What happened at the fall of Phnom Penh?
On 17 April 1975, after a siege that began with the Khmer Rouge offensive of 1 January, Khmer Rouge forces entered Phnom Penh, the capital of the US-backed Khmer Republic, and ended Cambodia's five-year civil war. Many residents first greeted them with relief. Within hours the new rulers ordered the whole population out of the city, at least two million people by the finding of the Khmer Rouge tribunal, emptying even the hospitals. It was the first act of a regime under which, by the estimate of Yale's Cambodian Genocide Program and the Documentation Center of Cambodia, about 1.7 million people died.1
Most cities that fall in war are occupied. Phnom Penh was emptied. On the day the Khmer Rouge marched in, they told its people to leave for a few days; the promise was never kept. The evacuation of the capital became the opening act of one of the deadliest regimes of the twentieth century, and the court set up decades later to try its leaders ruled that it was a crime against humanity.2
Background: a republic at war
Cambodia's civil war began after General Lon Nol overthrew Prince Norodom Sihanouk in March 1970. Lon Nol's Khmer Republic, backed by the United States, fought communist insurgents known as the Khmer Rouge, who grew stronger as the war spread across the countryside. The Paris agreements of January 1973 ended American combat in Vietnam but not the war in Cambodia, where the fighting went on, and by early 1975 the Khmer Rouge held almost all of the country except the capital and a few towns.3 › Operation Menu, 1969
Phnom Penh had swollen with people fleeing the war. By the account of the Library of Congress country study, its population had reached some 2.5 million, as many as 1.5 million of them wartime refugees living with relatives or in shantytowns; Cambodgemag speaks of two million inhabitants. The city could not feed itself and lived on what came up the Mekong River from South Vietnam.4
Armies and commanders
On one side stood the Khmer Republic and its army. Lon Nol was president until 1 April 1975, when he resigned and left the country; Saukam Khoy became acting president and Long Boret remained prime minister. The United States was represented by its ambassador, John Gunther Dean, and supplied the city by air.5
On the other side was the Communist Party of Kampuchea, its army and its hidden leadership, the “Angkar”, headed by Pol Pot; among his closest associates were Nuon Chea and Khieu Samphan, who would face trial for that April decades later. The troops who took Phnom Penh were mostly young men in black, with the checked scarves that had become the uniform of the movement.6
The siege in phases
The river closes. The Khmer Rouge opened their dry-season offensive against the capital on 1 January 1975. They held both banks of the Mekong below the city and mined the channel. In late January, by the Naval History and Heritage Command's count, only seven ships of a 16-ship convoy survived the 62-mile run from the border, and in early February convoys struck mines. By 17 February the government had given up trying to reopen the river.7
The airlift. With the river cut, Phnom Penh depended on an American airlift of rice, fuel and ammunition into Pochentong airport. The airfield came under rocket and artillery fire, and every flight grew more dangerous.8
The last weeks. On 1 April Lon Nol resigned and flew out. Last-minute attempts to reach a settlement, through Sihanouk and through Beijing, came to nothing.9
Eagle Pull. On 12 April the United States evacuated its embassy. Marine helicopters from the USS Okinawa and USS Hancock in the Gulf of Thailand landed a security force on a soccer field near the embassy and flew out the ambassador, his staff, the acting president and other Cambodians and foreigners. The counts differ: President Ford reported to Congress 276 people, 82 Americans, 159 Cambodians and 35 others; the Marine Corps history gives 287 and the Navy's 289. The first helicopters landed before nine in the morning, the evacuees were all out by about a quarter to eleven, and rockets began to fall near the landing zone just as the last Marines lifted out at 10:59.10
Ambassador Dean invited the leaders of the republic to leave with him. Several refused, among them the former prime minister Sirik Matak and the prime minister, Long Boret; Saukam Khoy left without telling his colleagues. Both Sirik Matak and Long Boret were executed within weeks of the fall of the city.11
Turning point: 17 April and the order to leave
On the morning of 17 April 1975 the Khmer Rouge marched into Phnom Penh. Many residents came out to greet them, hoping the war was over. The mood turned quickly: the grim, unsmiling young soldiers made it plain that for them the war was not over.12
