T.Woolsey, Introduction to the Study of International

Law, Designed as an Aid in Teaching, and in Historical Studies (1860), at 17–21.

Aggression before Versailles 791

customary right offers a good example thereof. Mainstream positivists recycled much

of old just war thought back into their newly unied category of international law,

collapsing the distinction between just and legal war in the process. The major devel-

opment of the jus ad bellum of the 19th century, in the end, pertained rather to its

theoretical framing than to its material content.

Whereas it is readily acknowledged that the right to resort to war or force was inher-

ent to statehood itself under 19th-century international law, it is often forgotten that

the opposite was also true. Force and war were also considered to be, in principle,

violations of the inherent rights of states. It was through the category of fundamen-

tal or inherent rights of states that the just war tradition was recycled into modern

international law. The vast majority of the writers of international law textbooks from

the period distinguished between fundamental and conditional rights. Fundamental

rights were inherent to statehood itself, while conditional rights arose from the deal-

ings between states. The theory predated the ascendancy of positivism. It had its roots

in early modern doctrine and became common over the early 19th century. It was

even shared by proponents of the indifference thesis.

Dualists from the early 19th

century acknowledged that fundamental rights derived from natural law.

Later, pos-

itivist writers would sometimes quip that their predecessors had mistakenly believed

so. However, they judged them to be an integral part of their solitary category of –

positive – international law.

Avariety of fundamental rights was proposed, but most

writers would agree – under whatever heading – on the rights to existence, self-pres-

ervation, internal sovereignty, external independence, equality and dignity. To these

corresponded a concomitant duty of other states to respect the fundamental rights

of another state. Logically, the use of force against a state, including war, constituted

a violation of one or more of the fundamental rights – generally, that of existence or

dignity – of the targetstate.

Force and war were violations of international law and, in principle, illegal. Such

violation could only be legitimized on the basis of the superseding right of self-preser-

vation. With the right to existence came the right for a state to do whatever was nec-

essary to preserve itself, its sovereignty, independence and dignity. This included the

protection of its rights, vital interests and honour. In this way, the core principles of

the just war doctrine were reconstructed under the heading of the fundamental rights

of states. The basic reasoning was that force and war were prohibited, except when

Hershey, supra note 83, at 143–145; T.J. Lawrence, The Principles of International Law (1895), at 109–

111; Stockton, supra note 83, at 62–63; J.Westlake, International Law (2nd edn, 1907–1910), vol. 1, at

300–301. Oppenheim rejected the distinction but brought fundamentals rights in through the backdoor

as customary rights, L.Oppenheim, International Law: ATreatise (2nd edn, 1912), vol. 1, at 165–166.

H.W. Halleck, International Law, or Rules Regulating the Intercourse of States in Peace and War (1861), at

81–82; Twiss, supra note 84, at 178; Woolsey, supra note 84, at 17–32. Some derived them directly from

divine will. D.Gardner, A Treatise of International Law and a Short Explanation of the Jurisdiction and Duty of

the Government and the Republic of the United States (1844), at 87–89.

J.de Louter, Le droit international public positif (1910 [translated in1920]), vol. 1, at 233; Hershey, supra

note 83, at 143; A.Mérignac, Traité de droit public international (1905–1912), vol. 1, at 233–235; E.von

Ullmann, Völkerrecht (2nd edn, 1908), at 141.

792 EJIL 29 (2018), 773–808

necessary for a state to preserve itself. Whereas most writers cast the right to force

and war in terms of the supersession of the right to existence of the one state by the

right to self-preservation of another, some authors – in particular, German authors –

preferred to appeal to extra-legal notions of emergency and necessity, which allowed

the side-lining of the rights of other states. Although these authors considered war to

be a state of fact rather than of law, the concrete acceptable causes for war that they

proposed were not materially different.

To all of this, most writers added that force

and war could only be resorted to after ways to settle the dispute peacefully had failed

or had been refused.

Some authors did not explicitly state that war and force were violations of law

in principle, but the implication was clear from their reasoning about fundamental

rights and the role of self-preservation, numerous remarks about which legitimiza-

tions of war were acceptable and the whole structure of their work. Commonly, war

was discussed as the last of the various means of dispute settlement. In addition to

A. Anzilotti, Corso di diritto internazionale (1912), at 302–303; A.Bello, Principios de derecho de jentes (3rd

edn, 1873), at 23, 147; J.C. Bluntschli, Das moderne Völkerrecht der civilisirten Staaten: als Rechtsbuch dar-

gestellt (1868), at 84–91, 287; H.Bonls and P.Fauchille, Manuel du droit international public (droit des

gens) destiné aux étudiants de droit et aux aspirants aux fonctions diplomatiques et consulaires (4th edn, 1905),

at 123–127, 517, 575; A.von Bulmerincq, Völkerrecht oder internationales Recht (1884), at 202–203,

357; P.Fiore, Il diritto internazionale codicato e la sua sanzione giuridica (1890), at 103, 300; de Louter,

supra note 87, vol. 1, at 241–248; T.Funck-Brentano and A.Sorel, Précis du droit des gens (2nd edn,

1887), at 32–46, 232–236; Gardner, supra note 84, at 87–94, 204–206; C.Gareis, Institutionen des

Völkerrechts (1888), at 80–82, 192; W.E.R. Hall, International Law (1880), at 13–53, 226–227; Halleck,

supra note 86, at 91–93, 313; A.W. Heffter, Das europäisches Völkerrecht des Gegenwart (3rd edn, 1855),

at 47–53, 191–192, 199–203; Kent, ‘On the Law of Nations’, in J.Kent, Commentaries on American Law

(1826), vol. 1, 1, at 21–48, 181; J.-L. Klüber, Droit des gens moderne de l’Europe avec un supplément con-

tenant un bibliothèque choisie du droit des gens (1861), at 57–60, 64–56, 116–117, 299–305; Lawrence,

supra note 85, at 109–120; F.von Liszt, Das Völkerrecht systematisch dargestellt (2nd edn, 1902), at 41–55;

J.Lorimer, The Institutes of the Law of Nations: ATreatise of Jural Relations of Separate Political Communities

(1883–1884), vol. 2, at 18–42; H.S. Maine, International Law: ASeries of Lectures Delivered before the

University of Cambridge 1887 (1888), at 59–64, 210–211; F.F. Martens, Traité de droit international

(1883–1887), vol. 1, at 387–391; G.F.von Martens, Précis du droit des gens moderne de l’Europe fondé sur

les traités et les usages: Pour servir d’introduction à un cours politique et diplomatique (3rd edn, 1821), at 219–

221, 449–451; Mérignac, supra note 87, vol. 1, at 236–242, vol. 2, at 9–11; H.B. Oppenheim, System

des Völkerrechts (1845), at 85–86, 152; Oppenheim, supra note 85, vol. 1, at 166–188; Phillimore, supra

note 84, vol. 1, at 149–189, vol. 3, at 99–103; R.M.de Damau de Olivart, Tratado de derecho internacional

public (1903–1904), vol. 1, at 233–235; P.Pradier-Fodéré, Traité de droit international public européen et

américain suivant les progrès de la science et de la pratique contemporaines (1885–1906), vol. 1, at 283–284,

307, 358–366, 382–384, 413–414, vol. 6, at 507–508; Reddie, supra note 84, at 185–181, 211–215;

A.Rivier, Principes du droit des gens (1896), vol. 1, at 27–29, 255–275; F.Saalfeld, Handbuch des positiven

Völkerrechts (1833), at 62–63, 190–192; Twiss, supra note 84, vol. 1, at 178–183, vol. 2, at 4–5, 51–54;

Ullmann, supra note 87, at 146–149; Westlake, supra note 85, vol. 1, at 307–315; H.Wheaton, Elements

of International Law: With a Sketch of the History of the Science (1836), vol. 1, at 75–76, 309–312; G.G.

