Kenneth Waltz (1924–2013) is perhaps the most enduringly influential figure in international relations theory of the second half of the twentieth century. He is considered the father of the structural-realist or neorealist school, and his views on core questions, such as the causes of war and the structure of the international system, are foundational to the field today and likely will remain so for decades to come. Waltz's writings on both theoretical and policy-related topics, from the balance of power to the spread of nuclear weapons, continue to fuel debate. This book is a groundbreaking intellectual biography of Kenneth Waltz, shedding new light on the development and significance of his key contributions. Paul R. Viotti draws on extensive, candid interviews with Waltz as well as Waltz's personal files and archival research to provide a nuanced account of the great scholar's life and thought. He traces the intellectual sources and personal experiences that shaped Waltz's work, including an intense Lutheran upbringing; service in World War II and the Korean War; and the academic environments of Oberlin College, Columbia University, and the University of California, Berkeley. Viotti examines the key influences on Waltz's major works, Man, the State, and War and Theory of International Politics, and analyzes their distinctive insights. Engaging with the views of Waltz's critics and featuring reminiscences from his colleagues, this book is a compelling portrait of an intellectual titan.