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Peace Treaties after World War I

Randall Lesaffer, Mieke van der Linden

Peace treaties — Armed conflict — World War I to World War II — Conduct of hostilities — Prisoners of war — Belligerence
Published under the auspices of the Max Planck Institute for Comparative Public Law and International Law under the direction of Rüdiger Wolfrum.

A.  Historical Background

Before the late 18th century, it was customary for multilateral peace conferences to result in a set of bilateral peace treaties. This started to change by the 18th century as peace conferences were increasingly concluded with a multilateral peace treaty. World War I, however, was not concluded with one comprehensive or ‘universal’ peace treaty, nor was it possible to settle the war at one single peace conference. The first explanation for this is that Russia, after the Bolshevik Revolution of November 1917, made a separate peace with the Central Powers (Brest-Litovsk, Peace of [1918]). The second explanation is that, although the Allied and Associated Powers, as the Western victors of the war and their non-Western Allies styled themselves, preferred to act as one towards the Central Powers, they chose to split up the Central coalition and make a separate peace treaty with each of their enemies.

A number of different peace treaties thus ended World War I. These can be catalogued in five groups. First, there are the peace treaties of 1918 between the Central Powers and the new Bolshevik regime in Russia that sealed the victory of Germany in the East. The treaties also involved Finland, the three Baltic States—Estonia, Latvia, and Lithuania—as well as Ukraine and Georgia, which—temporarily in the case of the two latter States—gained their independence from Russia, as well as Romania. Second, the Allied and Associated Powers, led by France, Great Britain, and the United States, on the one side concluded five peace treaties at the Paris Peace Conference in 1919 and 1920 with each of the Central Powers on the other side. These included the Versailles Peace Treaty (1919) with Germany, the St Germain Peace Treaty (1919) with Austria, the Neuilly Peace Treaty (1919) with Bulgaria, the Trianon Peace Treaty (1920) with Hungary, and the Sèvres Peace Treaty with the Ottoman Empire (1920) (the ‘Paris Peace Treaties’). The latter was, however, never ratified. The three other groups came out of the abrogation or failure of some of these first-mentioned treaties. Third, Art. 116 Versailles Peace Treaty forced the Central Powers to abrogate the advantageous peace treaties they had made for the Eastern European theatre in 1918. This meant, among others, that the state of war between Germany and Soviet Russia remained unsettled after 1919. Relations between the two powers were normalized by the Rapallo Treaty (1922). Meanwhile, the Soviets had gained the upper hand in the civil war and made peace in 1920 and 1921 with five States that had seceded from the former Russian Empire, namely Finland, Estonia, Latvia, Lithuania, and Poland. Ukraine lost its independence. Fourth, the Sèvres Treaty, which dismantled the Ottoman Empire and left the Turks with a small rump State, was highly controversial from the start. The victory of the nationalist movement under Mustafa Kemal, later known as Atatürk (1881–1938) over the regime of the last Sultan, Mehmet VI (1918–22), and Kemal’s successful fight against the Allied occupants and the Greeks, sealed the fate of the treaty. In 1923, Mustafa Kemal succeeded in obtaining a far better agreement than Sèvres with the Lausanne Peace Treaty (1923). Fifth, the refusal of the United States Senate to ratify the treaties that came out of the Paris Peace Conference left the state of war with the Central Powers unsettled. In 1921, the United States made separate peace agreements with Germany, Austria, and Hungary.

B.  Peace Treaties

1.  Central Powers’ Treaties in the East (1918)

After coming to power in November 1917, the Bolsheviks sued for peace. The Central Powers made an armistice with Soviet Russia on 15 December 1917, which allowed peace negotiations to start as of 22 December 1917. Peace negotiations were interrupted by the Soviets after a Ukrainian delegation had been admitted to the conference.

On 9 February 1918, the Central Powers made peace with the newly independent Republic of Ukraine. The treaty confirmed the Western border of the new State where the borderline had existed before between Austria-Hungary and Russia. The parties waived any claims for indemnification or compensation for damages and costs of the war. In an additional treaty, Ukraine accepted the obligation to deliver yearly a certain amount of grain to the Central Powers. The country remained effectively occupied by the Central Powers throughout the remainder of the war.

