Security Forces practice for Global Strike Challenge
U.S. Air Force Senior Airman Stephen Boyd, 307th Security Forces Squadron, watches the impact of a 40mm practice grenade during training for the Global Strike Challenge, Sept. 5, 2012, Barksdale Air Force Base, La. The GSC is the world's premiere bomber, intercontinental ballistic missile and security forces competition with units participating from Air Force Global Strike Command, Air Combat Command, Air Force Material Command, Air Force Reserve Command and the Air National Guard. (U.S. Air Force photo by Master Sgt. Greg Steele/Released)