The Cambodian genocide was the systematic persecution and killing of Cambodians by the Khmer Rouge under the leadership of Pol Pot, who radically pushed Cambodia towards communism. It resulted in the deaths of 1.5 to 2 million people from 1975 to 1979, nearly a quarter of Cambodia's 1975 population.

Pol Pot, born Saloth Sar led the Khmer Rouge from 1963 until 1997. Sar left attended the École Miche, a Catholic school in Phnom Penh. Later in Paris, Sar was exposed to anti-colonial, revolutionary, and socialist ideas. He became increasingly radical, outraged by French colonialism. Thus Sar became a founding member of the Khmer Rouge, a party dedicated to socialist revolution in Cambodia. The Khmer Rouge’s ideology combined elements of Marxism with an extreme version of Khmer nationalism and xenophobia.

Pol Pot was born Saloth Sar
Pol Pot declared 1975 "Year Zero," literally the beginning of the end of the modern world. The ideological aim of their revolution was to recreate a “pure” rural society - “Classless and glorious” similar to that of the Khmer Empire of the tenth century. Because there were so few Khmer Rouge, who probably represented no more than 10 per cent of the population – the Angkar sort to control the population by enslaving it and reducing it by half.

Pol Pot and Khmer Rouge had long been supported by the Communist Party of China (CPC) and Mao Zedong; it is estimated that at least 90% of the foreign aid to Khmer Rouge came from China, with 1975 alone seeing at least US$1 billion in interest-free economic and military aid from China. After seizing power in April 1975, the Khmer Rouge wanted to turn the country into a socialist agrarian republic, founded on the policies of ultra-Maoism and influenced by the Cultural Revolution.

Mao mets Pol Pot
Pol Pot and Khmer Rouge officials with Mao Zedong, Beijing, June 1975

Pol Pot and other Khmer Rouge officials met with Mao in Beijing in June 1975, receiving approval and advice, while high-ranking CPC officials such as Zhang Chunqiao later visited Cambodia to offer help. To fulfil its goals, the Khmer Rouge emptied the cities and forced Cambodians to relocate to labour camps in the countryside, where mass executions, forced labour, physical abuse, malnutrition, and disease were rampant. They also started the “Maha Lout Ploh”, copying the “Great Leap Forward” of China that caused tens of millions of deaths in the Great Chinese Famine. In 1976, the Khmer Rouge changed the name of the country to Democratic Kampuchea.

Mao Zedong with Cambodian Prime Minister Binu Prince, August 27, 1975
Mao Zedong with Cambodian Prime Minister Binu Prince, August 27, 1975

By January 1979, 1.5 to 2 million people had died due to the Khmer Rouge's policies, including 200,000-300,000 Chinese Cambodians, 90,000 Muslims, and 20,000 Vietnamese Cambodians. 20,000 people passed through the Security Prison 21, one of the 196 prisons the Khmer Rouge operated, and only seven adults survived. The prisoners were taken to the Killing Fields, where they were executed (often with pickaxes, to save bullets) and buried in mass graves.

Abduction and indoctrination of children was widespread, and many were persuaded or forced to commit atrocities. As of 2009, the Documentation Center of Cambodia has mapped 23,745 mass graves containing approximately 1.3 million suspected victims of execution. Direct execution is believed to account for up to 60% of the genocide's death toll, with other victims succumbing to starvation, exhaustion, or disease.

“Various studies have estimated the death toll at between 740,000 and 3,000,000, most commonly between 1.4 million and 2.2 million, with perhaps half of those deaths being due to executions, and the rest from starvation and disease. An additional 300,000 Cambodians starved to death between 1979 and 1980, largely as a result of the after-effects of Khmer Rouge policy.”.

The genocide triggered the second outflow of refugees, many of whom escaped to neighbouring Vietnam and, to a lesser extent, Thailand. The Vietnamese invasion of Cambodia ended the genocide by defeating the Khmer Rouge in January 1979. On 2 January 2001, the Cambodian government established the Khmer Rouge Tribunal to try the members of the Khmer Rouge leadership responsible for the Cambodian genocide. Trials began on 17 February 2009. On 7 August 2014, Nuon Chea and Khieu Samphan were convicted and received life sentences for crimes against humanity during the genocide.