Wilson, Handbook of International Law (1910), at 55–56; Woolsey, supra note 84, at 32–37.

Bluntschli, supra note 88, at 270; Hall, supra note 88, at 51; de Louter, supra note 87, vol. 2, at 215; Halleck,

supra note 86, at 289; Liszt, supra note 88, at 289; G.F. Martens, supra note 88, at 432; E.Nys, Le droit inter-

national: les principes, les théories, les faits (1904–1906), vol. 3, at 83; Reddie, supra note 84, at 216; T.A.H.

Schmalz, Das europäisches Völker-Recht in acht Büchern (1817), at 212; Twiss, supra note 84, vol. 2, at 54; T.A.

Walker, Manual of Public International Law (1895), at 23–25; Wilson, supra note 88, at 94.

Aggression before Versailles 793

these general expositions on force and war, most authors expressly and elaborately

debated the question of the legality of a single category of the use of force: interven-

tion. Although, in 19th-century doctrine and practice, the term was frequently used

with little discrimination, in the context of a discussion on fundamental rights in

textbooks of international law, it generally signied the use of force for the purpose

of coercing a state to change its constitution, policy or concrete behaviour. The vast

majority of international lawyers expressly labelled this a violation of the right of

independence of states and of the corresponding duty of non-interference. Only in

exceptional circumstances could intervention be condoned. Many textbooks featured

an elaborate discussion of state practice with regard to intervention, distinguishing

legal from illegal forms. The subject generated much attention, certainly when com-

pared to the question of legality of war and other measures of war, because it was

contentious. In the end, no complete consent was reached in literature. Whereas most

authors could agree on the legality of interventions that were necessary to preserve

the existence, independence, rights, vital interest or honour of the intervening state –

which, in fact, is a restatement of the key elements of just war – or on the legality of

interventions in the case of invitation by the other state, no unanimity was reached

on humanitarian or religious intervention, regime change or action to uphold the bal-

ance of power against the aggrandizement of a certain power.

In all, international lawyers of the 19th and early 20th centuries sustained the two

classical legitimizations for war, self-defence and redress of injury, but, at the same

time, made four changes to the material content of traditional jus ad bellum. First, in

particular, mainstream positivists largely surrendered the distinction between just

and legal war – between war as a form of self-help after injury and war as a means of

A. Amos, Lectures on International Law: Delivered in the Middle Temple Hall to the Students of the Inns of

Court (1874), at 37–41; M.Bernard, On the Principle of Non-Intervention: ALecture Delivered in the Hall of

All Souls’ College (1860); F.E. Birkenhead, International Law (2nd edn, 1903), at 46–51; Bluntschli, supra

note 88, at 26–27, 97–98; Bonls and Fauchille, supra note 88, at 140–143; C.Calvo, Le droit interna-

tional théorique et pratique, précédé d’un exposé historique des progrès de la science du droit des gens (2nd edn,

1870–1871), vol. 1, at 224–238, 308–309; Heffter, supra note 88, at 53–56; Klüber, supra note 88,

at 61–63; de Louter, supra note 87, vol. 1, at 250–258; F.Despagnet, Cours de droit international public

(3rd edn, 1905), at 221–238; Funck-Brentano and Sorel, supra note 88, at 212–221; Gareis, supra note

88, at 82–84; Halleck, supra note 88, at 82–87, 315–317, 334; Hershey, supra note 83, at 147–153;

Lawrence, supra note 85, at 119–120; Liszt, supra note 88, at 55–58; F.F. Martens, supra note 88, vol.

1, at 393–398; Mérignac, supra note 87, vol. 1, at 244–301; Oppenheim, supra note 88, at 161, 222–

224; Olivart, supra note 88, vol. 1, at 239; Phillimore, supra note 84, vol. 1, at 314–329; Pradier-Fodéré,

supra note 88, vol. 1, at 424–434, 474–475; Reddie, supra note 84, at 192–198, 390–393; Rivier, supra

note 88, vol. 1, at 390–403; Saalfeld, supra note 88, at 62–63; Ullmann, supra note 87, at 454–460;

Walker, supra note 89, at 23–25; Wheaton, supra note 88, at 77–100; Wilson, supra note 88, at 57–65;

see also S.Chesterman, Just War or Just Peace? Humanitarian Intervention and International Law (2001),

at 35–42; Segesser, ‘Humanitarian Intervention and the Issue of State Sovereignty in the Discourse of

Legal Experts between the 1830s and the First World War’ in F.Klose (ed.), The Emergence of Humanitarian

Intervention: Ideas and Practice from the Nineteenth Century to the Present (2015) 56; Vec, ‘Intervention/

Nichtintervention: Verrechtlichung der Politik und Politisierung des Vökerrechts im 19. Jahrhundert’, in

U.Lappenküpper and R.Marcowicz (eds), Macht und Recht: Völkerrecht in den internazionalen Beziehungen

(2010) 135.

794 EJIL 29 (2018), 773–808

dispute settlement. Most authors were aware of the historical pedigree of the distinc-

tion, and many reiterated that it was the impossibility to discern among sovereign

states which belligerent had right on its side that made it necessary to treat both bel-

ligerents equally under the laws of war. But they stopped considering them separate

legal categories that applied in different dimensions and generated different legal con-

sequences. To them, the distinction between self-help after injury and dispute settle-

ment was one of perspective. Whereas the belligerents themselves considered the war

an action of legal enforcement after injury, it generally appeared to be an instrument

of dispute settlement from the perspective of objective international law or neutral

observers.

Second, the inclusion of the right of dignity among the fundamental rights of

states, either as an autonomous right or as an expression of the right to existence,

reected the century’s concern for princely and national honour. It became quite

common among 19th-century international lawyers to label the protection or resto-

ration of honour a just cause for war next to the protection or restoration of a right.

Third, founding the right to force or war on the fundamental right of self-preservation

extended the ambit of self-defence. Here, the imprint of Vattel became clear. It made

the protection of a state’s security a major, legitimate concern of states. This led to the

legitimization of anticipatory self-defence against threats to a state’s security. Because

war could only be allowed when there was no alternative left, this was generally under-

stood to mean an imminent threat. The correspondence between the British and US

foreign secretaries on the Caroline incident (1837) became the classical statement of

this rule in Anglo-American literature.

Lastly, the prominence of self-preservation

led to another extension of the right to resort to war – namely, to wars about the vital

interests of states. This debased the legal nature of the whole fabric of jus ad bellum. It

was, however, a contentious point.

Nevertheless, this relaxation of classical just war

thought surely added to the feeling of crisis that surrounded existing international use

of force law by the turn of the 20th century.

These four changes allow for a categorization of wars in terms of their justication,

which came to replace the old distinction between just and legal war in the interna-

tional law of the late 19th and early 20th centuries: wars of self-preservation and

dispute settlement wars. The rst category contained not only wars to repel an actual

Bonls and Fauchille, supra note 88, at 146–147; Bulmerincq, supra note 88, at 205; Gareis, supra note

88, at 86; Halleck, supra note 88, at 313; Liszt, supra note 88, at 59–60; F.F. Martens, supra note 88, vol.