The evacuation began at once. Soldiers and loudspeakers told the residents that they had to leave and would be away only two or three days, and some were told that the city was in danger of American bombing. There were no exceptions. The hospitals were emptied, and even gravely ill and wounded patients were driven into the streets. People who refused or did not move fast enough were killed.13
The tribunal later found that at least two million people were forced out of Phnom Penh in terrifying and violent circumstances and without warning, and that people were killed or died on the way because of the conditions imposed on them. How many died on the roads is not known: Khieu Samphan himself put the toll at 2,000 to 3,000, a figure the Library of Congress study calls probably an understatement, and Cambodgemag writes of thousands dead from exhaustion, hunger and violence.14
Why the city was emptied is still debated. The Library of Congress study notes the reasons the Khmer Rouge gave, the threat of American air strikes and the difficulty of feeding the cities, and the deeper aims it saw behind them: to turn Cambodia into a nation of peasants, to break up supposed enemy networks in the towns and to take control of the population. Youk Chhang of the Documentation Center of Cambodia calls the evacuation a calculated move to secure the regime's absolute control.15
Aftermath
The regime hunted down the servants of the old one. It seized and executed as many civil servants, police and officers of the Khmer Republic as it could find, and evacuees with links to the government had to pass themselves off as peasants or workers to survive.16
Foreigners and some Cambodians took refuge in the French embassy. Within days the Khmer Rouge demanded the surrender of the Cambodian leaders sheltering there, Sirik Matak among them, and at the end of the month the foreigners were taken by truck to the Thai border.17
The townspeople, now called “new people”, were put to forced labor in the countryside. The Khmer Rouge proclaimed a new beginning, Year Zero, and the regime lasted until the Vietnamese invasion of January 1979. Estimates of its victims differ: about 1.7 million by the count of Yale's Cambodian Genocide Program, some 21 percent of the population, and of the Documentation Center of Cambodia; almost two million according to the United States Holocaust Memorial Museum; well over two million according to the Holocaust Memorial Day Trust. The share of the population they represent is also put differently, 21 percent by Yale and about a third by the Holocaust Memorial Museum.18
Legacy and memory
The evacuation of Phnom Penh stood at the center of the first trial of the regime's surviving leaders. In 2014 the Extraordinary Chambers in the Courts of Cambodia, a court set up by Cambodia with the United Nations, convicted Nuon Chea and Khieu Samphan of crimes against humanity and sentenced them to life imprisonment, and in 2016 the appeals chamber upheld their convictions for murder, political persecution and other inhumane acts in the evacuation.19
For Cambodians the date is a wound. Youk Chhang, director of the Documentation Center of Cambodia, calls 17 April 1975 one of the darkest days in the nation's history. Thirteen days after Phnom Penh, Saigon fell too.20 › The fall of Saigon, 1975
Visiting Phnom Penh today
Two places in and near the city keep the memory of what followed. The Tuol Sleng Genocide Museum in central Phnom Penh preserves the former S-21 prison, where the regime interrogated and tortured its prisoners, and the Choeung Ek Genocidal Center outside the city was its execution ground. In 2025 UNESCO inscribed both, with the former M-13 prison, on the World Heritage List as the Cambodian Memorial Sites. UNESCO describes them as former centers of repression that have become places of peace and reflection, and the museum asks its visitors to leave as messengers of peace.21
Notes
A number in the text points to a note; each note names the works that paragraph draws on, listed in full under Sources.
- Library of Congress, “The Fall of Phnom Penh”; ECCC, “Case 002/01: Summary of Appeal Judgement”; Genocide Studies Program, Yale, “Cambodian Genocide Program”; Genocide Watch, “April 17, 1975: The Khmer Rouge enter Phnom Penh”. ↩
- Library of Congress, “Democratic Kampuchea, 1975-78”; ECCC, “Case 002/01: Summary of Appeal Judgement”; Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”. ↩
- Library of Congress, “The Fall of Phnom Penh”; Dunham and Quinlan, The Bitter End; Samuel J. Cox, NHHC, “H-090-1: Operations Frequent Wind and Eagle Pull”. ↩
- Library of Congress, “Democratic Kampuchea, 1975-78”; Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”; Samuel J. Cox, NHHC, “H-090-1: Operations Frequent Wind and Eagle Pull”. ↩
