In this impressive study, Legro argues that major strategic turning points are not simply the result of shifts in power and interests; they also involve the interplay of "collective ideas" within states about how to relate to the outside world. Legro explores many of the most important cases: the United States' turn to internationalism after World War II, Japan's decision in the 1860s to join the great powers, Germany's failed reintegration into Europe after World War I, Gorbachev's late-Soviet "new thinking." In each instance, shocks to old thinking -- typically war or economic calamity -- make possible a reorientation of foreign policy. And it is at these historical "pivot points," when the nation's interests are not clear and leaders are forced to puzzle about the future, that ideas and beliefs matter. The causal connections between power, interests, and collective ideas are not always clear, but Legro makes a compelling case that strategic beliefs cannot be reduced to strategic circumstance. He ends by reflecting on the future of the Bush "revolution" and argues that, absent further terrorist attacks, U.S. foreign policy is likely to tack back to the post-World War II mainstream.