This collection of papers rigorously examines the current place of deterrence in international security relations, delivering the best of contemporary thinking. This is a special issue of the leading journal Contemporary Security Policy. It shows how and why nuclear deterrence was the central organizing mechanism for international security relations in the second half of the twentieth century. It has been replaced by a new global security environment in which the central role of deterrence, both nuclear and otherwise, appears to have diminished. The Cold War has been succeeded by a new state of play. This book will be of interest to students of military and naval history and security studies.