The Douglas B-26 Invader was involved in the fighting in Vietnam for nearly twenty years, from 1951 when they were used by the French, until 1969 when the last aircraft in American service were withdrawn.
The first aircraft to go to Vietnam were five RB-26s and twenty four B-26s provided to the French during 1951. These aircraft were taken by aircraft carrier to Hawaii and then flown to the French at Tourane, and were followed by another nine that flew directly from the United States. The supply of surplus B-26s then dried up as they became increasingly in demand for service on Korea, and the aircraft didn't reach the French until 1954, when sixteen B-26s from the Far East Asian Air Forces were loaned to the French, before being replaced by sixteen normal bombers and three more RB-26s under the Mutual Defence Assistance Program. A final batch of twenty five B-26s were provided before the end of 1951.
The French used their aircraft to drop Lazy Dog finned bullets against Viet Minh anti aircraft guns, but they were unable to save the garrison at Dien Bien Phu, and the French use of the B-26 ended in May 1954. The Geneva Accords, which ended the French involvement in Vietnam included a provision banning the introduction of jet powered combat aircraft in the area.
This provision played a part in the reappearance of the B-26 in the skies over Vietnam towards the end of 1961. It was one of a number of piston driven aircraft used to equip the new 4400th Combat Crew Training Squadron, which was created at Elgin Air Force Base Florida as the first step towards creating a counterinsurgency force.
In late December 1961 four RB-26s from the 4400th were amongst the first American combat aircraft to go to Vietnam, under the Farm Gate program. In theory these aircraft were to be used to train South Vietnamese Air Force crews, but in fact they were used in combat by their American crews, something that became public knowledge when on 3 February 1963 one aircraft was shot down, with the loss of Captains John F. Shaughnessy Jr and John P. Bartley. The Farm Gate program became the First Air Commando Squadron on 8 July 1963, by which time it had 10 B-26s and 2 RB-26s at Bien Hoa and eight B-26s on detachment at Soc Trang and Pleiku.
Problems soon developed with the increasingly elderly B-26s. During 1963 two aircraft were lost when their wings failed, and the cause was eventually traced to failure of their wing spars. In the spring of 1964 the basic B-26 Invader was withdrawn from service.
Two years earlier the Air Force had asked On Mark Engineering to produce an updated version of the B-26, with the designation B-26K. When these aircraft appeared they had reinforced wings, more powerful engines, and eight hard points under the wings which could be used to carry 8,000lb of ordnance, doubling the payload of the B-26. These rebuilt aircraft were used to equip the 609th Special Operations Squadron, which operated them from Nakhom Phanom Air Base in Thailand. This eventually forced a final change of designation, when the Thai government objected to the use of bombers from their air bases. The Air Force responded by re-designating the B-26K and the A-26A, apparently to the satisfaction of the Thais.
The B-26K/ A-26A was used against he Ho Chi Minh trail, often repeating the night attacks carried out with some success by the B-26 in Korea. Operations began in 1966 and continued until November 1969, when a combination of losses and a shortage of spare parts forced the Air Force to withdraw the remaining aircraft from combat, ending a service career than had lasted for 24 years.