WASHINGTON (Reuters) - The U.S. military began deploying anti-aircraft missiles at the Pentagon and bases around Washington on Monday for an exercise to test a multi-layered defense of the national capital region, defense officials said. "Avenger" anti-aircraft systems -- heat-seeking Stinger missiles on wheeled Humvee military jeeps -- will be stationed at the bases for at least four days beginning on Tuesday, including Wednesday's anniversary of Sept. 11 hijack airliner attacks on America. The officials, who asked not to be identified, told Reuters the "Clear Skies 2" exercise did not call for missiles to carry live warheads. The exercise, similar...