This book of essays by the a leading figure in the new generation of American IR theorists explores the theoretical, historical, and foreign policy implications of American power and postwar order. The first part of the book focuses on the origins and foundational logic of America's post-war order-building project -- advancing ideas about `liberal hegemony' and `constitutional order'. The second part reflects on its evolving character and fate in the aftermath of the Cold War, the rise of unipolarity, and the post-9/11 threat of global terrorism. In this unique study of a superpower, Ikenberry argues that though the American world order is now in upheaval, in the end, the United States still has powerful incentive to sponsor and operate within a liberal rules-based system.