The nuclear Nonproliferation Treaty (NPT) is the cornerstone of nonproliferation and disarmament efforts, yet its negotiation and success was not inevitable. This book aims to address the developments that led to the negotiation of the treaty, examine its implementation, and address challenges that the NPT faces going forward. It begins with an overview of precursor efforts to establish international limits on nuclear weapons and why these efforts failed. It also looks at the changes in the political environment and technical advances, which together increased the threat of proliferation and drove states to negotiate the NPT. The second chapter considers the negotiation of the treaty itself and looks at the gap between US and Soviet positions on key areas like alliance control of nuclear weapons, and how the two governments found common ground on nonproliferation language. It also explores the critical role played by the non-aligned movement to push inclusion of disarmament provisions that would become the foundation for Article VI of the treaty and the hesitancy of nuclear-armed states to support disbarment language and timelines. Chapter 3 of the book focuses on implementation of the NPT and its initial successes in heading off states with nuclear weapons research programs. It addresses how the treaty responded to challenges like the dissolution of the Soviet Union and gaps identified by the illicit nuclear weapons programs in Iraq and North Korea in the early 1990s. Chapter 3 also includes a section on the debate in 1995 over extending the treaty indefinitely, and the compromises reached to satisfy the concerns of the non-nuclear weapon states. Finally, Chapter 4 addresses some of the outstanding challenges to the NPT that remain unresolved, such as the continued failure to convene a conference on the Middle East WMD-free zone and specify the consequences of withdrawing from the NPT, and repurposing civilian nuclear technology transferred under the treaty weapons purposes. It also looks at how the ban treaty under negotiations in the United Nations will support or undermine the NPT’s objectives.