Since the end of the Cold War, America has boosted its military presence in only a single region, the Middle East. The area holds half the world’s oil reserves, sits astride crucial international shipping lanes, and makes up the heartland of Islamic fundamentalist terrorism. It’s almost universally assumed to be central to American foreign policy. But that assumption is wrong, and getting less true with each passing year, argues Philip E. Auerswald, an economist at George Mason University and Harvard’s Kennedy School of Government.