During the 1950s, the West European Socialist parties found themselves divided on the question of European integration . This cleavage not only separated different national parties from each other but caused deep and painful rifts within national parties themselves. The related controversies form the core of this volume, consisting of a synthetic analysis, 13 national case studies, and testimonies of three eyewitnesses - Marinus van der Goes van Naters, Christain Pineau and Mario Zagari - who were closely involved with the events described. The book deals with an important aspect of the prehistory of the European Economic Community and aims to provide a useful tool for its comparative study.