That attack came on January 21, 1968, when PAVN forces began a massive artillery bombardment of Khe Sanh, hitting the base’s main store of ammunition and destroying 90 percent of its artillery and mortar rounds. President Lyndon Johnson agreed with Westmoreland’s argument that the base should be held at all costs, and U.S. and South Vietnamese forces launched Operation Niagara, a major artillery bombardment of suspected locations of North Vietnamese artillery in the hills surrounding Khe Sanh.
As Westmoreland, President Lyndon B. Johnson and other officials considered Khe Sanh to be the primary target of the North Vietnamese, they largely ignored signs of a Communist buildup in more urban areas of South Vietnam. This proved to be a mistake, as on January 31, 1968–a date celebrated as the lunar new year, or Tet–some 70,000 North Vietnamese and Viet Cong forces launched a coordinated series of fierce attacks on more than 100 cities and towns in South Vietnam. Known as the Tet Offensive, this aggressive operation aimed to break Army of the Republic of Vietnam (ARVN) forces, inspire rebellion among the South Vietnamese population against the regime in Saigon and drive a wedge between South Vietnam and its powerful ally, the United States. Suddenly, the long and bitter struggle at Khe Sanh began to look like a diversionary tactic meant to tie up U.S. and South Vietnamese resources leading up to the Tet Offensive.