1, at 402–404; Rivier, supra note 88, vol. 1, at 256; Woolsey, supra note 84, at 190.

Bello, supra note 88, at 147; Gardner, supra note 88, at 204–205; Halleck, supra note 88, at 314–315;

Kent, supra note 88, at 47; Lawrence, supra note 85, at 118; F.F. Martens, supra note 88, vol. 1, at 388;

Phillimore, supra note 84, vol. 1, at 187; Twiss, supra note 84, vol. 1, at 181–182, vol. 2, at 3; Westlake,

supra note 85, vol. 1, at 312.

Anzilotti, supra note 88, at 303; Anzilotti, ‘Il concetto moderno dello stato ed il diritto internazionale’, in

Scritti di diritto internazionale pubblico (1914–1915) 619, at 621; Funck-Brentano and Sorel, supra note

88, at 231, 238; Liszt, supra note 88, at 276; Martens, supra note 88, vol. 1, at 391; Reddie, supra note 84,

at 212–213; Rivier, supra note 88, vol. 2, at 149; Ullmann, supra note 87, at 431. Some spoke out against

it, Bluntschli, supra note 88, at 291; Nys, supra note 89, vol. 3, at 107.

Aggression before Versailles 795

or imminent armed attack but also wars in reaction to a violation of the rights, inter-

ests or honour of states. The category encompassed the whole area of what used to

be just war, plus its expansion towards the protection or restoration of vital interests

and honour. Whereas only wars to repel an actual or imminent attack fell within the

connes of the traditional understanding of the right of self-defence as it originated

from natural law, the terms self-preservation and self-defence were increasingly con-

founded, particularly in state practice. The second category contained wars to settle a

dispute over rights, interests or honour. These categories were not two separate legal

regimes but, rather, were a reection of the argumentations in doctrine and practice.

The categorization was more a matter of perspective, except in clear cases of self-

defence against a prior armed attack. Whereas belligerents would often claim to ght

to enforce a violated right or interest under the invocation of self-preservation, the

war appeared to be a dispute settlement war to third parties.

By 1900, international use of force law was in disarray. Yet, contrary to what

modern historians have generally alleged, the basic tenets of the old just war doc-

trine largely survived in legal scholarship. The changes and challenges came less from

the substantial moves that had been made than from the radical alternation of the

intellectual context and theoretical framing of international law. This did not only

stem from the rise of legal positivism but also from the secularization of international

relations and law. Although many statesman, diplomats and lawyers still identied

European civilization with Christianity, the separation of religion and state after the

American and French Revolution forced international lawyers to cut their law loose

from its traditional, religious moorings.

Both positivism and secularization made

natural law and obligation in conscience appear as empty categories, which pertained

to the world of morality or political intentions but not to law. The new – positive –

international law that emerged was a much-reduced category compared to the old

dualist system of the law of nature and of nations.

By the end of the 19th century, international lawyers had become more critical and

sceptical of existing jus ad bellum. However, few international lawyers took the ulti-

mate consequence of ostracizing the just war tradition together with natural law from

the sphere of their international law.

But even those scarce radical positivists who

did so, such as Thomas Lawrence or Lassa Oppenheim, retained a far more sophis-

ticated doctrine of use of force than the thesis of indifference suggests. First, they

agreed with dualists and mainstream positivists that war and force were a violation

of the fundamental rights of states that were only exceptionally permissible. Second,

they retained the separation of just and legal war in two different spheres. In this, they

were straying closer to the dualist tradition than mainstream positivists were. In short,

Steiger, ‘From the International Law of Christianity to the International Law of the World Citizen:

Reections on the Formation of the Epochs of the History of International Law’, 3 JHIL (2001) 180, at

184–190.

Apart from the demise of natural law, social Darwinism has also been indicated as a cause for the indif-

ference thesis; Diggelmann, ‘Beyond the Myth of a Non-Relationship: International Law and World War

I’, 19 JHIL (2017) 93, at 98–102.

796 EJIL 29 (2018), 773–808

the radical positivists by and large rehearsed traditional doctrine, only to dismiss just

war as part of a moral or political discourse. The indifference thesis came from their

radical redenition of international law rather than from a substantial rewriting of

tradition doctrinal. It was their reduction of international law to positive, enforceable

rules that made them expel just war from the connes of the law. But, even if they just

mentioned it in order to state that it found itself outside the connes of the law, they

still aided in preventing it from falling into oblivion.

Mainstream positivists reacted to the challenge of natural law’s demise by trans-

ferring the just war doctrine back into their newly dened – positive – international

law and merging the justice and legality of war into one single category. However,

this reduced the normative strength of restrictions on war. Under early modern doc-

trine, a prince who waged an unjust, but legal, war might escape sanction in the here

and the now, but he knew that he would be threatened by divine sanction at the end

of times. Under the newly unied category of positive international law, the distinc-

tion between justice and legality collapsed. Awar was either legal or illegal. In both

cases, there was generally no possibility to sanction an illegal belligerent as there was

no one to render an objective judgment. Mainstream positivists just as much as radi-

cal positivists felt unease over this situation, and many of them looked for alternative

methods to restrict war, such as the introduction of a binding obligation to resort to

pacic means of dispute settlement – primarily arbitration – in positive international

law.

But, in the meantime, mainstream positivists preserved much of the old doc-

trine for the discipline of international law. In the end, the most fundamental differ-

ence between radical and mainstream positivists concerned the question what part

of the old jus ad bellum they considered to be part of international law. The radical

positivists drew the line at enforceable rights and obligations; mainstream positivists

also kept unenforceable rights and obligations corralledin.

The fusion of just and legal war expanded the scope of and for aggression. Whereas

under the dualist doctrine, an aggressive war was a war that was both unjust and

illegal and was an exceptional and aggravated violation of the law, aggression now

referred to any illegal war. This was a vague, indeterminate, but altogether wider

notion, and one to which international scholars increasingly referred when indicat-

ing a transgression of international use of force law. By this was meant any war that

was not fought in self-preservation or as an ultimate resort of dispute settlement, such

as wars for conquest or greed. The problem with it was that in most cases aggres-

sion could not be sanctioned as there was no objective platform from which to judge.

Nevertheless, a few authors did discuss the option of sanctions in case the illegality

of a war was manifest. Much in line with early modern doctrine, the suggestion was

Lynch, ‘Peace Movements, Civil Society, and the Development of International Law’, in Fassbender and

Peters, supra note 5, 198.

Bonls and Fauchille, supra note 88, at 577; Bulmerincq, supra note 88, at 357; Gardner, supra note

88, at 204–207; L.Levi, International Law, with Materials for a Code of International Law (1887), at 278;

Manning, supra note 84, at 96–97; G.F. Martens, supra note 88, at 452; Nys, supra note 89, vol. 3, at 106;

Ullmann, supra note 85, at 466; Woolsey, supra note 84, at 214.

Aggression before Versailles 797

made that in this case the suppression of the perpetrator became the concern of the

whole international community. Two sanctions were proposed: liability for the costs

and damages of the war and collective action to stop the offence and enforce guaran-

tees for future security.

