World power transitions are rare but perilous moments when hegemonic leadership passes hands. From the ancient struggles between Athens and Sparta to the world wars of the twentieth century, these grand shifts have often been bloody. The passage of leadership from the United Kingdom to the United States, however, stands out as unusually peaceful. Although this story has been told many times, Schake provides a fresh and insightful account that focuses on key moments when American and British elites revised their judgments about each other and their changing geopolitical fortunes. She argues that the transition was peaceful mostly because it unfolded slowly over a century, during which the United States became an empire and the United Kingdom became a democracy. A shared political heritage and common liberal democratic values helped an increasingly beleaguered United Kingdom decide that it could cede leadership to the United States and harness U.S. power to the pursuit of its own interests. The book is most fascinating in its details, illuminating the myriad struggles between London and Washington over the rules and institutions that would form the basis for Pax Americana.