Foreign-policy strategy requires harmonizing means and ends, yet during the first two decades of the post–Cold War era, American foreign-policy commentators stopped trying to “define the limit” to America’s overseas ends. The results of this shift are especially troublesome today, as America struggles with reduced means. After years of post-9/11 increases, America’s defense budget is decreasing. There’s also less money for foreign aid. Challengers like China, Russia, and Iran are fighting the enlargement of American power and American-style government. Obama, by withdrawing U.S. troops from Afghanistan and Iraq and resisting military action in Syria and Iran, has tried to better align America’s overseas obligations with its domestic resources. But he’s encountered relentless criticism from hawks who want America to push forward, as hard as possible, on every frontier.