After having abrogated the armistice on 16 February 1918, the Germans renewed their offensive against Russia. This forced the Soviets back to the negotiation table. The harsh German ultimatum of 22 February 1918 was accepted by the Soviets two days later. On 3 March 1918 peace was concluded at Brest-Litovsk between the four Central Powers and Russia. On 27 August 1918, the treaty was supplemented with another treaty made at Brest-Litovsk that imposed a compensation of 6 million gold marks upon Russia and forced it to recognize the independence of Georgia. Due to the armistice of 11 November 1918 and the Paris Peace Treaties, the Central Powers had to abrogate the Brest-Litovsk Peace Treaties.

Finland had declared its independence from Russia on 6 December 1917. On 1 March 1918, Finland made its peace with Germany in the Berlin Peace Treaty. Apart from a general peace clause, the treaty also included a waiver for all war costs, but provided for compensation for the damages suffered by civilians. It also stipulated the restoration of all private rights and the restitution of confiscated merchant ships and their cargoes. Finland also concluded the Vienna Peace Treaty, together with an additional economic treaty, with Austria-Hungary on 29 May 1918. This provided for the mutual waiver of all compensations.

Romania made peace with the Central Powers at Bucharest on 7 May 1918. Romania had found itself largely under occupation by the Central Powers by the end of 1916. On 9 December 1917, an armistice had been signed at Foksani, followed by a preliminary peace at Buftea on 5 March 1918. Under the final peace treaty of 7 May, Romania had to cede the southern Dobruja to Bulgaria and lost some border land to Hungary. Northern Dobruja would continue to be administered by the Central Powers, although Romania was allowed access to the Black Sea. On 11 April 1918, the Central Powers allowed Romania to annex Bessarabian Kishinev in Moldova, which it had taken from Russia. The exploitation of Romanian oil resources was granted to a company which stood under German control. The Bucharest Peace Treaty made Romania into little more than a German-Austrian satellite.

The three Baltic States had been largely under German occupation since 1916. Lithuania declared independence on 16 February 1918, but its aspirations as those of the nationalist movements in two other Baltic territories were cut short by an assembly which was dominated by the German population of the area. On 8 March 1918, the assembly founded the Duchy of Courland and offered it to Emperor Wilhelm II (1888–1918). The Emperor became ruler of a new monarchy spanning the three Baltic regions on 14 April 1918.

The successful if temporary conclusion of the war in the East by the Central Powers was followed by their collapse against the Western powers by the autumn of 1918. The Central Powers were forced to seek armistices from the Western powers. Bulgaria concluded an armistice at Prilep on 29 September 1918, followed by the Ottoman Empire at Mudros on 30 October 1918, Austria-Hungary at Villa Giusti on 3 November 1918, Germany at Compiègne on 11 November 1918, and Hungary—separately this time—at Belgrade on 13 November 1918. The five armistices provided for the abrogation of the treaties signed with Russia or any State that had been formed on former Russian territories after the inception of war.

2.  Allied Peace Treaties with Central Powers (1919–20)

10  The Paris Peace Conference resulted in five peace treaties between the Allied and Associated Powers and the Central Powers separately in 1919 and 1920 (see para. 2 above). The Paris Conference opened on 18 January 1918 with the representatives of 27 Allied and Associated Powers present. The five defeated powers were not yet invited to the negotiation table. To the belligerent Allied Powers, Poland and Czechoslovakia, which had gained their independence in the final months of the war, had been added, as were the representatives from the Hedjaz, the Arab allies of the British who had helped them bring down the Ottomans. A Serb-Croat-Slovene delegation represented the new State that had been formed by Serbia, Montenegro as well as the former Habsburg provinces of Slovenia, Croatia, and Bosnia-Herzegovina. The British were joined by delegations from Australia, Canada, New Zealand, South Africa, and India, which brought the number of delegations on the Allied side up to 32. Soviet Russia and the other States that had emerged from the former Russian Empire were not represented at the conference.

