Understanding how leaders make foreign policy and national security decisions is of paramount importance for the policy community and academia. This book explores how leaders such as Trump, Obama, Netanyahu and others make decisions using the Applied Decision Analysis (ADA) method. The chapters gathered here analyse the decisions made by key political figures around the world, past and present, in order to shed light on how these decisions are made and what policy implications they have for their own and other nations. Several chapters also focus on military decision making, including around pivotal times in history including the second world war and the evolution of nuclear warfare.