“Anyone thought to be an intellectual of any sort was killed. Often people were condemned for wearing glasses or knowing a foreign language. Ethnic Vietnamese and Cham Muslims in Cambodia were also targeted. Hundreds of thousands of the educated middle-classes were tortured and executed in special centres.”.

In 1968, the Khmer Rouge officially launched a national insurgency across Cambodia. Though North Vietnam had not been informed of this decision, its forces provided shelter and weapons to the Khmer Rouge after the insurgency started. North Vietnamese support for the Khmer Rouge's insurgency made it impossible for the Cambodian military to effectively counter it. For the next two years, the insurgency grew because Norodom Sihanouk did very little to stop it. As the insurgency grew stronger, the party finally openly declared itself to be the Communist Party of Kampuchea.

Mao Zedong, Peng Zhen, Norodom Sihanouk and Liu Shaoqi
Mao Zedong, Peng Zhen, Norodom Sihanouk and Liu Shaoqi (1965)

Sihanouk was removed as head of state in 1970. Premier Lon Nol deposed him with the support of the National Assembly, establishing the pro-United States Khmer Republic. On the Communist Party of China (CPC)'s advice, Sihanouk, in exile in Beijing, made an alliance with the Khmer Rouge and became the nominal head of a Khmer Rouge–dominated government-in-exile (known by its French acronym, GRUNK) backed by China. Although thoroughly aware of the weakness of Lon Nol's forces and loath to commit American military force to the new conflict in any form other than airpower, the Nixon administration announced its support for the new Khmer Republic.

On 29 March 1970, North Vietnam launched an offensive against the Cambodian army. Documents uncovered from the Soviet Union's archives reveal that the invasion was launched at the Khmer Rouge's explicit request after negotiations were held with Nuon Chea. A North Vietnamese force quickly overran large parts of eastern Cambodia, reaching within 15 miles (24 km) of Phnom Penh before being pushed back. By June, three months after Sihanouk's removal, they had swept government forces from the entire northeastern third of the country. After defeating those forces, the North Vietnamese turned the newly won territories over to the local insurgents.

Skulls lie in the killing fields of Choeung Ek
Skulls lie in the killing fields of Choeung Ek.

The Khmer Rouge also established “liberated” areas in the south and the southwestern parts of the country, where they operated independently of the North Vietnamese. After Sihanouk showed his support for the Khmer Rouge by visiting them in the field, their ranks swelled from 6,000 to 50,000 fighters. Many of the recruits were apolitical peasants who fought supporting the king, not for communism, of which they had little understanding. By 1975, with Lon Nol's government running out of ammunition and having lost U.S. support, it was clear that it was only a matter of time before it would collapse. On 17 April 1975, the Khmer Rouge captured Phnom Penh and ended the civil war.

Since the 1950s, Pol Pot had made frequent visits to the People's Republic of China, receiving political and military training—especially on the theory of Dictatorship of the proletariat—from the personnel of the CPC. From November 1965 to February 1966, high-ranking CPC officials such as Chen Boda and Zhang Chunqiao trained him on topics such as the communist revolution in China, class conflicts, Communist International, etc. Pol Pot also met with other officials, including Deng Xiaoping and Peng Zhen. He was particularly impressed by Kang Sheng's lecture on political purge.

A Khmer Rouge soldier waves his pistol and orders store owners to abandon their shops in Phnom Penh, Cambodia, as communist forces take over the capital in April, 1975.
A Khmer Rouge soldier waves his pistol and orders store owners to abandon their shops in Phnom Penh, Cambodia, as communist forces take over the capital in April, 1975.

