This book offers valuable insights into the causes and consequences of nuclear proliferation. Through the development of new datasets and the application of cutting edge research methods, contributors to this volume significantly advance the frontiers of research on nuclear weapons. Essays in this volume address why states acquire nuclear weapons, why they engage in nuclear cooperation, and also explore the relationship between nuclear weapons possession and a variety of security and diplomatic consequences. In addition to accelerating the development of an empirical research agenda, the chapters combine to form a coherent storyline that shows nuclear technology and capabilities have been under appreciated as a cause of proliferation in recent scholarly literature. For scholars and practitioners alike, there is a strategic logic to nuclear assistance that is essential to understand. Moreover, several of the essays show that the consequences of nuclear proliferation are more complex than is conventionally understood. Nuclear weapons can have both stabilizing and destabilizing effects. Nuclear weapons may simultaneously cause their owners to become more influential, more successful in the wars they choose to fight, and to have less intense conflicts, when these conflicts occur. This book will be of much interest to students of arms control and nuclear proliferation, war and conflict studies, security studies and IR.