Abstract: Hugo Grotius (1583–1645), ‘the miracle of Holland’, was famous as a child prodigy, theologian, historian, poet, jurist, Dutch political figure, escaped political prisoner, and finally as Sweden's ambassador to France. He is especially known for his major books on international law and practice, Mare Liberum (1609) and De Jure Belli ac Pacis (1625).This book critically reappraises his contributions both to international law (called ‘the law of nations’ in his day) and to international relations. His contributions are examined in relation to his predecessors and in the context of the wars and controversies of his time. This book also assesses the strengths and weaknesses of what is often called a ‘Grotian tradition’ of thought about international law and relations—one which accepts the sovereignty of states, but at the same time stresses the existence of shared values and the necessity of rules.This collection illuminates enduring problems of international relations: the nature of international society and its institutions, the equality of states, the role of natural law, the lawfulness of war (jus ad bellum), the means of pursuing war (jus in bello), collective security, military intervention, the rights of the individual, and the law of the sea.While first and foremost a study in the field of international relations, this is also a significant contribution to the history and theory of international law; and to the history of the early seventeenth century, when the Dutch Republic, and the European states system generally, were emerging in their modern forms, and when the Thirty Years War impressed on Grotius and others the need for restraint in war.

Keywords: De Jure Belli ac Pacis, Dutch Republic, European states system, Grotian tradition, Huig de Groot (alternative spelling), Hugo Grotius, international law, international relations, international society, jus ad bellum, jus in bello, law of nations, law of the sea, laws of war, Mare Liberum, military intervention, natural law, Netherlands, Thirty Years War