U.S. Air Force Senior Airman Yu Yuan, left, material management technician with the 227th Air Support Operations Squadron (ASOS), prepares to receive an M67 high explosive frag hand grenade from Senior Airman Ryan Muller, Tactical Air Control Party specialist with the 227th ASOS, during Operation Kriegshammer training at Grafenwoehr Training Area, Germany on July 14, 2014. (U.S. Air National Guard photo by Master Sgt. Andrew J. Moseley/Released)