For decades, U.S. policy toward the Middle East has revolved around a simple premise: the forward deployment of U.S. military power would deter adversaries — chiefly Iran — and, if necessary, defend host states from attack. Today, that premise is increasingly difficult to sustain. A series of Iranian strikes and threats against critical infrastructure has underscored a widening gap between the promise of protection and the reality of exposure. Far from insulating Persian Gulf states, the U.S. mi...