'Every 20 years or so—the regularity is a little astonishing—Americans hold a serious debate about their place in the world. What, they ask, is going wrong? And how can it be fixed? The discussion, moreover, almost always starts the same way. Having extricated itself with some success from a costly war, the United States then embraces a scaled-down foreign policy, the better to avoid overcommitment. But when unexpected challenges arise, people start asking whether the new, more limited strategy is robust enough. Politicians and policy makers, scholars and experts, journalists and pundits, the public at large, even representatives of other governments (both friendly and less friendly) all take part in the back-and-forth. They want to know whether America, despite its decision to do less, should go back to doing more—and whether it can.'