Khe Sanh and its 6,000 U.S. Marine Corps, Army and ARVN defenders was surrounded by two to three PAVN divisions, totaling approximately 20,000 men. Throughout the siege, which lasted until 8 April, the allies were subjected to heavy mortar, rocket, and artillery bombardment, combined with sporadic small-scale infantry attacks on outlying positions. With the exception of the overrunning of the U.S. Special Forces camp at Lang Vei, however, there was never a major ground assault on the base and the battle became largely a duel between American and North Vietnamese artillerists, combined with massive air strikes conducted by U.S. aircraft. By the end of the siege, U.S. Air Force, Marine Corps, and Navy aircraft had dropped 39,179 tons of ordnance in the defense of the base.