This volume offers a critical historical assessment of the negotiation of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and of the origins of the nonproliferation regime. The NPT has been signed by 190 states and was indefinitely extended in 1995, rendering it the most successful arms control treaty in history. Nevertheless, little is known about the motivations and strategic calculi of the various middle and small powers in regard to their ultimate decision to join the treaty despite its discriminatory nature. While the NPT continues to be central to current nonproliferation efforts, its underlying mechanisms remain under-researched. Based on newly declassified archival sources and using previously inaccessible evidence, the contributions in this volume examine the underlying rationales of the specific positions taken by various states during the NPT negotiations. Starting from a critical appraisal of our current knowledge of the genesis of the nonproliferation regime, contributors from diverse national and disciplinary backgrounds focus on both European and non-European states in order to enrich our understanding of how the global nuclear order came into being. This book will be of much interest to students of nuclear proliferation, Cold War history, security studies and IR.