WHAT DOES MODERN HISTORY have to teach us about the age of American empire? The final chapters of the British Empire offer lessons and parallels aplenty. Empires don’t last forever, and the combination of martial victory, popular ennui, and liberal anti-patriotism is a dangerous mix for a superpower.

At the beginning of the 20th century, the British Empire was an unopposed hyperpower (much as the United States has been since 1989). As historian Colin Cross observes: “In terms of influence it was the only world power.” The British people and their leaders accepted this fact. In the early 1930s, Prime Minister Stanley Baldwin pronounced that “the British Empire stands firm, as a great force for good.” Historian William Manchester argues that “most of the crown’s subjects, abroad as well as at home, felt comfortable with imperialism.”