11  The principal body of the conference was the Council of Ten. Although there were commissions, the Plenary Conference fulfilled only a formal role. Representatives of smaller countries and claimants, including the Yugoslavs, Hedjaz, the Zionists, the Druses, and the Armenians, appeared before the Council of Ten. During the first five months of the conference, in which the focus of the Great Powers was on reaching an agreement over and with Germany, Germany was not invited at any stage of the negotiations. Some of the main leaders were personally present during part of the Conference, including the American President Woodrow Wilson (1856–1924), the British Prime Minister David Lloyd George (1863–1945), and the French Prime Minister Georges Clemenceau (1841–1929). An unequalled and difficult negotiation process followed. The main aims of the British delegates to the conference were the assurance of French security, the removal of the threat of the German High Seas Fleet, the settlement of territorial questions, and the foundation of the League of Nations. The French delegation, under the direction of Clemenceau, aimed to weaken the German military forces in a strategic and economic way. Clemenceau tried to coerce the American and British delegations to guarantee French security in the event of another German attack. As a result, Wilson was confronted with rival and conflicting claims and purposes at the conference. He tried to align Britain and France, and attempted to gain support for and acceptance of the establishment of the League of Nations, as part of the Paris Peace Treaties, and his Fourteen Points Programme, in which democracy, sovereignty, liberty, and self-determination were advocated. In his Fourteen Points and some important speeches of 1918, Wilson had suggested the rehabilitation of Germany and the importance of its participation in the new world order; Germany had to become a member of the League of Nations. France and Britain, however, received the Fourteen Points of Wilson (1918) with great reluctance and even refused to adopt some of its core principles and specific provisions, especially those on the right to self-determination. In return, France and Britain appeased Wilson by giving their consent to the establishment of the League of Nations, which was instituted in order to regulate violence and the use of force, and was occupied with the right to self-determination and with minority rights (see para. 37 below). In the end, the United States neither ratified the Versailles Peace Treaty nor joined the League of Nations, because of an isolationist sentiment in the United States and alleged dissonance between the American Constitution and several provisions in the Versailles Peace Treaty. The Congress feared losing control over foreign affairs and the increase of presidential power vis-à-vis the Congress.

12  Under the yoke of nationalism and the protection of national interests, the Paris Peace Conference diverted from the practices of previous great peace conferences in that the victorious and defeated powers did not enjoy an equal position at the conference. First, the defeated Central Powers were excluded from the first and most significant phase of the conference in which the Allied and Associated Powers pre-negotiated among themselves the treaty conditions to be presented to the Central Powers. Only once agreement on a text was reached was it presented to the defeated power for acceptance. Little if any room was left for the latter power to negotiate or amend the text. In the case of the Versailles Peace Treaty with Germany, the Allies took almost four months to prepare the text—with an interruption of the negotiation at the top level because of the absence of Lloyd George and Wilson from Paris between 8 February and 14 March 1919—but only allowed the Germans 15 days to react once they had received the draft on 7 May. Second, whereas the Allied and Associated Powers formed a united front in their negotiations with the Central Powers, the latter were forced to make their peace with their former enemies separately. They were not even allowed the traditional courtesy of including their former allies in their treaties. Since the 16th century, it had been customary for belligerents to include their allies and auxiliaries in their peace treaties. While the legal implications of these inclusion clauses could differ, they were politically important as they prevented an ally or auxiliary from being left to face the revenge of the former enemy on its own once a separate peace had been reached.