If legal scholarship retained much of the old doctrine, nineteenth-century prac-

tice adhered even closer to tradition. Although the practice of formally declaring war

fell into disuse over the 19th century, the justication of force and war remained as

crucial to states as before. If anything, the growing impact of public opinion on for-

eign and national policy enhanced the need for governments to explain their actions

within and without the country. Since defensive alliance treaties were still an essen-

tial tool of security policy, and the right and duties of neutrals had expanded, foreign

governments continued to be a primary target audience. Whereas the forms of these

public communications grew ever more varied, the discourse used and its norma-

tive context did not evolve all that much. Manifestos and other public utterances that

served to legitimize war were couched in the language of just war all through the per-

iod under scrutiny. Their primary purpose was to deect the danger of being labelled

an aggressor.

By and large, justications were construed on the same basic line of argument as

before. They offered a list of offences that the enemy state had committed over a long

period of time and opposed its desire to harm one’s own desire for peace. The purpose

of this argumentative line was to indicate just cause and to persuade that one had done

everything possible to avoid war but that this now had become inevitable. Asurvey

of 19th-century practice shows three further trends. First, states referred to offences

against their honour and vital interests as a cause for war but preferably combined this

with violations of rights. Second, the relative weakening of the persuasive value that

came from the invocation of interest, including military necessity, was compensated

by a greater insistence that the enemy had been the rst to resort to violence. Third, if

one could neither invoke the violation of right or honour nor a prior armed action by

the enemy, the main road left was that of preventive self-defence. Justications of the

latter kind, like the one of King Frederick II in 1756, generally bespoke of an aware-

ness of the urgency not to be stained with the stigma of aggression.

100

Bello, supra note 88, at 151–152; Halleck, supra note 88, at 313–314; Kent, supra note 88, at 49; Saalfeld,

supra note 88, at 199; Woolsey, supra note 84, at 187–190.

Birkenhead, supra note 88, at 92; Bluntschli, supra note 88, at 293–294; Bonls and Fauchille, supra note

88, at 586–589; P.Bordwell, The Laws of War between Belligerents: AHistory and Commentary (1908), at

156–200; Funck-Brentano, supra note 88, at 241–245; Hall, supra note 88, at 315–322; Halleck, supra

note 88, at 351–356; Heffter, supra note 88, at 211; Hershey, supra note 83, at 356–359; Kent, supra note

88, at 52–55; Lawrence, supra note 85, at 299–302; Levi, supra note 97, at 281; Manning, supra note

84, at 118–120; G.F. Martens, supra note 88, at 453–454; J.F. Maurice, Hostilities without Declaration of

War from 1700 to 1870 (1883); Oppenheim, supra note 88, at 226; Phillimore, supra note 84, vol. 3, at

116–121; Rivier, supra note 88, vol. 2, at 221–222; Schmalz, supra note 89, at 221–222; Twiss, supra

note 84, vol. 2, at 56–80; T.A. Walker, The Science of International Law (1893), at 240–242; Wheaton,

supra note 88, at 313–315; Wilson, supra note 88, at 244–248; Woolsey, supra note 84, at 197–199.

100

Declaration of War by Russia against the Ottoman Empire, 26 April 1828, reprinted in British and Foreign

State Papers (BFSP) (1815–1977), vol. 15, at 656; Declaration of War by Uruguay against Argentina, 24

798 EJIL 29 (2018), 773–808

5 Aggression at Versailles

Aggression featured in the negotiations that led to the Versailles Peace Treaty in two

different contexts: the prosecution of the former German Emperor Wilhelm II and

reparations. The proposition to prosecute German leaders, including the emperor, for

having started a war of aggression and for transgressions against the laws and cus-

toms of war had been entertained on and off by British and French ofcials during the

war. It was part of the Allies’ wider plan to destroy Prussian autocracy and militarism

and construct a new world order on the basis of respect for international law.

101

1918, London and Paris made the prosecution of German war leaders into one of

their war goals. In the run up to the general elections of December 1918, the British

Prime Minister David Lloyd George (1863–1945) promoted the criminal prosecution

of the former emperor, now living in exile in the Netherlands, as a prominent item

of his campaign platform.

102

Notwithstanding strong hesitations about the wisdom,

feasibility and legality of such a move within his Cabinet, Lloyd George persisted.

103

a meeting in London on 2 December 1918, the three major European Allied leaders,

Lloyd George and his French and Italian counterparts Georges Clemenceau (1841–

1929) and Vittorio Orlando (1860–1952), agreed to pursue the idea at the peace

conference.

104

After its opening in Paris on 18 January 1919, the Inter-Allied Conference referred

the matter to the Commission on the Responsibility of the Authors of the War and

the Enforcement of Penalties (CRW). The commission, which counted several interna-

tional lawyers among its members – the American James Brown Scott (1866–1943),

the Frenchman Ferdinand Larnaude (1853–1945), the Belgian Edouard Rolin-

Jacquemyns (1863–1936) and the Greek Nikolaos Politis (1872–1942) – was chaired

by the US Secretary of State Robert Lansing (1864–1928), himself a erce opponent

February 1839, reprinted in 27 BFSP 1214; Declaration of War by the Ottoman Empire against Russia,

4 October 1853, reprinted in 42 BFSP 1321; Message of Queen Victoria to Both Houses on the Outbreak

of War with Russia, 27 March 1853, reprinted in 44 BFSP 110; Manifesto of War of Austria against

Sardinia, 28 April 1859, reprinted in 57 BFSP 228; Memorandum of Sardinia for the Invasion of the

Papal State, 12 September 1860, reprinted in 50 BFSP 358; Manifesto of War of Austria against Prussia,

17 June 1866, 63 BFSP 580; Manifesto of War of Prussia against Austria, 18 June 1866, reprinted in

63 BFSP 854; Declaration of War by France against Prussia, 19 July 1870, reprinted in Correspondence

Respecting the Negotiations Preliminary to the War between France and Prussia, 1870 (1870), at 9–10;

see also Recueil des documents relatifs aux origins de la guerre de 1870 (1910–1932), vol. 29; Decree of

China, Declaring War against Japan, 1 August 1894, reprinted in 86 BFSP 301; Proclamation of Japan,

Declaring War against China, 1 August 1894, reprinted in 86 BFSP 86.

101

Boemeke, ‘Woodrow Wilson’s Image of Germany, the War-Guilt Question, and the Treaty of Versailles’,

in M.F. Boemeke, G.D. Feldman and E.Glaser (eds), The Treaty of Versailles. AReassessment after 75 Years

(1998) 603; W.Mulligan, The Great War of Peace (2014); H.W.V. Temperley (ed.), A History of the Peace

Conference of Paris, 56 vols (1920), vol. 1, at 166.

102

J.F. Willis, Prologue to Nuremberg: The Politics and Diplomacy of Punishing War Criminals of the First World

War (1982), at 3–64.

103

Imperial War Cabinet 37, Minutes, London, le CAB/23/43, National Archives (NA). During this discus-

sion, numerous references were made to the fate of Napoleon after Waterloo.

104

Telegram, 2 December 1918, le FO 618/247, at 21, NA.

Aggression before Versailles 799

of the prosecution of the emperor. In its nal report, which was presented to the ple-

nary conference on 29 March 1919, the CRW ruled that Germany and its three allies,

Austria-Hungary, Turkey and Bulgaria, were responsible for planning and starting

the war. They stood morally condemned for it. According to the report, Germany and

Austria-Hungary had planned and premeditated the war in pursuance of a policy of

aggression. They had used the murder of the Habsburg heir to the throne, Archduke

Franz Ferdinand (1863–1914), by a Serbian nationalist in Sarajevo on 28 June 1914,

as a trigger and pretext for a war that Berlin had desired for some time. The CRW

claimed that the decision to go to war was taken at a conference in Potsdam on 5

July. After that, Germany had done everything it could to incite Vienna to resort to

war with Serbia and to derail Allied attempts at mediation, in the full knowledge that

an Austrian-Hungarian attack on Serbia might provoke Russia and lead to a Europe-

wide conagration.