In 1970, Lon Nol overthrew Sihanouk, and the latter fled to Beijing, where Pol Pot was also visiting. On the advice of CPC, Khmer Rouge changed its position to support Sihanouk, establishing the National United Front of Kampuchea. In 1970 alone, the Chinese reportedly gave the United Front 400 tons of military aid. In April 1974, Sihanouk and Khmer Rouge leaders Ieng Sary and Khieu Samphan met with Mao in Beijing; Mao agreed on the policies Khmer Rouge proposed but was against marginalizing Sihanouk in a new Cambodia after winning the civil war. In 1975, Khmer Rouge defeated the Khmer Republic and started the Cambodian genocide.

Young Cambodian boy beside hundreds of skulls

In June 1975, Pol Pot and other Khmer Rouge officials met with Mao in Beijing, where Mao taught Pot his “Theory of Continuing Revolution under the Dictatorship of the Proletariat”, recommended two relevant articles by Yao Wenyuan, and sent him over 30 books authored by Karl Marx, Friedrich Engels, Vladimir Lenin and Joseph Stalin.

During the meeting, Mao said to Pol Pot:

“We agree with you! Much of your experience is better than ours. China is not qualified to criticize you. We committed errors of the political routes for ten times in fifty years—some are national, some are local…Thus, I say China has no qualification to criticize you but have to applaud you. You are basically correct…During the transition from the democratic revolution to adopting a socialist path, there exist two possibilities: one is socialism, the other is capitalism. Our situation now is like this. Fifty years from now, or one hundred years from now, the struggle between two lines will exist. Even ten thousand years from now, the struggle between two lines will still exist. When Communism is realized, the struggle between two lines will still be there. Otherwise, you are not a Marxist...... Our state now is, as Lenin said, a capitalist state without capitalists. This state protects capitalist rights, and the wages are not equal. Under the slogan of equality, a system of inequality has been introduced. There will exist a struggle between two lines, the struggle between the advanced and the backward, even when Communism is realized. Today, we cannot explain it completely”.

Pol Pot replied:

“The issue of lines of struggle raised by Chairman Mao is an important strategic issue. We will follow your words in the future. I have read and learned various works of Chairman Mao since I was young, especially the theory on people's war. Your works have guided our entire party”.

On the other hand, during another meeting in August 1975, Chinese Premier Zhou Enlai warned Sihanouk as well as Khmer Rouge leaders including Khieu Samphan and Ieng Sary of the danger of radical movement towards communism, citing the mistakes in China's own Great Leap Forward. Zhou urged them not to repeat the mistakes that caused havoc. Sihanouk later recalled that Khieu Samphan and Ieng Thirith responded only with "an incredulous and superior smile”.


During the genocide, China was the Khmer Rouge's main international patron, supplying “more than 15,000 military advisers” and most of its external aid. It is estimated that at least 90% of foreign aid to Khmer Rouge came from China, with 1975 alone seeing US$1 billion in interest-free economics and military aid, “the biggest aid ever given to anyone country by China”. But a series of internal crises in 1976 prevented Beijing from exerting substantial influence over Khmer Rouge policies.

Ideology played an important role in the genocide. Pol Pot was influenced by Marxism and wanted an entirely self-sufficient agrarian society free of foreign influence. Stalin's work has been described as a “crucial formative influence” on his thought. Also, heavily influential was Mao's work, particularly On New Democracy. In the mid-1960s, Pol Pot reformulated his ideas about Marxism-Leninism to suit the Cambodian situation, aiming to bring Cambodia back to its “mythic past” of the powerful Khmer Empire, to stop corrupting influences like foreign aid and western culture, and to restore an agrarian society.

A child soldier with a human skull resting on the tip of his rifle. Dei Kraham, Cambodia. 1973.
A child soldier stands over a blindfolded soldier — Angkor Chey, Cambodia. 1973.

Pol Pot's strong belief in an agrarian utopia stemmed from his experience in Cambodia's rural northeast, where, while the Khmer Rouge gained power, he developed an affinity for the agrarian self-sufficiency of the area's isolated tribes. Attempts to implement these goals (formed from small rural communes) into a larger society were key factors in the ensuing genocide. One Khmer Rouge leader said the killings were meant for the “purification of the populace.”

