During the Vietnam War, fighter-bombers played a crucial role in providing close air support to American and South Vietnamese soldiers. The propeller-driven A-l Skyraider was frequently the battlefield choice of commanders who needed fighter-bomber support. Nicknamed the "Spad," the A-1 Skyraider had been operational since 1946, and could deliver up to 8,000 pounds of explosives, including napalm, phosphorus, and cluster bomb units. The A-1 could fire rockets and carry four 20mm cannons that together could fire over 2,000 rounds a minute. Although its maximum air speed was only 318 mph, the A-l could remain airborne over targets much longer than jet aircraft, and it was also highly accurate delivering its bomb loads. During the Korean War, the A-l had been extensively used on naval aircraft carriers, but by the early 1960s the navy was replacing the A-l with the A-4 Skyhawk jet. The A-ls were transferred to the United States Air Force and the Vietnamese Air Force, where they were first employed in Operation Farmgate. By 1968 the A-l Skyraider was the backbone of close air support operations in the Vietnamese Air Force.