But conditions have changed radically since the cold war. When the United States established major bases in West Germany and Japan, they were considered dangerous renegades that needed to be watched. Their reconstructed governments also desired protection, particularly from the Soviet Union and China. NATO’s first secretary general, Hastings Ismay, famously said the alliance existed “to keep the Russians out, the Americans in, and the Germans down.”

Today, our largest permanent bases are still in Germany and Japan, which are perfectly capable of defending themselves and should be trusted to help their neighbors. It’s time they foot more of the bill or operate their own bases. China’s authoritarian capitalism hasn’t translated into territorial aggression, while Russia no longer commands central and eastern Europe. That the military brass still talk of maintaining the capacity to fight a two-front war — presumably on land in Europe, and at sea in the Pacific — speaks to the irrational endurance of the Truman Doctrine.

Our wars in the Middle East since 2001 doubled down on that costly, outdated doctrine. The domino theory behind the Vietnam War revived under a new formulation: but for the American umpire, the bad guys (Al Qaeda, Iran, North Korea) will win.

Despite his supporters’ expectations, President Obama has followed a Middle East policy nearly identical to his predecessor’s. He took us out of Iraq, only to deepen our commitment to Afghanistan, from which we are just now pulling out. He rejected the most odious counterterrorism techniques of George W. Bush’s administration, but otherwise did not change basic policies. Mr. Obama’s gestures toward multilateralism were not matched by a commensurate commitment from many of our allies.

Cynics assert that the “military-industrial complex” Dwight D. Eisenhower presciently warned against has primarily existed to enrich and empower a grasping, imperialist nation. But America was prosperous long before it was a superpower; by 1890, decades before the two world wars, it was already the world’s largest and richest economy. We do not need a large military to be rich. Quite the opposite: it drains our resources.

Realists contend that if we quit defending access to the world’s natural resources — read, oil — nobody else would. Really? It’s not likely that the Europeans, who depend on energy imports far more than the nation that owns Texas and Alaska would throw up their hands and bury their heads in the sand. It’s patronizing and naïve to think that America is the only truly “necessary” country. Good leaders develop new leaders. The Libyan crisis showed that our allies can do a lot.