Jump to Content Jump to Main Navigation

Letter from the Editor

Treaties and international history

An introduction to Oxford Historical Treaties

The use of treaties to organise international relations is almost as old as recorded history itself. The first documented international agreements stem from the Sumerian civilisation and date back to the middle of the 3rd millennium BCE. Treaties are a universal occurrence in human history. All major civilisations have known them. Also, in the historical encounters between different civilisations, such as the European discoveries in Africa, America, and Asia, treaties ranked among the first instruments used to establish relations.

From their remotest origins, treaties have fulfilled numerous different functions. Their contents are as diverse as the substance of human contacts across borders themselves. From pre-classical Antiquity to the present, they have not only been used to govern relations between governments, but also to regulate the position of foreigners or to organise relations between citizens of different polities. An attempt at classifying historical treaties according to their purpose and content leads to the following typology:

  1. Treaties establishing friendly relations between polities in times of peace, such as treaties of friendship;
  2. Treaties ending war and settling disputes, such as peace treaties, border treaties, or arbitration treaties;
  3. Treaties regulating warfare, such as agreements on prisoners of war, surrender, arms control, or the rights of neutrals;
  4. Treaties of alliance;
  5. Treaties of subjection and empire, such as the Roman deditio (surrender) or treaties of protectorate or cession of sovereignty;
  6. Constitutional treaties, such as treaties of confederation or for the foundation of international organisations;
  7. Treaties on rights of private citizens, including treaties on matters of trade, navigation and transport;
  8. Treaties on general issues of international law or common concerns of the international community, such as environmental treaties.

Treaties are essential to the study of international history, whether its political, economic, legal, social, or cultural dimensions are concerned. To the student of the history of international law, they have an additional significance. Treaties are significant informative sources of international law, as they apply existing international law and thus bear testimony of it. They shed light both on the law of treaties as well as on many areas of substantive international law. But besides this, treaties are also constitutive, formal sources of international law, in the sense that they create new rules of international law. This is not only true for the multilateral law-making conventions of the late 19th, 20th, and 21st centuries, but also for the mass of – mostly bilateral – treaties of prior eras. Since older treaties often served as the primary source of inspiration for a new treaty throughout most periods and regions in history, treaties were highly repetitive and standardised. Through standardised practice, they served a crucial role in the formation of customary international law. For instance, before its codification in the 1969 Vienna Convention on the Law of Treaties, the formal law of treaties was for a large part produced through standardised practices from treaty-making itself.

The rise of the modern states system in Early Modern Europe (the 16th-18th centuries) signalled the heyday of treaties. The rejection of the universal authority of the pope and of canon law during the Reformation and the emergence of powerful dynastic ‘states’ collapsed the hierarchical order of medieval Christianity. In its stead came a new order which was premised on the principle of state sovereignty and based on horizontal agreements between the members. Treaties, as well as customary law, replaced the authoritative doctrines of canon, Roman, and feudal law as primary formative sources of ‘international law’. The backbones of the ‘classical law of nations’ or the jus publicum Europaeum of the late 17th and 18th centuries were the networks of bilateral treaties between the princes and republics of Europe, as well as the common principles, values, and customary rules of law that could be induced from the shared practices that were employed in diplomacy in general and in treaty-making in particular. Some treaties, particularly the sets of peace treaties that were made at multiparty peace conferences such as those of Westphalia (1648, from 1 CTS 1), Nijmegen [Nimeguen] (1678/79, from 14 CTS 365), Rijswijk [Ryswick] (1697, from 21 CTS 347), Utrecht (1713, from 27 CTS 475), Aachen [Aix-la-Chapelle] (1748, 38 CTS 297) or Paris/Hubertusburg (1763, 42 CTS 279 and from 42 CTS 347), gained special significance and were considered foundational to the general political and legal order of Europe. The role of treaties in the formation of European order and law was such that contemporary (Mably 1748) as well as later (Hosack 1882; Wheaton 1845) historians reduced the study of the law of nations in practice to that of treaties.

