The purpose of this volume is to explore the medieval inheritance of modern international relations. Recent years have seen a flourishing of work on the history of international political thought, but the bulk of this has focused on the early modern and modern periods, leaving continuities with the medieval world largely ignored. The medieval is often used as a synonym for the barbaric and obsolete, yet this picture does not match that found in relevant work in the history of political thought. The book thus offers a chance to correct this misconception of the evolution of Western international thought, highlighting that the history of international thought should be regarded as an important dimension of thinking about the international and one that should not be consigned to history departments.