Addressing a gap in existing literature, this book provides an introduction to nuclear weapon states and their relationship with the global nuclear order/disorder paradigm. It explores four main themes and aims to: 1. conceptualise the dichotomous paradigm of global nuclear order/disorder; 2. outline the different phases of global nuclear order/disorder from 1945 to present; 3. address the Nuclear Non-Proliferation Treaty (NPT) and the wider international nuclear non-proliferation regime; 4. provide an overview of every nuclear weapon state’s national nuclear doctrines throughout the years. The book will be of much interest to students of nuclear proliferation, global governance, security studies, Cold War studies, foreign policy and IR, more generally.