The Battle of Khe Sanh was conducted in northwestern Quảng Trị Province, Republic of Vietnam, between 21 January and 9 July 1968 during the Vietnam War. The belligerent parties were elements of the United States III Marine Amphibious Force, 1st Cavalry Division, the U.S. Seventh Air Force, minor elements of the South Vietnamese Army against two to three division-size elements of the North Vietnamese Army. The American command in Saigon initially believed that combat operations around the Khe Sanh Combat Base during the summer of 1967 were just part of a series of minor North Vietnamese offensives in the border regions. That appraisal was altered when it was discovered that NVA was moving major forces into the area during the fall and winter. A build-up of Marine forces took place and actions around Khe Sanh commenced when the Marine base was isolated. During a series of desperate actions that lasted 5 months and 18 days, Khe Sanh Combat Base and the hilltop outposts around it were under constant North Vietnamese ground, artillery, mortar, and rocket attacks. During the battle, a massive aerial bombardment campaign was launched by the U.S. Air Force to support the Marine base. Over 100,000 tons of bombs were dropped until mid April by aircraft of the U.S. Air Force, Navy, and Marines onto the surrounding areas of Khe Sanh. This was roughly 1,300 tons of bombs dropped daily–five tons for every one of the 20,000 NVA soldiers initially estimated to have been committed to the fighting at Khe Sanh. In addition, 158,000 large-caliber shells were delivered on the hills surrounding the base. This expenditure of aerial munitions dwarfs the amount of munitions delivered by artillery, which totals eight shells per NVA soldier believed to have been on the battlefield.