105

In addition, Germany and Austria-Hungary were condemned

for violating the neutrality of Belgium and Luxemburg, which they had guaranteed by

treaty.

106

In its reservation to the report, the USA abetted the thesis of premeditation

by introducing a few more incriminating documents.

But if consent could be reached on indicating the Central Powers as aggressors, the

same could not be said about the question of criminal prosecution. In the end, the

USA as well as Japan rejected the report and made reservations. The American dele-

gates brought two major arguments to bear against the criminal prosecution of the

emperor: rst, the immunity of a head of state and, second, the lack of a law against

aggression at the time of its commission. In its reservation, the USA insisted on the

distinction between legal and moral offences.

107

On the latter point, the CRW con-

curred. The CRW rejected the argumentation of Larnaude and Albert de La Pradelle

(1871–1955), an international lawyer who was secretary-general of the CRW, to vest

the prosecution on the violation of the just war doctrine.

108

In a remarkable passage,

the commission ruled that the ‘premeditation of a war of aggression’ could not be

considered ‘an act directly contrary to positive law’. It based this statement on ‘the

purely optional character of the institutions at The Hague for the maintenance of

peace (International Commission of Inquiry, Mediation and Arbitration)’. Hereby, the

CRW referred to the Convention on the Pacic Settlement of International Disputes

of 29 July 1899, amended by the convention of 18 October 1899.

109

This convention

exhorted but did not oblige states to attempt pacic means of dispute settlement before

they resorted to war.

110

It only became an obligation which the report recognized as

legal through the Covenant of the League of Nations.

111

With this, the CRW adopted

105

Commission on the Responsibility of the Authors of the War and on Enforcement of Penalties

(Commission on Enforcement of Penalties), ‘Report’, 14 AJIL Suppl. (1920) 95, at 98–107.

106

Treaty of London 1839, 88 CTS 411, Art. 1; Treaty of London 1867, 135 CTS 1, Art. 2; Commission on

Enforcement of Penalties, supra note 105, at 107–112.

107

‘Memorandum of Reservation Presented by the Representatives of the United States to the Report of the

Commission on Responsibilities’, 14 AJIL Suppl. (1920) 127, at 128.

108

F. Larnaude and A.de La Pradelle, Examen de la responsabilité pénale de l’Empereur Guillaume II (1918).

109

Hague Convention for the Pacic Settlement of International Disputes 1899, 1 AJIL 103 (1907).

110

Ibid., Art.1.

111

Ibid., Arts 12–15.

800 EJIL 29 (2018), 773–808

the restricted denition of international law as positive, enforceable rules. In order to

escape the contentious issue of criminal prosecution while saving the politically all

important moral condemnation of Germany as aggressor, it chose to align itself with

the previously radical positivist minority and demote early modern and 19th-century

legal doctrine to a matter of ‘public conscience’.

112

The assertions that the Central Powers did not violate any existing law through

their aggression and that aggression did not constitute an injury were all the more

astonishing as they were unnecessary to attain the goal of preventing a criminal pros-

ecution of Emperor Wilhelm II. It would have sufced to state that aggression was not

an individually imputable crime and invoke the principle of non-retroactivity from

domestic law by analogy. It went a step further – to sustain the analogy with domestic

law – by also denying that it constituted a civil delict at the time. Part of the explana-

tion for this somewhat odd choice came from James Brown Scott’s erce, but not very

sophisticated, opposition against Larnaude’s appeal to the discriminatory logic of just

war.

113

This legal strategy becomes even more peculiar if one considers that the CRW pos-

itively afrmed that Germany and Austria-Hungary had violated international law

with regard to the neutrality of Belgium and Luxemburg. Nevertheless, the commis-

sion likewise counselled against the prosecution of the former emperor for this afrm-

ation. It did not offer any reason for this, but from the relevant section in the report,

it can be inferred that this advice was based on the principle of the non-retroactivity

of criminal offences. The report underscored the point that aggression and the viola-

tion of treaties were not individually imputable crimes through its statement that they

should be made so in the future.

114

The report did not satisfy the British and French political leadership, which contin-

ued to insist with the American President Woodrow Wilson (1856–1924) on the pros-

ecution of the former emperor. In early April, Wilson and Lloyd George, who direly

needed to deliver on his campaign promise, reached an agreement. Wilson drafted a

clause that became almost literally Article 227 of the Versailles Peace Treaty. The idea

to prosecute the emperor for a crime was relinquished. Instead, he would be ‘arraigned

for a supreme offence against international morality and the sanctity of treaties’. The

former emperor would be brought before, and possibly punished by, a tribunal of rep-

resentatives of the ve Allied great powers, which would be ‘guided by the highest

motives of international policy, with a view to vindicating the solemn obligations of

international undertakings and the validity of international morality’. Whereas the

guarantee of the neutrality of Belgium and Luxemburg was caught under the term

‘undertaking’, ‘international morality’ pointed at aggression. The underlying legal

112

Commission on Enforcement of Penalties, supra note 105, at 118.

113

Willis, supra note 102, at 72–73; see also Scott, ‘The Trial of the Kaiser’, in E.M. House and C.Seymour

(eds), What Really Happened in Paris: The Story of the Peace Conference, 1918–1919 by the American

Delegates (1921) 231.

114

Commission on Enforcement of Penalties, supra note 105, at 119–120.

Aggression before Versailles 801

reasoning of the CRW’s report does not seem to have played a role in the principals’

wheeling and dealing.

115

The agreement was not much of a compromise but, rather, constituted a major

concession on the part of Wilson who needed to buy British and French indulgence on

some unrelated matters. Whereas Wilson attained his goal that the former emperor

would not truly be brought before an international criminal tribunal, Lloyd George

and Clemenceau could claim they had managed to have Emperor Wilhelm II brought

to justice. Even if, for lawyers, it was far from clear what this really involved, the moral

condemnation of Germany’s aggression and the idea that the emperor might not

escape the consequences of his actions stuck in the publiceye.

But, whatever its political signicance, it was a legal conundrum. The deal came at

the price of extreme legal ambiguity, if not outright inconsistency. By labelling aggres-

sion a matter of international morality and not naming it a criminal prosecution, it

avoided the pitfall of breaking the general principle of non-retroactivity. But, by call-

ing for a punishment, it revived that danger. Even if one read the article to mean that

punishment could only apply for the violation of treaties, which was evidently consid-

ered an injury against existing international law at the time of its commission, retro-

activity reared its head again. Just like aggression, this had not been an individually

imputable criminal offence in 1914.

116

Next to the prosecution of enemy leaders, reparation also gured high on the agenda

of France and Britain for a just peace settlement. From the moment negotiations with

Germany started about an armistice in October 1918, it became a point of tension

between the European Allies and the USA. On 6 October 1918, Germany requested an

armistice from the Allied and Associated powers in a note delivered through the good

ofces of the Swiss government to President Wilson. The note proposed that peace

negotiations would be started on the basis of the conditions that Wilson had set out in

his Fourteen Points speech of 8 January 1918 and in his subsequent speeches.

