U.S. Air Force Chief Master Sgt. Matthew Grengs, 55th Wing command chief, stands at parade rest during the Air Force Birthday retreat ceremony on the parade grounds Sept. 18. Before the Air Force became its own branch of the military, it was a part of the Army. On Aug. 1, 1907, the U.S. Army Signal Corps formed the Aeronautical Division, which later evolved into the Air Force. (U.S. Air Force photo by Charles Haymond)