The United States of America has been the most powerful country in the world for the past seventy years, but will Washington’s reign as the world’s leading superpower continue? The U.S. National Security Strategy declares that the return of great power competition with Russia and China is the greatest threat to U.S. national security and economic well-being. Perhaps surprisingly, international relations scholarship does not have much to say about who wins great power rivalries, and many contemporary analysts argue that America’s autocratic rivals will succeed in disrupting or displacing U.S. global leadership. In sharp contrast, this book makes the novel argument that democracies enjoy built-in advantages in international geopolitics. Drawing on the writings of political philosophers—such as Herodotus, Machiavelli, and Montesquieu—and cutting-edge social science research, this book explains the unique economic, diplomatic, and military advantages that democracies bring to the international arena. It then carefully considers the advantages and disadvantages possessed by autocratic great powers. These ideas are then examined in a series of seven case studies of democratic-versus-autocratic rivalries throughout history, from ancient Greece to the Cold War. The book then unpacks the implications of this analysis for the United States, Russia, and China today. It concludes that, despite its many problems, America’s fundamentals are still much better than Russia’s and China’s. By making the “hard-power” argument for democracy, this book provides an innovative way of thinking about power in international politics and provides an optimistic assessment about the future of American global leadership.