1. Introduction

This introductory chapter discusses the development of the international law. It begins by tracing the development of the law of nations, now known as (public) international law, which grew out of the tradition of the late medieval ius gentium. Over the course of the twentieth century, international law underwent a profound process of expansion. Developments included, inter alia, the creation of international organizations of universal membership with treaty-making powers, a detailed elaboration of the law of the sea, the establishment of permanent bodies for the settlement of international disputes, the prohibition on the use of force by states, and the emergence of various sub-disciplines or specialist areas of work and study.