13  The negotiations among the Allied and Associated Powers were by far the most extensive, both in terms of time and the depth of discussions. As had already been the case, albeit to a lesser extent, at the Vienna Congress (1815), the proceedings of the conference were highly structured. No less than 52 committees were formed to deal with various specialized issues. The Council of Ten coordinated the negotiations; it consisted of the leaders and foreign ministers of France, Great Britain, Italy, Japan, and the United States. After the return of Lloyd George and Wilson, the Council was reduced to four, leaving out the Japanese Prime Minister and the foreign ministers. Displeased with the territorial concessions his allies were willing to make, the Italian Prime Minister Vittorio Orlando (1860–1952) left the conference in April, thus leaving the ‘Big Three’ to conclude the negotiations. The plenary session of all the represented ‘Allied and Associate Powers’ was hardly left anything to say and was only presented with the text hours before it was submitted to the Germans. This meant that all other powers had to make their points by appearing before the Council of the Great Powers in its different manifestations.

14  The five Paris Peace Treaties all held the same structure and contained many identical or similar provisions. Part I contained the 26 articles that formed the Covenant of the League of Nations, as well as the list of its 45 founding members—the 32 Allied and Associated Powers and 13 Neutral States. Part II and III contained the territorial settlement and main political issues for each of the defeated powers in Europe whereas Part IV dealt with the interests of the defeated powers outside Europe. In Part V, far-reaching restrictions were imposed upon the military, naval, and air forces the defeated power would be allowed to have in the future. Part VI dealt with prisoners of war and war graves. Parts VII and VIII subjected the Central Powers to penalties and reparations, which were further elaborated upon in Part IX, ‘Financial Clauses’. The extensive Part X regulated economic relations for the future, whereas Part XI made provisions regarding aerial navigation, Part XII about ports, international watercourses, and railways, and Part XIII regarding ‘Labour’, constituting the creation of the International Labour Organization (ILO). The treaties were concluded by a part containing some miscellaneous provisions, preceded in the Versailles Peace Treaty by a Part XIV on guarantee[s]. The Neuilly Peace Treaty lacked a part on non-European issues. The Sèvres Peace Treaty combined the political interests of the Ottoman Empire in and outside Europe in Part III, but the stipulations on minorities that had been dealt with in Parts III of the other treaties were relegated to a separate Part IV. More importantly, as the Allies did not impose reparations upon the Ottoman Empire, a Part VIII (Reparations) was lacking from the Sèvres Peace Treaty.

15  The five peace treaties did not contain a general peace clause, as had been customary since the Late Middle Ages. In the preambles, however, it was stated that with ‘the coming into force of the present Treaty the state of war will terminate’, and that from that moment onwards, official relations with the defeated power would be resumed.

16  One of the main issues on which the Paris Peace Treaties of 1919 and 1920 departed from the peace treaty practices of the 19th century was in relation to war guilt and reparations. These two issues were closely intertwined. Since the late 18th century, and particularly during the Revolutionary and Napoleonic Wars (1792–1815), it had become customary for the victor of a war to impose a financial indemnification and compensation for war expenses and damages upon the defeated power. These compensations were in no way related to any admission by the defeated power of having committed a wrong, in the sense of having broken the ius ad bellum by resorting to war nor of having broken the ius in bello. The legal basis for these compensations rested in the ius victoriae; they were considered parts of the spoils of war the victor had gained, the right to which was based on its victory and/or the acceptance of it in the treaty. Major peace treaties of the 19th century, such as those of Paris of 1814 and 1815 ending the Napoleonic Wars (Holy Alliance [1815]) and the Frankfurt Peace Treaty (1871) ending the Franco-German War, had contained a provision for the payment of a huge sum of money by the loser, in both cases France.

17  With the exception of the Sèvres Treaty, the Paris Peace Treaties of 1919 and 1920 imposed reparations for war damages suffered by civilians upon the Central Powers, but—with the exception of Belgium—no indemnification for war costs on the part of the victorious States were exacted. This shift is mainly to be explained by the gap that existed between Wilson’s repeated promises that the Allies would not impose ‘punitive damages’—understood by Germany to refer to traditional indemnifications—and the French, Belgian, and British desires to impose huge financial obligations upon Germany. A solution was found in Wilson’s claim from the Fourteen Points and some of his speeches—that had been accepted by the Germans to lay out the conditions under which they sued for peace—that all invaded and occupied territories should be fully ‘restored’. In their message to Germany of 5 November 1918, the Allies had made it known that this would imply ‘that compensation will 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’ (Temperley 133).

