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tical integrity of the required ground units.18 The amount of warning time was yet another unknown factor in the equation to determine what sized force could be used. General Vogt knew he would have to conduct the evacuation on short notice, regardless of other commitments. With sufficient warning time, i.e., 24 hours or more, other forces would also be available, but in the spring of 1973 there was little promise of a day's warning.
USSAG planners recognized that the nearest infantry units capable of serving as security forces were III MAF Marines stationed on Okinawa. Given sufficient warning time, units from Okinawa could be airlifted to Thailand. In the event of insufficient warning time, Seventh Air Force security forces would have to suffice despite the fact that USSAG planners considered this a high-risk, last-resort option.
Helicopter availability loomed as the largest unanswered question confronting the planners. The Seventh Air Force had some helicopters in Southeast Asia as did the Marine Corps, but the distances involved dictated the use of heavy helicopters. The medium load CH-46 helicopters did not possess the required capacity nor the range to complete this mission successfully. Only a heavy helicopter could carry enough fuel for the extended distance and still have room to carry the payload. At this time, in early 1973, all of the Marine Corps' heavy lift helicopters were committed to Operation End Sweep, minesweeping operations in Haiphong Harbor. Consequently, USSAG envisioned for its initial concept of operations the use of Air rbrce helicopters and, time permitting, Marine security forces located on Okinawa.19
The Seventh Air Force's 21st Special Operations Squadron (21st SOS), equipped with CH-53 aircraft, and the 40th Aerospace Rescue and Recovery Squadron (40th ARRS), equipped with HH-53s, would provide the airlift support. Basically identical helicopters, the HH-53 differed from the CH-53 in that a rescue hoist, jettisonable auxiliary fuel tanks, and a refueling probe had been added to enable the HH-53 to conduct its mission of search and rescue. In the spring of 1973, combat veterans manned both squadrons, but with the passage of time many of these airmen were replaced by less experienced pilots.20
The antiaircraft capabilities of the Khmer Communists posed a serious threat to all aircraft, especially the helicopters. Similiarly, the American security forces once in their assigned zones could be subjected to Communist artillery and mortar fire. With these factors in mind, a detailed air support plan was developed along with stringent rules of engagement.21
Operational control of the forces committed to the evacuation rested with General Vogt, USSAG Commander, but would be exercised through a mission commander in a specially equipped C-130 airborne battle command and control center (ABCCC), which would orbit at some distance from Phnom Penh. Meanwhile control of tactical aircraft operating over the landing zones and along the helicopter approach and retirement routes would be handled by the tactical air coordinator airborne, TAC(A), in an OV-10 aircraft. Control of the helicopters was assigned to a separate helicopter direction center (HDC) in an additional C-130. The Seventh Air Force had enough planes to relieve this aircraft on station, thereby providing continuous round-the-clock control of the operation. The commander of the landing zone/security forces also would come under the Commanding General, USSAG, via communications with the orbiting ABCCC.22
With each passing week during the spring of 1973, the number of potential evacuees grew. The original estimate of 200 to 300 increased to 600-700 by the end of May 1973, a phenomenon directly related to the success of the Khmer Rouge offensive. Noting this, USSAG increased the number of landing zones, which in turn necessitated an enlargement of the security force. In June, III MAF received orders to provide a second reinforced rifle company and a command group to support the operation. This responsibility fell to the 3d Marine Division. From June 1973 until execution of the operation, a battalion of the division always had two companies on call for Operation Eagle Pull. The command group operated independently, preparing for every conceivable eventuality, but sometimes events overcame plans as they did in 1973.23
In July, without warning. General Vogt received a message from CinCPac to execute Operation Eagle Pull. As Major Baker was increduously absorbing the text of the message in preparation for placing the evacuation plan into effect, he received a phone call from the CinCPac Command Center, "Disregard the message!" The staff at CinCPac had been so sure that the evacuation would take place that they had prepared an "execute" message and, inexplicably, it had been released. A further touch of irony was added by the coincidental presence of the CinCPac action officer in Thailand. He had arrived at USSAG Headquarters to attend a previously scheduled planning conference
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