117

The

Allied acceptance of the German proposal to take Wilson’s expression of Allied war

aims as binding preliminaries to a future peace treaty framed the debate on repara-

tions from the start. It meant that indemnities were excluded.

Since the Napoleonic era, many peace treaties had stipulated indemnities. These

were lump sum payments imposed upon the loser of a war in compensation for the

costs and damages the victor had suffered. These payments were not based on any

allegation of wrongdoing but, rather, on the simple fact of defeat. They did not involve

an attribution of guilt or violation of the law, neither at the level of jus ad bellum nor

jus in bello. Consequently, they did not detract from the logic of legal war.

118

Wilsons’s

115

L. Smith, Sovereignty at the Paris Peace Conference of 1919 (2018), at 79–80; Willis, supra note 102, at 81.

116

Ibid., at 77–81.

117

Note of Max van Baden to W.Wilson, 6 October 1918, reprinted in Foreign Relations of the United States

(FRUS), Supplement no.1: The World War (1918), at 338.

118

L. Camuzet, L’indemnité de guerre en droit international (1928), at 41–79; Tomuschat, ‘The 1871 Peace

Treaty between France and Germany and the 1919 Peace Treaty of Versailles’, in R.Lesaffer (ed.), Peace

Treaties and International Law in European History: From the End of the Middle Ages to World War One (2004)

382.

802 EJIL 29 (2018), 773–808

approach to peace excluded the option of indemnities. This did not put the Allies before

insurmountable problems as the European Allies had been couching their nancial

demands in the language of justice long before the end of the war. They desired com-

pensation for all losses that were caused by the Central Powers’ illegal actions. The

question remained, however, to what losses this extended in practice? From the start

of the pre-armistice negotiations, this question led to erce altercations between the

USA and its main European Allies. The pre-armistice agreement reached among the

Allies and with Germany would frame the discussion all through the peace nego-

tiations. The agreement to base the peace settlement on Wilson’s speeches and the

exchange of notes between the USA, acting on behalf of the Allied and Associated

powers, and Germany came to be seen as a pactum de contrahendo, as binding peace

preliminaries. Henceforth, the inter-Allied, as well as the Allied-German, debate on

reparations would be one about the extent of Germany’s pre-armistice, contractual

obligation to pay compensation.

Of Wilsons’s Fourteen Points, three related to reparation. Point 7 called for Belgium

to be evacuated and ‘restored’. Point 8 mentioned that the ‘invaded portions’ of

France had to be ‘restored’. Point 11 used the same term for the ‘occupied territories’

of Romania, Serbia and Montenegro.

119

In the opinion of the US legal advisers, this

limited reparations to the damage caused by violations of international law in these

occupied territories, with the exception of Belgium where it was extended to all costs

and damages the country had suffered in consequence of the war. This was based on

the assertion that the invasion of Belgium was contrary to international law as it vio-

lated Germany’s treaty guarantee of Belgian neutrality.

120

During the pre-armistice

negotiations, the USA expanded this to cover all damages pertaining to the northeast-

ern provinces of France, which the German army had reached by cutting through

Belgium.

121

From the start of the American–German negotiations, the European Allies were

worried that founding the peace settlement on the Fourteen Points would curtail

their desire for reparations. ABritish memorandum of 12 October expressed the fear

that the Fourteen Points would be interpreted in such a way as to only cover damage

to civilian property and exclude damage to civilian persons. Moreover, it seemed to

exclude damage resulting from the illegal actions of the Central Powers on the seas

against Allied and neutral shipping.

122

The altercations between France, Britain and

the USA of October and early November 1918 centred on these two points. The end

result was a reservation of the Allied governments to the Fourteen Points. In the res-

ervation, they stressed that the Fourteen Points implied that ‘compensation [would]

119

Address of W.Wilson to Congress, 8 January 1918, reprinted in FRUS, Supplement no.1: The World War

(1918), at 12.

120

Miller, ‘The American Program and International Law, Extracts’, in P.M. Burnett (ed.), Reparation at the

Paris Peace Conference: From the Standpoint of the American Delegation, 2 vols (1940), vol. 1, at 363.

121

American Commentary on the Fourteen Points, Extracts, in Burnett, supra note 120, vol. 1, at 386;

Memorandum of the Advisory Council of the American Mission to the Inter-Allied Council, 12 December

1918, reprinted in FRUS, Paris Peace Conference (1919), vol. 2, at 584.

122

Burnett, supra note 120, at 382.

Aggression before Versailles 803

be made by Germany for all damage done to the civilian population of the Allies and

their property by the aggression of Germany by land, by sea and from the air’. In his

note of 5 November, by which the USA accepted the German proposal for an armi-

stice, Lansing included this reservation and afrmed that it carried the endorsement

of Wilson. Thereby, it became part of the pactum de contrahendo.

123

The reference to aggression had only been slipped into the nal version of the res-

ervation. It replaced the phrase ‘by the invasion’, which in turn had superseded the

original ‘by the forces’. The change was made in order to include damage following

from the maritime war.

124

It did not imply an open assertion on the parts of the Allies

nor an admission on the part of Germany that the war itself was illegal on the German

side and that Germany was liable for all war costs and damages. But, nevertheless, its

inclusion opened the door to that interpretation.

After the opening of the conference in Paris, a Commission on the Reparation of

Damages (CRD) was established. The French Minister of Finance Louis-Lucien Klotz

(1868–1930) became its chairman. From the inception of its real activities in February,

the CRD became the grounds of a clash between France and Britain, on the one hand,

and the USA, on the other hand, over the width and breadth of Germany’s obligation

to pay reparations. During November and December 1918, politicians, lawyers and

opinion makers of different ilk in both European countries had stoked the re for the

demand of ‘full reparation’. In practice, this meant the inclusion of military war costs

next to personal and property damage. Several legal arguments were forwarded to base

this on while remaining within the connes of the pre-armistice agreement. But, under

these, lurked the assertion that Germany had acted illegally in starting the war and

committing aggression and was henceforth liable for all ensuing costs and damages.

125

The CRD proved unable to solve the question on its own in a denite way. The dis-

cussions went back and forth between the Council of Four, the Council of Ten, the

CRD and the delegations’ legal experts. The end result were Articles 231 and 232 of

the Versailles Peace Treaty, on which the political leadership reached agreement in

April. This time, the deal was largely crafted and drafted by both Wilson and Lloyd

George. The nal text had gone through many revisions. It was remotely based on a

draft made by John Foster Dulles (1888–1959), who served on the American delega-

tion as legal counsel.

126

The crux of the compromise was a dual proposition to assert

the liability of Germany for full reparations but to factually limit those and exclude

war costs – except those of Belgium.

127

Articles 231 and 232, which resulted from

the discussions among the Allies, were closely connected. Article 231 stated the theo-

retical responsibility of Germany for ‘causing all the loss and damages to which the

123

FRUS, Supplement no.1: The World War (1918), at 468; see also Temperley, supra note 101, vol. 1, at

373; Smith, supra note 115, at 67–69.

124

Telegram from E.House to W.Wilson, 4 November 1918, reprinted in FRUS, Supplement no.1: The

World War (1918), at 460; Dickmann, supra note 12, at 46.

125

Burnett, supra note 120, vol. 1, at 9–16.

126

First Dulles draft, 21 February 1919, reprinted in Burnett, supra note 120, vol. 1, at 600.

