Udorn’s secret history began before the US Air Force arrived. On 11 September 1955 Civil Air Transport, the airline the CIA owned, brought three C-46 transports to the new field. Under its later name, Air America, the company made Udorn its Asian headquarters, and from here its aircraft flew into Laos.

Wikipedia records that Air America continued operations from Udorn into Laos until 3 June 1974, when the ceasefire in Laos ended them. After the fall of Saigon in 1975 the company tried to keep a presence at Udon Thani; that attempt fell through, and Air America was dissolved on 30 June 1976. The numbers of its aircraft and staff at Udorn were not published in the sources reached.

The 432nd Tactical Reconnaissance Wing was activated at Udorn on 18 September 1966. Its first job was photography: the 20th Tactical Reconnaissance Squadron with RF-101C Voodoos until November 1967, the 11th TRS with RF-4Cs from October 1966 to November 1970, and the 14th TRS with RF-4Cs from October 1967 until 30 June 1975.

Unusually, the wing also had fighters. The 13th Tactical Fighter Squadron came in October 1967 and the 555th, the "Triple Nickel", on 28 May 1968 from Ubon, both flying F-4 Phantoms. When North Vietnam invaded the South in spring 1972, Udorn took in more F-4 squadrons for Operation Linebacker: the 523rd, 58th, 308th and 307th TFS and a detachment of the 414th Fighter Weapons Squadron between May and October 1972, and the 421st TFS from 31 October 1972 until the end. The base also housed the 7th Airborne Command and Control Squadron’s C-130 command posts from October 1968 until 30 April 1972, and the 4th Special Operations Squadron from October 1972. Wikipedia credits the 432nd with 36 confirmed aerial victories between 17 December 1967 and 8 January 1973.

The best-known of those victories belong to one crew. Capt. Richard Stephen "Steve" Ritchie of the 555th TFS, flying with his weapons systems officer Capt. Charles B. DeBellevue on four of the five, shot down MiG-21s on 10 May, 31 May, twice on 8 July and on 28 August 1972, every one with an AIM-7 Sparrow. The fifth made him the first US Air Force ace of the war, and he received the Air Force Cross for the action of 28 August.

Two of his kills, the first and the fifth, were flown in F-4D 66-7463. Wikipedia credits the Triple Nickel with 39 victories in the war in all: ten MiG-17s, three MiG-19s and 26 MiG-21s, and with producing the first and second USAF aces of the war. Its unofficial motto was "World’s Largest Distributor of MiG Parts". The squadron left Udorn on 5 July 1974.

Udorn was not safe behind the lines. On 26 July 1968 a team of 25 or more infiltrators with automatic weapons attacked the base, badly damaging a C-141 and an F-4D; a Thai security guard and the C-141’s crew chief were killed, according to Wikipedia. On 10 April 1970 a battle-damaged RF-4C crash-landed on the base, destroyed nine officers’ quarters and killed nine people on the ground. On 3 October 1972 seven guerrillas tried again; three were killed and one captured, and one Thai guard died.

The Americans left after the war. The 432nd was inactivated on 23 December 1975 and the last USAF personnel departed in January 1976. Wikipedia also reports, on the basis of press accounts, that a CIA detention site used in 2002 was located near Udorn; the Thai government denies that such a site existed and the US government has neither confirmed nor denied its location.

Since then Udorn has been Wing 23’s base. Its 231 Squadron flies the Alpha Jets bought from Germany in 1999 to replace the OV-10 Bronco on border patrol, and in 2007 the Cope Tiger exercise was extended from Korat to Udorn.