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Treaties in Declarations and Manifestos of War

By: Randall Lesaffer

In the second half of 2017, the Yale law professors Oona Hathaway and Scott Shapiro published a remarkable book on the history of international law. Written with the pace and enthralment of a novel, The Internationalists and Their Plan to Outlaw War presents a breath-taking narrative of four hundred years of the laws of war and peace. The main thrust of the book is that the move towards the prohibition of force which was crystallized in the Kellogg-Briand Pact of 1928 and the United Nations Charter of 1945 is the keystone of the new world order that arose in the middle of the 20th century. The authors argue that the movement for the ‘outlawry of war’ overhauled the old world order and set the conditions for the creation of a new international order. War lost its function as an instrument of dispute settlement between states and as a means to conquest and expansion, and was replaced by more peaceful forms of coercion, such as economic sanctions and collective pressure. At the same time, this change explains the gradual decline of the state and the rise of intra-state armed conflict.

Hathaway and Shapiro contrast the new world order of the second half of the 20th and the beginning of the 21st centuries with the old world order, which arose in Early Modern Europe. Under this old order, for which they cast the Dutch humanist Hugo Grotius (1583–1645) as the major, original intellectual expounder, war was a legitimate instrument for states to settle disputes about rights in the absence of a higher authority to turn to. To illustrate the function of war as a substitute for dispute settlement, the authors discuss the justification of war in Early Modern Europe in a chapter on declarations and manifestos of war.

The authors based the 25-page chapter on an impressively wide set of declarations and manifestos of war. With the help of a group of Yale Law School students and the Lillian Goldman Law Library, they amassed the texts of several hundred declarations and manifestos of war ranging from 1492 to 1945. The list includes a great variety of, according to the definition of the collectors, public statements issued by a sovereign against another sovereign to explain the reasons for resorting to war. Hathaway and Shapiro made their collection available to the public in a searchable database that contains scans of all the declarations and manifestos that they retrieved; this database can be freely accessed through the site of the Lillian Goldman Law Library.

With their initiative, Hathaway and Shapiro have done a great service to the academic community of historians of international relations and law. Back in 1985, the German historian Konrad Repgen called for the study of declarations and manifestos of war from Early Modern Europe as a major source of diplomatic history. Princes and governments in Early Modern Europe generally made great efforts to justify resort to war and force in public. For this, they not only issued a declaration of war to the enemy, stating their reasons, but also had more elaborate manifestos printed that were given wide distribution among their officials, subjects, and foreign audiences. During the 19th and 20th centuries, the form of these public justifications changed, but governments continued to argue their case in public when taking up arms. These justifications often included a statement that the war served to uphold and enforce the rights of the state in the face of their violation or denial by the enemy.

In the view of Repgen, the analysis of these declarations and manifestos of war would be of use for a study on the causes of war. It took more than two decades before any scholar took up the challenge laid out by Repgen and committed to a comprehensive history of declarations and manifestos of war. As Repgen had already indicated, one of the difficulties for this kind of project was that these texts had to be collected from dozens of different libraries and archives. To date, two extensive studies of early-modern declarations and manifestos of war have seen the light of day: that of Bernd Klesmann on 17th-century wars (2007) and the more wide-ranging one of Anuschka Tischer (2012) on the whole Early Modern Age.

As has been shown in the works of Klesmann and Tischer, of several other authors who studied distinct declarations and manifestos of war, and now of Hathaway and Shapiro, declarations and manifestos of war are not only important primary sources for the history of international relations, but also of international law. They offer an insight into the practice of international law by states in two different ways.

Firstly, public justifications of war are an important source for those seeking understanding of the applicable use for force law, the jus ad bellum, in a given period. In particular, the collective and comparative perusal of a series of declarations and manifestos of war, in conjunction with the comments of writers on the law of nations, casts light on the normative framework(s) that governments used to legitimate their actions, which were also expected to be acceptable to the international audience of addressees of these statements.

Secondly, declarations and manifestos of war can also provide information about the value, significance, and use of treaties in state practice. Whereas early-modern and later justifications of war often combined arguments of a political and legal nature, they more often than not contained a reference to certain rights of the state that the enemy had ignored or injured. Among these, the violation of treaty obligations, particularly deriving from previous peace treaties, loomed large. Although a breach of a concrete treaty obligation was rarely found to be sufficient reason for war, numerous declarations and manifestos of war listed instances of violations of treaties. These had a double function. They formed part of a wider argument to prove the sustained enmity of the opponents, the enemy’s desire to damage or destroy one’s own state, and the absolute necessity to stop this by a full-out war. Moreover, they rendered clear and concrete evidence of the violation of a right, which constituted a just cause—causa justa—for war. Thereby the material condition for waging a just war was fulfilled. The wider political argumentation was made to prove that the conditions of proportionality and necessity, and of the righteous intentions of the belligerent, were met. The many references to treaties of peace, commerce, and alliance in war declarations and manifestos make the latter into prime sources to study the effective role of treaties in international relations and law.

The declaration of war by the Dutch Republic against the France of Louis XIV (1638–1715) at the inception of the War of the Spanish Succession from 1702 offers an excellent example of how allegations of treaty violations were used in a variety of ways to justify war. The declaration contained two accusations of treaty violations by the French. The first referred to France’s refusal to implement its duties under the Treaty of Commerce, Friendship and Navigation, which it had made on 20 September 1697 with the Dutch Republic at the peace conference of Ryswick [Rijswijk] (21 CTS 371). The declaration of 1702 claimed that the French had never upheld their obligations with regard to import and export tariffs or their commitment not to impose any taxes on Dutch merchants and residents in France because they were foreigners (Articles 5 to 8). This accusation implied that France had directly injured several rights of the Dutch Republic, giving it a concrete just cause for war.

Under the traditional just war doctrine, such a concrete cause was a necessary but insufficient reason to resort to war. For the war to be just, it needed also to be shown that the war was necessary to attain an essential goal. This the declaration sought in the wider political context, which justified the war as a necessary step to uphold the sovereignty of the Dutch Republic, and that of Christian Europe at large. The underlying reason for the war was that Louis XIV, by accepting the inheritance to the entire Spanish monarchy for his grandson Philippe of Anjou (1683–1746), was seeking the domination of Europe and the encroachment on the liberty and sovereignty of all other European states. Here, a second reference to a breach of a treaty by the French appeared. This concerned the Second Treaty of Partition between France, Great Britain and the Dutch Republic of 25 March 1700 (22 CTS 471), whereby France had made a concession that it would satisfy itself with only part of the Spanish succession. While this constituted another instance of a breach of treaty, in this instance less focus was placed on the fact that this constituted a violation of a right of the Republic. It was mentioned as another indication of the duplicity of the French king, but above all to illustrate his insatiable ambition to domineer Europe. Here, the breach of treaty served the wider political justification of the war.


Oona A. Hathaway and Scott J. Shapiro, The Internationalists and Their Plan to Outlaw War (London: Allen Lane 2017).
Bernd Klesmann, Bellum Solemne. Formen und Funktionen europäischer Kriegserklärungen des 17. Jahrhunderts (Mainz: Verlag Philipp von Zabern 2007).
Anuschka Tischer, Offizielle Kriegsbegründungen in der Frühen Neuzeit. Herrscherkommunikation in Europa zwischen Souveränität und korporativem Selbstverständnis (Berlin: LIT Verlag 2012).