Airmen from the 13th Air Support Operations Squadron at Fort Carson, Colo., cross the Arlington National Bridge en route to Arlington National Cemetery, Va., to honor a fallen comrade Maj. David Gray by completing the "DG 140” Aug. 8, 2013. The DG 140 is a 140-mile memorial ruck march for Gray, that began at the Casualty Reception Center at Dover Air Force Base, Del., to Gray's headstone at Arlington National Cemetery Aug. 4 - 8. Gray was killed in action in Afghanistan and was posthumously awarded the Bronze Star Medal and Purple Heart. (U.S. Air Force photo/Senior Airman Carlin Leslie)