The CH-54A heavy helicopters in Vietnam were mainly used for transport and occasionally for carrying the M-121 high explosive bombs. These bombs were modified with an extended nose fuze to detonate about 3 feet above the ground, effectively clearing forests for helicopter landing sites. One notable operation involved a CH-54A helicopter from Phu Bai Air Base, also known as Camp Hochmuth, in central Vietnam. The US Armed Forces started operating this base in 1963, initially as a communications radio station. The base later hosted US Marines, paratroopers, and special operations forces, and an airstrip was built using M8A1 steel airfield plates. At one point, the airfield also accommodated US Marine Corps aircraft and helicopters. Despite frequent attacks by the Viet Cong, the Phu Bai base remained operational by the US military until the end of 1972.