U.S. citizens and local nationals were evacuated by helicopter from Phnom Penh, Cambodia, during Operation Eagle Pull, which occurred 50 years ago, April 12, 1975.
The operation became necessary as the communist military group Khmer Rouge surrounded the capital of Phnom Penh to overthrow the U.S.-backed Khmer Republic government.
Planning for the evacuation started months earlier. On Jan. 6, 1975, the 31st Marine Amphibious Unit, part of the amphibious ready group, was alerted to sail to the Gulf of Thailand near Cambodia to prepare for an evacuation. Three months later, on April 3, 1975, U.S. Ambassador to Cambodia John Gunther Dean requested the deployment of an Operation Eagle Pull command element, which landed at Pochentong International Airport near Phnom Penh. The command element supervised the fixed-wing aircraft evacuation of more than 750 Cambodians over the next seven days.
By April 10, 1975, artillery and rocket fire directed at the airport by the Khmer Rouge became so intense that the fix-wing evacuation was stopped.
As a final option, the command group selected a soccer field close to the U.S. Embassy as a helicopter landing zone for further evacuation.
The embassy staff prepared to leave April 11, 1975, but the evacuation was delayed a day, allowing the USS Hancock, a World War II-era aircraft carrier, to join the evacuation fleet.
In addition to the Hancock, the fleet consisted of the amphibious assault ship USS Okinawa, which carried CH-46 Sea Knight, CH-53 Sea Stallion, AH-1J Sea Cobra and UH-1E Iroquois helicopters; the amphibious transport dock ship USS Vancouver; and the dock landing ship USS Thomaston.
The destroyer USS Edson, the guided missile destroyer USS Henry B. Wilson, the destroyer escorts USS Knox and USS Kirk, and the frigate USS Cook provided escort and naval gunfire support.
At 6 a.m., April 12, 1975, helicopters began launching from the USS Okinawa and USS Vancouver, with a security force of 360 Marines.
Around 8:45 a.m., the first wave of helicopters made it to the landing zone, where Marines established perimeter security and began evacuating 84 Americans, 205 Cambodians and other foreign nationals.
The U.S. Embassy was shuttered by 9:45 a.m., and at 11:15 a.m., the combat control team and Eagle Pull command element were safely extracted.
The last Marine helicopter landed on the USS Okinawa at 12:15 a.m.
On April 13, 1975, the evacuees were flown to U-Tapao Air Base in Thailand, and the amphibious ready group set sail to the South China Sea to participate in the Saigon, South Vietnam evacuation, which occurred at the end of the month. 
Eagle Pull was a tactical success because everyone evacuated made it safely out. However, it was not considered a political strategic success because the U.S.-backed government would soon fall.
On April 18, 1975, the Khmer Rouge occupied Phnom Penh and soon after began executing perceived political opponents and minority groups, resulting in the deaths of up to 2 million people, which was about 25% of Cambodia's population.
The U.S. Embassy in Cambodia reopened, and normal relations resumed in May 1994.
With the passage of the 1971 Cooper-Church Amendment, which cut off funding for U.S. military operations in Laos and Cambodia, it was only a matter of time before the Khmer Rouge took over Cambodia, according to Sydney H. Batchelder and D.A. Quinlan, authors of "Operation Eagle Pull," a May 1976 article published in the Marine Corps Gazette magazine.
This amendment to the Foreign Assistance Act of 1970 was named for Senators John Cooper and Frank Church, who sponsored it.
Eagle Pull was an early example of noncombatant evacuation operations, or NEOs, by helicopter. The Marine Corps and the other services participated in many subsequent NEOs around the globe, using a blueprint similar to Eagle Pull. Some were considered successful, and others less so.
Eagle Pull also demonstrated the utility of an amphibious ready group in operations, both military and humanitarian.