arrived 24 hours a day. On 22 March the 318th Fighter Interceptor Squadron deployed to Osan AB from McChord AFB, Washington. This marked the first time in history that Aerospace Defense Command (ADC) F-106 fighter interceptors had flown to a critical overseas area, using in-flight refueling along with tactical air units. Although the Pueblo crisis subsided with the crew's release on December 23, 1968, fighter unit deployments occurred on a regular basis. On April 15, 1969, the North Koreans again triggered a period of tension when it shot down a U.S. Navy EC-121 Warning Star flying in international airspace over the Sea of Japan. F-106s from the 95th Fighter Interceptor Squadron, deployed to Osan AB from 15 November 1969 – 1 May 1970. Attached to Fifth Air Force ADVON, 15 November 1969 – 1 May 1970. The response by the U.S. resulted in another increase of fighter forces on the peninsula, and eventually set the stage for return of permanently assigned fighter units to South Korea. Vietnam War Throughout this period, the U.S. Air Force was deeply committed to the Vietnam War. At Osan, the major USAF units were 6145th Air Force Advisory Group acting as a training/logistical support unit to the ROKAF; the 314th Air Division; and the 6314th Support Wing. The 611th Military Airlift Command Support Squadron (611th MASS) at Kimpo Air Base would later move to Osan. However, as the U.S. withdrew incrementally from South Vietnam and Thailand, Pacific Air Forces repositioned its force structure which led to substantial changes for the USAF in South Korea. On March 15, 1971, the 3rd Tactical Fighter Wing was activated at Kunsan AB. At Osan AB, PACAF activated the 51st Air Base Wing to assume host-unit responsibilities at Osan AB on November 1, 1971. Two weeks later, on November 13, 1971, the 3rd TFW's 36th Tactical Fighter Squadron moved to Osan AB. Total withdrawal of U.S. forces from South Vietnam by March 1973 resulted in another important change for Osan AB. On September 30, 1974, the 51st ABW was redesignated as the 51st Composite Wing (Tactical), and assigned the 36th TFS with its F-4D/E Phantom IIs and the 19th Tactical Air Support Squadron with its OV-10As. 1970s/1980s With Osan AB serving as the nucleus for more than 20 USAF activities in South Korea, it experienced a period of facility and infrastructure changes during the 1970s. Although many of the Korean