An armorer of the 15th U.S. Air Force checks ammunition belts of the .50 caliber machine guns in the wings of a P-51 Mustang fighter plane before it leaves an Italian base for a mission against German military targets. The 15th Air Force was organized for long-range assault missions and its fighters and bombers ranged over enemy targets in occupied and satellite nations as well as Germany itself. Ca. September 1944. (National Archives photo no. 208-MO-18H-32984) Source: U.S. Air Force .