not attack communist forces unless provoked by aggressive action of the communist Viet Cong, or in some cases, by North Vietnamese Army (NVA) ground units in the South. On the night of 2 August 1964 the Gulf of Tonkin incident occurred in which North Vietnamese gunboats directly clashed with United States Navy destroyers. At Clark, the base went on alert and the atmosphere was that of a wartime appearance. Fighter Squadrons were deploying to USAF bases in Thailand, and transports began shipping supplies and equipment to South Vietnamese bases used by the United States. The two B-57 squadrons went on alert and on 5 August the squadrons were notified to deploy 20 B-57Bs of the 8th and 13th BS to Bien Hoa Air Base near Saigon. This would mark the first deployment of jet combat aircraft to Vietnam. However, this was technically a violation of the Geneva Protocols which forbade the introduction of jet combat aircraft to Vietnam. To abide by the Geneva protocols, both squadrons rotated frequently over the next four years first to Bien Hoa AB, then to later Tan Son Nhut AB. In November 1964, both squadrons were transferred from 13th AF control to the 405th Fighter Wing at Clark. Rotations were moved to Da Nang AB in June 1965 to facilitate attacks in Laos and North Vietnam, but high attrition rates over the North led to the movement to Phan Rang AB on the South Central coast in June 1966. Finally, in October 1966 the 35th Tactical Fighter Wing was moved to Phan Rang AB and took over the units on a permanent basis. In late December 1972, the 13th Bombardment Squadron returned to the 405th from the 8th Tactical Fighter Wing at Ubon RTAFB, Thailand with B-57G Canberras, which were B-57B that had been returned to Martin in 1969 and modified as night intruders for use in Vietnam in September 1970 under a project known as Tropic Moon. The B-57s, however were transferred almost immediately back to the United States and assigned to the 190th Bombardment Group (Tactical) of the Kansas Air National Guard at Forbes AFB. The 13th Bomb Squadron remained assigned to the wing as an administrative unit until it was inactivated on 30 September 1973. South Vietnam B-57 program In 1964, the United States secretly agreed to supply a few B-57Bs to the Republic of Vietnam Air Force. The United States had