127

Council of Four, Meeting of 30 March, 5 April, 5 April 1919, reprinted in FRUS, Paris Peace Conference

(1919), vol. 5, at 15, 21, 31; Council of Ten, Meeting of 1 March 1919, reprinted in ibid., vol. 4, at 173;

Burnett, supra note 120, vol. 1, at 17–31, 66–70; Lamont, ‘Reparations’, in House and Seymour, supra

note 113, 259.

804 EJIL 29 (2018), 773–808

Allied and Associated Governments and their subjects [had] been subjected as a con-

sequence of the war imposed upon them by the aggression of Germany and her allies’.

Article 232 limited Germany’s actual obligation to the compensation of all damage

done to civilians and their property and of all Belgian damage and war costs. For the

prior point, Article 232 repeated the language of the 5 November reservation by quot-

ing the words ‘by such aggression by land, by sea and from the air’. For the latter point,

it asserted Germany’s prior agreement to give Belgium full compensation.

In later years, an extensive political as well as academic debate would break loose

about the question whether Article 231 did imply a moral condemnation of Germany.

This referred to the question whether Germany’s aggression constituted a moral out-

rage, which also should be considered a crime even if it was not at the time of its

commission. It was a question that not only divided Germany from the Allies but also

remained a major point of contention among statesmen, diplomats and academics

within the Allied world. In one of the best documented studies from the interwar per-

iod, the French historians Marc Bloch (1886–1944) and Pierre Renouvin (1893–

1974) argued that Article 231 had not been intended as a war guilt clause but, rather,

as an assertion, albeit a merely theoretical one, upon which to base Germany’s liability

for full reparation. In legal terms, this meant that aggression constituted an injury in

analogy to a civil law delict rather than a crime.

128

These were indeed the terms under which the debate about what Articles 231

and 232 implied was waged. But this left open the question what ‘aggression’ itself

referred to. Did it only refer to some concrete violations of international law, such as

the invasion of Belgium and breaches against the laws and customs of war, or did it

imply the full illegality of the war on Germany’s part? The truth is that the statesmen

who drafted these articles did not make any conscious decision on the matter.

129

But

the logic of the case dictates that a statement of Germany’s liability for full reparation

– ‘all the loss and damages’, however circumspect – could hardly mean anything but

an assertion that Germany had acted illegally by starting the war and invading and

that all of its war actions were, by consequence, illegal. This opened an incongruence

between the outcome of the debate on the prosecution of the former emperor and that

on reparations. Whereas the CRW stated that aggression had not constituted a viola-

tion of international law in 1914, Article 231 made the opposite assertion.

But, whatever the conscious intentions, or lack thereof, of the Allies were at the

time of the drafting of the Versailles Peace Treaty, it is an irony of history that it was

the German reaction to the text of the treaty that settled the debate to Germany’s dis-

advantage. On 7 May 1919, the German delegation was presented with the draft of

the Versailles Peace Treaty. The Germans were not given a copy of the CRW report on

128

Bloch and Renouvin, ‘L’Art. 231 du traité de Versailles: sa génèse et signication’, 10 Revue d’histoire de la

guerre modiale (1932) 1; see also Binkley and Mahr, ‘A New Interpretation of the Responsibility Clause in

the Versailles Treaty’, 24 Current History (1929) 398; Binkley, ‘The Guilt Clause in the Versailles Treaty’,

30 Current History (1929) 294.

129

Burnett, supra note 120, vol. 1, at 156–157.

Aggression before Versailles 805

war responsibility but knew its content anyway.

130

Nevertheless, the German delega-

tion responded to the CRW report through a memorandum signed by four prominent

academics, among who were Max Weber (1864–1920) and Hans Delbrück (1848–

1929), but which was largely prepared by an ofcial of the Foreign Ministry.

131

29 May, one day after the submission of that memorandum, by which the German

delegation had acted against the orders of the Cabinet in Berlin, the delegation pre-

sented its extensive reply to the Versailles Peace Treaty text.

132

Wrongly assuming

that Article 231 was based on the CRW report, it thought that the article included a

clear assertion that Germany and its allies were found guilty of aggression and stood

condemned for an offence against international morality. Germany’s staunch denial

and attack on the iniquity of the Allies, which had made this assertion after having

rejected Germany’s proposal of November 1918 for a commission of inquiry staffed

by representatives from neutral countries, elicited a virulent reply by the Allies.

133

their reaction of 16 June, the Allies left no doubt that the peace treaty was meant to

condemn Germany for being the aggressor and that this was to be considered a crime.

It unequivocally stated that the treaty ‘intended to mark a departure for the traditions

and practices of earlier settlements which have been singularly inadequate in prevent-

ing the renewal of war’.

134

Although these and similar assertions were made with

regard to Article 227 rather than Article 231, the whole thrust of both the German

defence and the Allies’ altercation was to promote the condemnation for aggression as

one of the foundational stones under the entire peace settlement.

Germany’s defence harked back to the pre-armistice agreement, on the basis of

which it tried to minimize its obligation to pay reparations. But the core of its defence

against the CRW report, Articles 227 and 231–2 was not so much the assertion that

aggression was not a violation of international law nor an individually imputable

crime but, rather, that Germany had not committed aggression. Thereby, even if it

assumed it was defending itself against the accusation of having committed a moral

offence, it still implied that aggression had not been considered acceptable in 1914.

But, whatever their position on the scope of international law at the time of the con-

ference was, the very least that can be concluded is that Germany knew what it was

accused of under ‘aggression’ and referred to a tradition that had marked aggression

as a violation of the use of force law. This conclusion is corroborated by the fact that

130

Reply to the Principal German Representative, 20 May 1919, reprinted in FRUS, Paris Peace Conference

(1919), vol. 5, at 742.

131

Bernhard Wilhelm von Bülow (1885–1936). Observations of the German Delegation on the Report of

the Commission of the Allied and Associated Governments as to the Responsibility of the Authors of the

War, reprinted in FRUS, Paris Peace Conference (1919), vol 6, at 781. See Dickmann, supra note 12, at

86–89; Herwig, supra note 12, at 93–94.

132

Observations of the German Delegation on the Condition of Peace, reprinted in FRUS, Paris Peace

Conference (1919), vol. 6, at 795.

133

Krüger, supra note 12, at 44–47.

134

Reply of the Allied and Associated Powers to the Observations of the German Delegation on the Conditions

of Peace, 16 June 1919, reprinted in FRUS, Paris Peace Conference (1919), vol. 6, at 926, at 961–962.

806 EJIL 29 (2018), 773–808

Germany’s defence against the accusation of aggression from 1919 was essentially

similar to its justication for war in1914.

When Germany declared war on Russia and France and invaded Luxemburg and

Belgium in August 1914, it did not publish a single, comprehensive text to justify its

decisions. But a general line of justication can be inferred from different texts. These

include Germany’s ultimatum and declaration of war to Russia, its declaration of

war to France, its ultimatum to Belgium, the speech of its Chancellor Theobald von

Bethmann Hollweg (1856–1921) in the Imperial Diet of 4 August and the German

White Book with diplomatic correspondence, which was released shortly after the

commencement of the war.

135

Both in 1914 and 1919, Germany construed the jus-

tication of its actions of August 1914 on two separate arguments. Its major con-

cern was to deect the blame for the Europe-wide escalation of the bilateral conict

between the Habsburg monarchy and Serbia after the assassination of the archduke.

