 Other reinforcements consisted of the 21st Division which was plagued by a very slow move from the Delta area in the south of the country and cleared QL-13 after protracted fighting.The ARVN defenders did have one card to play throughout the battle, the immense power of U.S. air support.The use of B-52 Stratofortress bombers (capable of carrying 108 MK82 (500 pound) bombs on one run) in a close support tactical role, as well as AC-119 Stinger and AC-130E Spectre gunships, fixed wing cargo aircraft of varying sizes, AH-1 Cobra attack helicopters and Republic of Vietnam Air Force (RVNAF) A-37s.