18  In the peace treaties, the reparations were made consequential to the claim that the defeated powers were guilty of having imposed the war upon the Allies by their aggression (Art. 231 Versailles Peace Treaty), and thus liable for all the costs and damages arising from it. As such, the reparations—or any other form of compensation—ceased to be consequential to defeat in the war, but were a liability for having committed a wrong in having caused and fought the war. This legal construction was clearly inspired by the law of delict. Art. 232 Versailles Peace Treaty stipulated that because the means of Germany were deemed insufficient for covering all the war costs and damages, it should only provide reparations for the damages suffered by civilians, as well as the war debts of Belgium, which it had promised earlier to pay for. The other four treaties followed the same legal reasoning, although in case of the Ottoman Empire, all reparations were waived (Art. 231 Sèvres Peace Treaty).

19  Another major departure from tradition was to be found in the part entitled ‘Penalties’. Art. 227 Versailles Peace Treaty provided for the prosecution of the German Emperor Wilhelm II for ‘a supreme offence against international morality and the sanctity of treaties’ before an international tribunal. Arts 228 and 229 granted the victors the right to prosecute military persons who had violated the laws and customs of war and persons who had committed crimes against their nationals. These two provisions were also to be found in the other four Treaties of Paris.

20  For the main territorial and political provisions particular to these treaties, see the entries on Versailles Peace Treaty (1919), St Germain Peace Treaty (1919), Neuilly Peace Treaty (1919), and Trianon Peace Treaty (1920). The Sèvres Treaty confirmed the dismemberment of the Ottoman Empire. The new Turkey was little more than a rump State in Central Anatolia, losing all European—except for Istanbul—and Arab possessions of the former Ottoman Empire and all territories east of the Euphrates on the Anatolian plateau.

3.  Soviet Russia and Successor States of the Russian Empire (1920–22)

21  The armistices and peace treaties between the Allied and Associated Powers and the Central Powers forced the latter to abrogate their treaties with Soviet Russia and the other Eastern and Central European States from 1918. As Russia did not partake in the Parisian conference, the political situation in the region was left unsettled. The Western powers refused to recognize the new Soviet regime and actively intervened on the side of its opponents in the civil war of 1917–22. During these years, Soviet Russia concluded peace treaties with several of the new States that had broken away from the Russian Empire. These remained in force once Russia, Ukraine, Belorussia, and the Transcaucasian Soviet Republic had joined in the Union of Socialist Soviet Republics (USSR) by 1923.

22  The German military advances of 1916–18 and the Russian Revolution allowed Finland, the three Baltic States, and Poland to (re)gain their independence. After the collapse of Russian control over Finland following the Bolshevik Revolution, a civil war erupted in Finland between leftist and rightist forces. By May 1918, the conservative side had won. The Soviet intervention on the leftist side in the Finnish civil war left the two countries in a state of war. This was resolved through the Tartu Treaty of 14 October 1920. Russia recognized the independence of the new Finnish Republic on the old territory of the Grand Duchy. Finland ceded some lands in Eastern Karelia but gained with Pestamo an ice-free harbour on the Arctic Ocean.

23  In the wake of the German collapse, Estonia declared independence on 12 November 1918. With the Tartu Treaty of 2 February 1920, Soviet Russia recognized the independence of Estonia. Latvia declared its independence shortly after Estonia, on 18 November 1918. During 1919, Latvia had to fight for its independence against the German-Baltic army. Supported by the Estonians, the Latvians finally prevailed. The Riga Peace Treaty of 11 August 1920 ensured Russian recognition of Latvia’s independence. After the withdrawal of the German army in 1919, communists took power in Lithuania. During the Polish-Russian War of 1920, the Polish brought the regime down, but Lithuania remained an objective ally of Russia in the war. With the Moscow Treaty of 12 July 1920, Russia recognized the new State.