First, since Germany neither could nor wanted to deny that it had supported Vienna’s

desire for retribution and security guarantees from Serbia, even at the cost of war, it

consistently argued that Austria-Hungary had a just cause of war and, as its ally, it

had a right and interest to support it. The German defence implied that the assassi-

nation of the archduke constituted an injury. Moreover, the event was just another

proof of Serbia’s continuous attempts to harm Austria-Hungary and, in collusion

with Russia, to destroy it as a great power. As it was a vital interest for Germany that

Austria-Hungary retained its status as a great power and as Germany was treaty-

bound to an alliance with Vienna, Germany had no basis to stop Vienna’s search for

retribution. However, it had counselled moderation.

Second, Germany could not be held responsible for the escalation of the Austrian-

Serbian war into a European war. On the contrary, it had done everything to keep it an

isolated, bilateral conict. Whereas Germany stood accused of having pushed Vienna

to war in the full knowledge and hope that this could provoke Russia to protect Serbia

and trigger the series of alliance treaties bringing at least Russia, Germany and France

into the war, it argued that the opposite was true. It threw the accusation back at

Russia, which, according to Germany, had been plotting war against Austria-Hungary

and the Ottoman Empire for years in the hope of securing access to the Mediterranean.

It indicated Russia’s decision for full mobilization at the end of July 1914 at a time

when Germany was, at the instigation of Britain, trying to mediate between Saint

135

Telegram of Bethmann Hollweg to the German Minister in Brussels, 2 August 1914, The German White

Book: The English Translation Issued by the German Government August 1914 (1914), reprinted in J.B.

Scott (ed.), Diplomatic Documents Relating to the Outbreak of the European War (1916), vol. 2, at 769, 813;

German Ultimatum to Belgium, 3 August 1914, reprinted in G.P. Gooch and Harold Temperley (eds),

British Documents on the Origins of War 1898–1914 (1926), vol. 11, at 340; German Declaration of

War against France, 3 August 1914, reprinted in K. Kautsky, M.Montgelas and W.Schücking (eds),

Die deutschen Dokumenten zum Kriegsausbruch (1919), vol. 3, at 187; Address of Bethmann Hollweg to

Imperial Diet, 4 August 1914, reprinted in Stenographische Berichte über die Verhandlungen des Reichstags,

Dienstag 4 August 1914. Leg XIII.2 (1914), vol. 306, at 5; Telegram of Bethmann Hollweg to German

Ambassador at Saint-Petersburg, 31 July 1914 and 1 August 1914, The German White Book, reprinted in

Scott, ibid., vol. 2, at 46, 47.

Aggression before Versailles 807

Petersburg and Vienna as the true cause for the war. After Russia ignored Germany’s

ultimatum of 31 July to cease its military preparations, Germany was left with no

choice but to declare war on Russia and France and invade Belgium and Luxemburg.

This was founded on military necessity and the certainty that France would stand by

its ally Russia. Under prevailing German doctrine, Germany could only hope to win a

two-front war against Russia, France and possibly Britain if it could take advantage of

its capacity to mobilize faster than Russia and take out France before Russia was fully

prepared for war. For this, it needed to bypass French defences at the German border by

cutting through Luxemburg and Belgium. According to Germany, Russia’s decision to

mobilize and to continue its preparations in the face of the German ultimatum made

it the true aggressor. Germany’s justication of 1914 and 1919 showed great similar-

ity to King Frederick II’s justication in 1756. In both cases, they pleaded preventive

defence on the basis of a combination of certainty that the enemy would attack in

the near future and of necessity built on an assessment of the military situation and

their own operational doctrine and policies.

136

The invocation by Germany of its own

military doctrine severely weakened the whole argument.

137

The 1914 justication was beefed up with false accusations of military incur-

sions in Germany and the use of Belgian airspace by the French prior to the German

declaration of war. In his speech to the Diet, Bethmann Hollweg conceded explic-

itly that the invasion of Belgium and Luxemburg constituted violations of German

treaty obligations and that Germany was going to compensate for the damages later.

It was justied, however, by the necessity to defend the fatherland. Both statements

were part of the chancellor’s strategy to secure the support of the socialist party, the

Sozialdemokratische Partei Deutschlands, in the German parliament, for which only

a defensive war was acceptable.

138

The rst statement also served the agenda of trying

to trigger the defensive alliance Vienna and Berlin had with Italy.

139

Both statements

were retracted in subsequent months.

140

6 Conclusion

If the parties to the Versailles Peace Treaty could agree on one thing, it was that the

treaty radically departed from long-existing practice. The return to a discriminatory

conception of war, the attribution of guilt, the enactment of reparations on the basis

136

C. Clark, The Sleepwalkers: How Europe Went to War in 1914 (2013); W.Mulligan, The Origins of the First

World War (2010), at 93–96; T.G. Otte, July Crisis: The World’s Descent into War, Summer 1914 (2014).

137

De Visscher, ‘Les lois de la guerre et la théorie de la nécessité’, 24 Revue Générale de Droit International

Public (1917), 94; J.W. Garner, International Law and the World War (1920), vol. 2, 186–237.

138

Mulligan, supra note 101, at 72.

139

Treaty of Alliance of Vienna between Austria-Hungary, Germany, and Italy 1912, 217 CTS 311; Foreign

Secretary to British Ambassador at Paris, 2 August 1914, British Blue Book 1, reprinted in Scott, supra

note 135, vol. 2, 861, at 1002; Italian Green Book, reprinted in Scott, ibid., vol. 2, 1207, especially the

Telegram of Foreign Minister to Italian Ambassador in Vienna, 9 December 1914, at 1209.

140

German White Book, reprinted in Scott, supra note 135, vol. 1, at 815, 837.

808 EJIL 29 (2018), 773–808

of justice and the prosecution of German war leaders all broke with centuries of peace

treaty practice. But the conception of aggression as a violation of the rules that regu-

lated resort to war was not new; it drew on a long-standing tradition that had its roots

in the dualist logic of just and legal war from early modern Europe and that had sur-

vived within the lore and practice of international law. The originality of Versailles lay

in actually rendering a verdict on who the aggressors were and in sanctioning them,

not in inventing the concept.

But, if the drafters of the Versailles Peace Treaty made history, they also started to

rewrite it. The most elaborate debate on war guilt and aggression during the Inter-

Allied Conference of January to May 1919 at Paris took place within the CRW. In its

report, the commission condemned Germany for having planned and started a war

of aggression, clearly asserting that this had been an offence in 1914 and had been

understood to be so. But, in a move that was as astonishing as it was unnecessary, it

immediately added that the offence had not been one against international law but,

rather, a moral one. In order to do so, it reduced international law to, rst, positive law

and, second, enforceable rights and obligations, thus assuming the position on use of

force law of the small minority of radical positivists such as Westlake and Oppenheim.

The position was inconsistent with the conclusion the Allies reached on the repa-

rations debate. Here, the product of their deliberations was an assertion, albeit an

unconscious one, that aggression had been a violation of enforceable international

law in 1914. But to the statesmen, diplomats and the wider audience in 1919, and

in the ensuing ght over the legitimacy of Versailles, this was all juridical hair split-

ting. Whatever the Allied authors of the Versailles Peace Treaty had meant when they

wrote the text, by the time the treaty was signed on 28 June 1919 they had moved to

a ringing condemnation of German aggression, a supreme offence against interna-

tional morality. With this, they, as much as the German detractors of Versailles, did

rewrite the history of international law.