“One estimate is that out of 40,000 to 60,000 monks, only between 800 and 1,000 survived to carry on their religion. We do know that of 2,680 monks in eight monasteries, a mere seventy were alive as of 1979. As for the Buddhist temples that populated the landscape of Cambodia, the Khmer Rouge destroyed 95 percent of them, and turned the remaining few into warehouses or allocated them for some other degrading use. Amazingly, in the very short span of a year or so, the small gang of Khmer Rouge wiped out the centre of Cambodian culture, its spiritual incarnation, its institutions….As part of a planned genocide campaign, the Khmer Rouge sought and killed other minorities, such as the Moslem Cham. In the district of Kompong Xiem, for example, they demolished five Cham hamlets and reportedly massacred 20,000 that lived there; in the district of Koong Neas only four Cham apparently survived out of some 20,000”.

The Khmer Rouge forced virtually Cambodia's entire population into mobile work teams. Michael Hunt has written that it was “an experiment in social mobilization unmatched in twentieth-century revolutions.” The Khmer Rouge used an inhumane forced labour regime, starvation, forced resettlement, land collectivization, and state terror to keep the population in line. Ben Kiernan has compared the Cambodian genocide to the Armenian Genocide perpetrated by the Ottoman Empire during The First World War.

“the purest genocide of the Cold War era”.

The Khmer Rouge regime frequently arrested and often executed anyone suspected of connections with the former Cambodian government or foreign governments, as well as professionals, intellectuals, the Buddhist monkhood, and ethnic minorities. Even those who were stereotypically thought of as having intellectual qualities, such as wearing glasses or speaking multiple languages, were executed for fear that they would rebel against the Khmer Rouge. As a result, Pol Pot has been described by journalists and historians such as William Branigin as “a genocidal tyrant”.

British sociologist Martin Shaw described the Cambodian genocide as “the purest genocide of the Cold War-era”. The attempt to purify Cambodian society along racial, social and political lines led to purges of Cambodia's previous military and political leadership, along with business leaders, journalists, students, doctors, and lawyers.

Ethnic Vietnamese, ethnic Thai, ethnic Chinese, ethnic Cham, Cambodian Christians, and other minorities were also targeted. The Khmer Rouge forcibly relocated minority groups and banned their languages. By decree, the Khmer Rouge banned the existence of more than 20 minority groups, which constituted 15% of the country's population.

A line of a thousand Cambodian refugees makes it into Thailand - Klong Kwang, Thailand. 1979.
Starving refugees get help from a Thai relief mission, laying in tents near the border. Pailin, Cambodia. 1979.
Young refugees hide under tall grass, escaping from the killing fields of the Khmer Rouge.

Killing Fields

The Killing Fields are several sites in Cambodia where collectively more than a million people were killed and buried by the Khmer Rouge regime (the Communist Party of Kampuchea) during its rule of the country from 1975 to 1979, immediately after the end of the Cambodian Civil War (1970–1975). The mass killings are widely regarded as part of a broad state-sponsored genocide (the Cambodian genocide).

A field of people massacred by the Khmer Rouge. — My Duc, Vietnam. 1978.

Analysis of 20,000 mass grave sites by the DC-Cam Mapping Program and Yale University indicates at least 1,386,734 victims of execution. Estimates of the total deaths resulting from Khmer Rouge policies, including death from disease and starvation, range from 1.7 to 2.5 million out of a 1975 population of roughly 8 million. In 1979, Vietnam invaded Democratic Kampuchea and toppled the Khmer Rouge regime; viewed as ending the genocide.

Security Prison 21, Tuol Sleng

From 1975 to 1979, an estimated 20,000 people accused of crimes against the state or of espionage were taken to Tuol Sleng. Offenses that could lead to such a fate could be as minor as breaking a factory machine or mishandling farming tools. Often times, the entire family of a prisoner were captured and taken to Tuol Sleng, where their fate was shared with their accused relative.

