The USSAG commander, Air Force Lt. Gen. John J. Bums, was responsible not only for the residual support and advisory functions in Vietnam - a responsibility his headquarters had inherited from USMACV-but also for American air forces in Thailand, which fell under his control as Commander 7th Air Force, giving him the title of COMUSSAG/7AF. Included in those forces were two USAF helicopter squadrons at Nakhon Phanom, the 21st Special Operations Squadron (21st SOS) and the 40th Aerospace Rescue and Recovery Squadron (40thARRS), which had been retained in Southeast Asia in Part to evacuate American personnel and friendly foreign nationals from Phnom Penh should a Khymer Rouge victory become imminent. An evacuation plan had been drawn up, under the code name EAGLE PULL, which envisaged a variety of options, depending on how much warning was given and how many evacuees were anticipated. When the Khymer Rouge dry-season offensive broke on New Year's Day, it quickly became apparent that the battered and demoralized Lon Nol forces, operating on a logistical shoestring and hampered by widespread corruption among the officer corps, were nearing the end of their tether. Though the Lon Nol forces were able to contain an initial penetration of the perimeter around Phnom Penh, the Khymer Rouge captured several key positions along the Mekong to the south and began interdicting the river supply convoys from Saigon which were Phnom Penh's primary source of supply. After a series of increasingly bloody attempts to fight the convoys through, the American authorities gave up. The last ship reached Phnom Penh on 23 January and the capital was now totally dependent on resupply by air. Since Congress had forbidden the use of U.S. military personnel in Cambodia, this was carried out by contract carriers, some of them using C-130 transports on loan from the Air Force.
In late February, a small Congressional delegation led by Rep. John Flynt of Georgia visited Saigon at President Ford's request-a request made in the hope that the delegation would recommend additional funding for theThieu and Lon Nol governments. A quick side trip to Phnom Penh left the delegates appalled by the conditions in the refugee camps there-some 2.7 million Cambodians out of a total population of under eight million had taken refuge there to escape the ravages of war and the Khymer Rouge - and they returned with the recommendation that at least some funds for humanitarian aid be restored. Events made their recommendation irrelevant before Congress could act.
In the meantime, the American ambassador, John Gunther Dean, had begun moving non-essential Americans and those Cambodians who might be at risk in the event of a communist takeover out of country. The evacuation at first proceeded via commercial flights from Pochentong Airport, but then shifted to contract flights. As the ring around Phnom Penh tightened, Dean issued the alert for EAGLE PULL. By the second week of April, as Khymer Rouge rocket attacks threatened to closedown Pochentong, a Navy task force was standing by in the Gulf of Slam with two carrier-based Marine helicopter squadrons, HMM 462 and HMM 463, embarked. Dean ordered EAGLE PULL to be executed on 12 April, and at 10:00 hours watched as his security detachment lowered the embassy flag; within minutes he was aboard a Marine CH-53A on a nearby soccer field. Launched with ample warning and controlled by a small Marine command group and an Air Force Combat Control Team flown in by the 40th ARRS from Thailand, EAGLE PULL had gone like clockwork.