Following American entry into World War II in December 1941, Hill Field quickly became an important maintenance and supply base, with round-the-clock operations geared to supporting the war effort. Battle-worn warplanes like the A-26, B-17, B-24, B-29, P-40, P-47, P-61, were sent to Hill Field for structural repairs, engine overhauls, and spare parts. The peak wartime employment at Hill Field was reached in 1943 with a total of just over 22,000 military and civilian personnel. Men and women at the depot rehabilitated and returned thousands of warplanes to combat.