Battle of Khe Sanh occurred between January 21 and July 9, 1968 and was a part of the Viet Cong Tet Offensive. It resulted in a massive aerial bombardment campaign by the U. S. Air Force (Operation Niagara). It involved more than 6000 Marines holding off more than 20,000 Viet Cong. American casualties included 274 dead and 2,541 wounded. The relief effort to reach Khe Sanh was known as Operation Pegasus (April 1-14, 1968) and resulted in another 703 American deaths and 2,642 wounded.