In the second half of the twentieth century, the United States engaged in the most ambitious and far-reaching liberal order building the world had yet seen. But in the last decade, the American-led order has been troubled. G. John Ikenberry, author of Liberal Leviathan: The Origins, Crisis, and Transformation of the American World Order, argues that the crisis that besets the American-led order is a crisis of authority. The forces that have triggered this crisis have resulted from the successful functioning and expansion of the postwar liberal order, not its breakdown. The liberal international order has encountered crises in the past and evolved as a result. It will do so again.