24  In 1919, war erupted between the newly independent Poland and Soviet Russia. After the initial successes of the Polish and their Ukrainian allies, the Russian counter-offensive pushed the Polish back and threatened Warsaw. The Western allies intervened diplomatically and tried to propose a border, known as the Curzon Line, but hostilities went on. By late 1920, the Polish had regained the upper hand. In the Riga Peace Treaty of 18 March 1921 (‘Riga Peace Treaty II’), Poland was granted over 100,000 square km of territories up to 200 km east from the Curzon Line. Poland and Soviet Russia also recognized the independence of Ukraine and Belorussia (Art. 2 Riga Peace Treaty II). Compensation was waived in Art. 8 of the treaty, but Poland received a money indemnification for the loss of title to her active participation in the economy of Russia.

25  The abrogation of the Brest-Litovsk Peace Treaty with Russia left the state of war with Germany in existence. The Rapallo Treaty (1922) led to the normalization of relations between the two States and the waiver of all compensations for war costs and damages.

4.  Dismemberment of the Ottoman Empire (1920–23)

26  The armistice of Mudros between the Ottoman Empire and the Western allies had not led to a complete cessation of hostilities. The armistice left the British and their Arab allies in control of the Arab possessions of the former Ottoman Empire. In April 1919, Italy invaded Western Anatolia to strengthen its territorial claims at the future peace conference, followed by the Greek landing in Izmir. The Western allies landed a force in Istanbul in April 1920. The Treaty of Sèvres confirmed the dismemberment of the Ottoman Empire and left the Sultan with most of Anatolia west of the Euphrates and Istanbul (Dismemberment of States). Iraq, Syria, Transjordan, Palestine, and Lebanon became mandates of the British and the French, while the Arabian Peninsula gained its independence under Arab princes, among which were those from the house of Saud. Although the Sèvres Peace Treaty was never ratified from the Ottoman-Turkish side, the League of Nations confirmed the British and French mandates.

27  The Sèvres Peace Treaty had also affirmed the independence of Armenia and had forced the Ottomans to cede large tracks of Eastern Anatolia to Armenia. After his military victories, Mustafa Kemal forced the Armenians to recognize the old borderline between Russia and the Ottoman Empire by the Alexandropol Treaty of 2 December 1920. Meanwhile, the Turks regained control of Kurdistan north of Iraq and Syria that had become autonomous under the Sèvres Peace Treaty. With the Ankara Treaty of Friendship of 16 March 1921, relations with Soviet Russia were normalized and all capitulations cancelled.

28  The Turkish victory over the Greeks at Sakaria in August 1921 induced France to cut its war effort and to make peace at Ankara on 20 October 1921. The border between Turkey and Syria was corrected to the advantage of the former. Mustafa Kemal then turned upon the Sultan at Istanbul and the Allied forces along the straits (Dardanelles and Bosporus), forcing the Allies—Britain, France, and Italy—into an armistice at Mudanya on 11 October 1922, to which Greece acceded three days later. This left Mustafa Kemal free to take Istanbul and abolish the Sultanate. Mehmet VI left for exile on 18 November 1922. Meanwhile, peace negotiations were started with the Allies that led to the Lausanne Peace Treaty of 24 July 1923.

5.  United States and Central Powers (1921)

29  The non-ratification of the five Parisian Peace Treaties by the United States left the state of war between the US and the Central Powers unsettled. The rejection of the peace treaties by the United States Senate was mainly inspired by its reluctance to join the League of Nations and thus accept a permanent and possibly military commitment to the European peace settlement. Separate peace treaties were made at Vienna with Austria on 24 August 1921, with Germany at Berlin on 25 August 1921 (Germany-United States Peace Treaty), and with Hungary at Budapest on 29 August 1921 that ended the state of war. Under these treaties, the United States received all the rights the original Paris Peace Treaties had granted them and imposed all the same duties upon the Central Powers as the original peace treaties had done, including reparations (Art. 1 Germany-US Peace Treaty). The United States exempted themselves, however, from all obligations arising out of Part I (League of Nations), and Parts II, III and IV (territorial and political issues) from the Parisian Peace Treaties, so that they were under no obligation to intervene to uphold the peace settlement in and outside Europe (Art. 2 Germany-US Peace Treaty).

