If, at the beginning of the twentieth century, thanks also to the influential works of Triepel and Anzilotti, the law of state responsibility came to be regarded as a distinct field, it was only in the period between the two world wars that this area of international law became the object of an intense scientific debate. The present contribution aims to assess the development of the law of state responsibility until 1945 by focusing on the events that provided a major impulse for this development, on the attempt at codification, on the case law of international courts and tribunals, and on the new general theories developed by authors such as Strupp, Kelsen, Lauterpacht, Eagleton and Ago. While the contribution aims to deal comprehensively with the law of state responsibility and its development in the period under consideration, particular emphasis will be placed on three issues: the problems associated with attribution of wrongful conduct; the consequences of international responsibility, and in particular the debate over the role of sanctions against wrongful conduct – the early signs of the emergence of a multilateral dimension of state responsibility.