- Library of Congress, “The Fall of Phnom Penh”; Samuel J. Cox, NHHC, “H-090-1: Operations Frequent Wind and Eagle Pull”; Dunham and Quinlan, The Bitter End. ↩
- Library of Congress, “Democratic Kampuchea, 1975-78”; Genocide Watch, “April 17, 1975: The Khmer Rouge enter Phnom Penh”; ECCC, “Case 002/01: Summary of Appeal Judgement”; Genocide Studies Program, Yale, “Cambodian Genocide Program”. ↩
- Library of Congress, “The Fall of Phnom Penh”; Samuel J. Cox, NHHC, “H-090-1: Operations Frequent Wind and Eagle Pull”; Dunham and Quinlan, The Bitter End. ↩
- Library of Congress, “The Fall of Phnom Penh”; Dunham and Quinlan, The Bitter End; Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”. ↩
- Library of Congress, “The Fall of Phnom Penh”; Samuel J. Cox, NHHC, “H-090-1: Operations Frequent Wind and Eagle Pull”; Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”. ↩
- Gerald R. Ford, “Indochina - Cambodia”; Dunham and Quinlan, The Bitter End; Samuel J. Cox, NHHC, “H-090-1: Operations Frequent Wind and Eagle Pull”. ↩
- Library of Congress, “The Fall of Phnom Penh”; Dunham and Quinlan, The Bitter End; Samuel J. Cox, NHHC, “H-090-1: Operations Frequent Wind and Eagle Pull”. ↩
- Library of Congress, “Democratic Kampuchea, 1975-78”; Genocide Watch, “April 17, 1975: The Khmer Rouge enter Phnom Penh”; Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”. ↩
- Library of Congress, “Democratic Kampuchea, 1975-78”; Genocide Watch, “April 17, 1975: The Khmer Rouge enter Phnom Penh”; Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”; Holocaust Memorial Day Trust, “Cambodia: 1975 to 1979”. ↩
- ECCC, “Case 002/01: Summary of Appeal Judgement”; Library of Congress, “Democratic Kampuchea, 1975-78”; Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”. ↩
- Library of Congress, “Democratic Kampuchea, 1975-78”; Genocide Watch, “April 17, 1975: The Khmer Rouge enter Phnom Penh”; Tyner and others, “The Evacuation of Phnom Penh during the Cambodian Genocide: Applying Spatial Video Geonarratives to the Study of Genocide”. ↩
- Library of Congress, “Democratic Kampuchea, 1975-78”; Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”. ↩
- Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”; Library of Congress, “Democratic Kampuchea, 1975-78”; Dunham and Quinlan, The Bitter End. ↩
- Library of Congress, “Democratic Kampuchea, 1975-78”; Holocaust Memorial Day Trust, “Cambodia: 1975 to 1979”; Genocide Studies Program, Yale, “Cambodian Genocide Program”; Genocide Watch, “April 17, 1975: The Khmer Rouge enter Phnom Penh”; USHMM, “Cambodia”. ↩
- ECCC, “Case 002/01: Summary of Appeal Judgement”; Genocide Studies Program, Yale, “Cambodian Genocide Program”. ↩
- Genocide Watch, “April 17, 1975: The Khmer Rouge enter Phnom Penh”; Samuel J. Cox, NHHC, “H-090-1: Operations Frequent Wind and Eagle Pull”; Dunham and Quinlan, The Bitter End. ↩
- UNESCO, “Cambodian Memorial Sites: From centres of repression to places of peace and reflection”; Tuol Sleng Genocide Museum, “Tuol Sleng Genocide Museum”. ↩
Sources
- Library of Congress, Federal Research Division, Cambodia: A Country Study (1987), “The Fall of Phnom Penh”
- Extraordinary Chambers in the Courts of Cambodia, Supreme Court Chamber, 23 November 2016, “Case 002/01: Summary of Appeal Judgement”
- Genocide Studies Program, Yale University, “Cambodian Genocide Program”
- Genocide Watch, with Youk Chhang, Documentation Center of Cambodia, “April 17, 1975: The Khmer Rouge enter Phnom Penh”
- Library of Congress, Federal Research Division, Cambodia: A Country Study (1987), “Democratic Kampuchea, 1975-78”
- Cambodgemag, “17 April 1975: How Phnom Penh fell to the Khmer Rouge”
- George R. Dunham and David A. Quinlan, U.S. Marines in Vietnam: The Bitter End, 1973-1975 (Washington: History and Museums Division, US Marine Corps, 1990), chapter 6, via Internet Archive
- Samuel J. Cox, Naval History and Heritage Command, H-Gram 090, “H-090-1: Operations Frequent Wind and Eagle Pull”
- Gerald R. Ford, letter to the Speaker of the House and the President of the Senate on the evacuation of Phnom Penh, 12 April 1975, Ron Nessen Papers, Box 12, “Indochina - Cambodia”, Gerald R. Ford Presidential Library
- Holocaust Memorial Day Trust, “Cambodia: 1975 to 1979”
- James A. Tyner and others, Genocide Studies and Prevention 12, no. 3 (2018), “The Evacuation of Phnom Penh during the Cambodian Genocide: Applying Spatial Video Geonarratives to the Study of Genocide”
- United States Holocaust Memorial Museum, “Cambodia”
- UNESCO World Heritage Centre, “Cambodian Memorial Sites: From centres of repression to places of peace and reflection”
- Tuol Sleng Genocide Museum, Ministry of Culture and Fine Arts of Cambodia, “Tuol Sleng Genocide Museum”