C.  Significance of the Peace Treaties

30  The peace treaties after World War I largely redrew the maps of Europe and the Middle East and brought an end to the colonial empire of Germany in Africa and the Pacific. They confirmed the collapse of three major empires in Europe and the Middle East—Austria-Hungary, Russia, and the Ottoman Empire. In Central and Eastern Europe, several new States emerged or regained their independence, including Finland, the three Baltic States, Poland, Czechoslovakia, Hungary, Austria, and Yugoslavia. By 1923, with the foundation of the USSR, the Soviets had regained a large part if certainly not all of the former imperial possessions in Europe and the Caucasus. The demise of the Ottoman Empire led to the foundation of the Turkish Republic and opened the way for the formation of several States on the Arabian Peninsula. The Parisian Peace Conference denied the Arabs their dream of a unified Arab State, but brought the lands between Turkey and the Peninsular under British and French control. Out of their mandates grew the modern States of Iraq, Syria, Lebanon, (Trans)Jordan, and Israel/Palestine.

31  From a juridical perspective, most of the peace treaties of 1918–23, with the exception of the five Parisian Peace Treaties, stood firmly in the early modern and 19th-century tradition of peace treaties. The doctrine and practice of peacemaking reflected the doctrine of the ius ad bellum that recognized the right of sovereign States to resort to armed force and warfare if they deemed this necessary to protect or enforce their interests and rights. Since the early 17th century, doctrine had upheld that a war was legal and had legal effects—eg granting the benefits of the ius in bello without discrimination to all sides—as long as it was waged by sovereign powers and it had been formally declared. By consequence, peace treaties were made on the assumption that all—sovereign—belligerents had had a right to wage war. Therefore, the peace treaties of the Early Modern Age and the 19th century contained no attributions of guilt for the war. Liabilities of all costs and damages during the war were covered by the amnesty clauses that were included in all peace treaties between the 16th and 18th centuries. During the 19th century, these amnesty clauses disappeared but were held to be implied. From the late 18th century onwards, it became customary for victors to impose a money compensation for war costs and damages upon the defeated powers. This did not conceptually contradict the positivist doctrine as these were held to be part of the spoils of the victor rather than consequential to any attribution of guilt by the defeated power.

32  The five Parisian Peace Treaties of 1919 and 1920 radically diverted from the positivist doctrine of war and peace in three different ways. First, they included a one-sided attribution of guilt for the war to the defeated side that was found guilty of aggression. Second, they imposed a general liability for costs and damages of the war because of that. Third, they granted the victors the right one-sidedly to prosecute the sovereign ruler of the enemy for wrongs committed against international law and different other categories of persons for violations of the ius in bello and for criminal acts.

33  The latter made an inroad into the principle of State sovereignty and can be considered a precedent for the international prosecution for international crimes, in particular war crimes, crimes against peace, and crimes against humanity as it arose after World War II.

34  The first two seem to some extent a return to the discriminatory character of peace, bound up with the medieval doctrine of just war. Under the just war doctrine, only one side can be the just party. War is considered an instrument of justice of the just side against the unjust side. War, which is inherently discriminatory, should thus be concluded with a just, discriminatory peace. This implies the attribution of guilt to the unjust side, the attribution of the object of war to the just side, and the general liability for all war costs and damages by the unjust side.