It is no surprise that it was in this period that the first major collections of treaties were published. Whereas these collections made treaties publicly available, their primary targeted audience were diplomats, government officials, and other practitioners of international relations and law. Most of these collections only covered the treaties entered into by one particular prince or republic, but some were more encompassing and were European in scope. For a long time, the most important collection was undoubtedly that made by the French publisher Jean Dumont (1667–1727), which was published in the Dutch Republic in 16 volumes between 1726 and 1731. It contained thousands of treaties, and some other documents relevant to the law of nations such as declarations of war and arbitral awards, ranging from the early Middle Ages to 1730. Its major ‘successor’ was the collection initiated by the German professor of the law of nations, Georg Friedrich von Martens (1756–1821). The oldest document in the Martens collection dated from 1761. His series was continued all through the 19th century until 1920, when the League of Nations Treaty Series began. Also, its scope expanded beyond Europe. Some treaties predating 1761, which had been missed by Dumont, were included in later supplements

Taken together, these series had not been surpassed until Clive Parry (1917-1982), Professor of International Law at Downing College, Cambridge University, published The Consolidated Treaty Series. Parry, as he explained in his Preface to volume 1, wanted to make historical treaties more readily accessible from the period before the official publications by the League of Nations and the United Nations. He believed that the collections by Dumont, Martens, and others were not sufficiently available to scholars. Moreover, referring to Dumont’s ‘somewhat optimistic opinion of the linguistic facility of his readers’, Parry wanted to provide international readership as much as possible with an English or at least a French translation of the texts. Between 1969 and 1981, Parry published over 200 volumes – considerably more than he had anticipated – containing around 16,000 treaties ranging from the period between 1648 and 1920. Thereby he surpassed Martens and Dumont in usefulness, except for the volumes of Dumont that cover the period before 1648. For pre-Westphalian treaties, Dumont remains the most comprehensive collection to this day.

The decision by Oxford University Press to digitize Parry’s Consolidated Treaty Series is a major event for any student of the history of international law and relations of the Early Modern Age and the 19th century. Although many libraries hold a copy of Parry’s collection, this project of digitisation will considerably lower practical barriers to access the vast amount of information stored in these treaties. Traditionally, the historiography of international law has been focused on intellectual developments to the detriment of the study of diplomatic and legal practice. One explanation that has been offered for this practice is the daunting challenge of finding and mastering the vast and widely dispersed relevant source material (Verzijl 1968). Oxford Historical Treaties has the potential to make a significant contribution towards helping students of the history of international law to expand their scope to historical state practice, this at the time when the interest in this field is blossoming.

By making The Consolidated Treaty Series digitally accessible, Oxford University Press has done the field of international relations and law an important service. But the project will not stop at that. There are plans to expand the database by adding treaties which did not find their way into Parry’s collection. The index to the series also included a list of texts from after Westphalia which had not been reprinted therein. But the most important addition would be to expand it to pre-Westphalian treaties.


Amnon Altman, Tracing the Earliest Recorded Concepts of International Law. The Ancient Near East (2500-330 BCE) (Leiden and Boston: Brill/Nijhoff, 2012).

Jean Dumont, Corps universel diplomatique du droit des gens; contenant un recueil des traitez d’alliance, de paix, de trêve, de neutralité, de commerce, d’échange … depuis le regne de l’Empereur Charlemagne jusques à present; avec les capitulations impériales et royales; les sentences arbitrales … Le tout tiré en partie des archives de la très-auguste Maison d’Autriche … (16 vols., Amsterdam/The Hague: Brunel/Husson & Levier, 1726-1731).

John Hosack, On the Rise and Growth of the Law of Nations, as established by general usage and by treaties, from the earliest time to the treaty of Utrecht (London: John Murray, 1882).

Gabriel Bonnot de Mably, Le droit public de l'Europe, fondé sur les traitez conclus jusqu'en l'année 1740 (2 vols., Amsterdam: Uytwerf, 1748).

Peter Macalister-Smith and Joachim Schwietzke (eds.), Treaties, Treaty Collections and Documents on Foreign Affairs. From Sun King Suppilulima I to the Hague Peace Conferences of 1899 & 1907. An annotated bibliography (Berlin and Munich: Gerhard Weinert, 2002).

Martens, Georg Friedrich von (ed.), Recueil des principaux traités d’alliance, de paix, de trêve, de neutralité, de commerce, de limites, d’échange, etc. conclus par les puissances de l’Europe, tant entre elles qu’avec les puissances et états dans d’autres parties du monde depuis 1761 jusqu’à présent. Tiré des copies publiées par autorité, des meilleures collections particulières de traités, et des auteurs les plus estimés (7 vols., Göttingen: Dieterich, 1791-1801), continued in other series until 1969.

Henry Wheaton, History of the Law of Nations in Europe and America from the Earliest Times to the Treaty of Washington, 1842 (New York: Gould, Banks, and Co., 1845).

J.H.W. Verzijl, ‘Research into the History of the Law of Nations’, in International Law in Historical Perspective vol. 1 (Leiden: Nijhoff, 1968) 400–43.


Prof. Dr. Randall Lesaffer
Full Professor of Legal History
Department for Public Law, Jurisprudence and Legal History
Tilburg Law School
Editor of Oxford Historical Treaties