south of the DMZ. The artillery unit was moved to Ca Lu to cover Route 9 and on 1 May the 1/1 Marines completed the march from the base to Cam Lộ encountering no PAVN. In December 1966, Special Forces Detachment A-101 moved from Khe Sanh to a site near the village of Lang Vei, Fighting began at Khe Sanh in late April 1967 with the hill fights, which later expanded into the 1968 Battle of Khe Sanh. U.S. commanders hoped that the PAVN would attempt to repeat their famous victory at the Battle of Dien Bien Phu, which would permit the U.S. to wield enormous air power. Boeing B-52 Stratofortresses alone dropped more than 75,000 tons of bombs on the PAVN 304th and 325th Divisions encroaching the combat base in trenches. On April 1, 1968, the U.S. Army's 1st Cavalry Division launched Operation Niagara to break the siege of the base. All three brigades from the 1st Cavalry participated in this vast airmobile operation, along with a Marine armor thrust. The defense of Khe Sanh commanded international attention and was considered the climactic phase of the Tet Offensive. On July 5, 1968, the combat base was abandoned, the U.S. Army citing the vulnerability of the base to dug-in enemy artillery positions in neutral Laos and the arrival of significant airmobile forces in I Corps (1st Cavalry and 101st Airborne divisions). However, the closure permitted the 3rd Marine Division to conduct mobile operations along the DMZ. In 1971, Khe Sanh was reactivated by the U.S. Army (Operation Dewey Canyon II) to support Operation Lam Son 719, the South Vietnamese invasion of Laos. On the night of 23 March a PAVN sapper attack on Khe Sanh resulted in 3 Americans killed and several aircraft and 2 ammunition dumps destroyed, PAVN losses were 14 killed and 1 captured. The base was abandoned again on 6 April 1971. On 27 January 1972 a U.S. Air Force Lockheed AC-130 gunship was shot down by a PAVN SA-2 missile over the base. In March 1973, American intelligence reported that the PAVN had rebuilt the airstrip at Khe Sanh and were using it for courier flights into the South. Tourism Khe Sanh Combat Base can be visited daily as part of tours starting in Huế. Since its abandonment, most of the base has become overgrown by wilderness or coffee and banana plants. A small museum on