35  Although the Paris Peace Conferences took on some of the features of a just peace, there was no complete return to the tradition of the just war. The peace treaties were not reflecting a conscious, sudden turn to a radically different concept of war as that of 19th century positivist doctrine. But they did constitute a stepping stone in an ongoing change of the doctrine and practice of the ius ad bellum that would find its accomplishment in the Kellogg-Briand Pact (1928) and the United Nations Charter. First, the relevant Arts 231 and 232 Versailles Peace Treaty were the somewhat pragmatic or opportunist solution to the problem of the discrepancy between the American President’s promises and the Franco-British expectations regarding financial compensation. Second, Art. 231 blamed Germany for the war because it had committed an act of aggression. To some extent, this did not constitute a radical break from tradition. Until the late 18th century, most writers had upheld the doctrine of just war as much as that of legal war. It was made possible to work with two contradictory doctrines regarding the right to resort to war because one was said to pertain to the natural law of nations and the other to the positive law of nations. In this, doctrine reflected the duplicity of early-modern State practice. Whereas States recognized the legal effects of any war in the sense that they granted the benefits of the ius in bello to their enemies and did recognize the rights of the former enemy to have fought the war in their peace treaties, they continued to justify their wars in terms very similar to or reminiscent of that of the just war. For centuries, the most common justification for war had been that of waging defensive war against the aggression and/or perfidy—the violation of treaty obligations—of the enemy. In making reference to the violation of the sanctity of treaties (Art. 227) and aggression (Art. 231), the Parisian peace treaties tapped into these traditions but now, for the first time in centuries, attached legal consequences thereto at the level of peacemaking. Third, Part I of the Paris Peace Treaties that constituted the Covenant of the League of Nations did somewhat restrict the right to resort to war by imposing rules in relation to the use of pacific means to settle disputes before a State could resort to war (Arts 11–16) and through Art. 10 regarding ‘external aggression’ against ‘the territorial integrity and existing political independence of all Members of the League’. Whereas the exact implications of Art. 10 Paris Peace Treaties were and are much debated, it certainly formed a stepping stone towards moving the prohibition of wars of aggression from the field of natural law (or political morality) to that of positive international law.

36  In the light of pragmatism, problems arose with regard to the enforcement and execution of the Versailles Peace Treaty, because of the diverging visions and purposes of the involved powers, ie, Britain, France, Germany, and the United States. An important anomaly of the Versailles Peace Treaty was that the treaty did not provide adequate sanctions, which were necessary in case of violation of the treaty, ie, in a situation of use of force. Further, the harsh indemnity provisions of the Versailles Peace Treaty, which instigated Germany paying unspecified reparations, reduced Germany’s opportunities to improve its situation, socially, economically, financially, and politically. The regime of reparations, in which the individual interests of the involved States played a key role, proved to be defective because of the weak performance of the Allied Powers in respect of the enforcement of the provisions and the German refusal to comply with the articles concerned. Germany never reconciled itself with the Versailles Peace Treaty because of its enforced disarmament, the unspecified reparations, the loss of territory, and what it saw as the inconsequential application of the right of self-determination, its obligation to hand over war criminals, and its enduring isolation. Economist John Maynard Keynes, opponent of the harsh reparation clauses in the Versailles Peace Treaty, even blamed the treaty for Germany’s vindictiveness and revisionism.

37  Lastly, the Paris Peace Treaties showed the first signs of a system of minority rights and protection in the framework of the League of Nations (Minority Protection System between World War I and World War II). Although no universal prescription of minority rights was provided for in the treaties, some key points were articulated with regard to the recognition of minorities, the guarantee of minority rights for humanitarian and pragmatic reasons, the provision of procedures to implement the rights, the encouragement of fundamental rights, and the mentioning of autonomy rights for certain groups of people. The object of the system of minority protection was to give assurance to populations which differ from the majority population in a State in terms of race, language, or religion, to live alongside the majority population and cooperate with it, while the distinguishing characteristics of the group have to be preserved and the ensuing special needs have to be satisfied. However, in the light of nationalism and the protection of national interests, Great Britain, France, and Germany withdrew from the scope of application of the provisions in relation to the protection of minorities, especially those on self-determination. Contradictory pressures from the United States and the European Allied Powers led to a disappointing compromise on minority rights in the treaties that, in the end, weakened the prospects for an effective enforcement of minority rights in Europe.

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