An ambitious look at how the twentieth century’s great powers devised their military strategies and what their implications mean for military competition between the United States and China   How will the United States and China evolve militarily in the years ahead? Many experts believe the answer to this question is largely unknowable. But Zack Cooper argues that the American and Chinese militaries are following a well-trodden path. For centuries, the world’s most powerful militaries have adhered to a remarkably consistent pattern of behavior, determined largely by their leaders’ perceptions of relative power shifts. By uncovering these trends, this book places the evolving military competition between the United States and China in historical context.   Drawing on a decade of research and on his experience at the White House and the Pentagon, Cooper outlines a novel explanation for how militaries change as they rise and decline. Tides of Fortune examines the paths of six great powers of the twentieth century, tracking how national leaders adjusted their defense objectives, strategies, and investments in response to perceived shifts in relative power. All these militaries followed a common pattern, and their experiences shed new light on both China’s recent military modernization and America’s potential responses.