Upon arrival, prisoners were asked to provide a detailed biography of their life up to their detainment, and were then photographed before being placed in the prison.Tuol Sleng held up to 1,500 prisoners at a time. All lived in unhygienic and inhumane conditions. Prisoners were forbidden to speak to one another and spent their days shackled to either the wall or each other.

Prisoners were given two bowls of rice porridge and one bowl of leaf soup a day. Once every four days, prisoners were hosed down en masse by prison staff.

A young girl and her baby, inside of Tuol Sleng. Phnom Penh.
A terrified prisoner is photographed inside the Tuol Sleng prison. Of the nearly 20,000 people locked in Tuol Sleng, only seven survived. Phnom Penh.
A prisoner bleeds on the floor of Tuol Sleng. Phnom Penh.

Interrogations began within a few days of incarceration in the “cold” unit, which could not use torture and instead relied on verbal coercion and “political pressure” to elicit confessions. If the confession taken by the cold unit was not sufficient, prisoners were then taken to the “hot unit,” which employed torture to get confessions.

Their methods included

“beating with fists, feet, sticks or electric wire; burning with cigarettes; electric shocks; being forced to eat faeces; jabbing with needles; ripping out fingernails; suffocation with plastic bags; water boarding; and being covered with centipedes and scorpions.”.

The confession process could last for weeks or months, and since full confessions were required, the medical unit was primarily tasked with keeping prisoners alive during interrogations. The product of these interrogations revealed more about the paranoid state of the Khmer Rouge than the prisoners: Confessions became intricate stories of coordinated attacks against the state with hundreds.

Confessions concluded with lists of co-conspirators that sometimes ran over a hundred people long. These supposed co-conspirators would then be interrogated and sometimes themselves brought to Security Prison 21. After confessions concluded, prisoners were handcuffed and forced to dig shallow pits that would be used as their own mass graves. Due to international sanctions and a collapsed economy, bullets became scarce in Cambodia. Instead of guns, executioners were forced to use makeshift weapons like pickaxes and iron bars to carry out mass executions. Oftentimes, their screams were covered with loudspeakers playing propaganda music of Democratic Kampuchea and noise from generator sets.

“Tortures were so atrocious and heinous that the prisoners tried in every way to commit suicide, even using spoons, and their hands were constantly tied behind their back to prevent them from committing suicide or trying to escape”.

Initially, prisoners were executed and buried near the premises of Security Prison 21, but by 1976, all available burial space around the prison had been used. After 1976, all prisoners were sent to the Choeung Ek execution centre, one of 150 used by the Khmer Rouge during the Cambodian genocide. While the prisoners in the first years of the prison's operations were primarily members of the previous government, Khmer Rouge members suspected of being a threat to leadership were increasingly detained at Security Prison 21 during its later years. There, they would be interrogated by the “chew unit,” a unit formed solely for interrogating special cases.

Inside S-21, a special treatment was given to babies and children; they were taken away from their mothers and relatives, and sent to the Killing Fields, where they were smashed against the so-called Chankiri Tree. It was so the children “wouldn't grow up and take revenge for their parents' deaths”. Some of the soldiers laughed as they beat the children against the trees, as not laughing could have indicated sympathy, making oneself a target. A similar treatment is supposed to have been given to babies of other prisons like S-21, spread all over Democratic Kampuchea.

"Happy is the one who seizes your infants and dashes them against the rocks" - Psalm 137:9

Similarly, prison staff had to obey nearly impossible regulations with fatal consequences if they failed to comply. From prison records, 563 guards and other staff of Tuol Sleng were executed. Non-Cambodians were also taken to Tuol Sleng, with 11 Westerners' cases being processed and then executed in the prison.

In the above photo is Christopher Edward DeLance, an American who mistakenly went into Cambodian waters in 1978. DeLance was forced to sign a confession that he was a CIA spy, and was subsequently executed a week before the Vietnamese invasion.

Alleged photographs and forced confessions of nine missing Western yachtsmen (four Americans, two Australians, plus those of John Dewhirst and Kerry Hamill) were found in the prison files. The confessions of Dewhirst and Hamill revealed that they had been seized by a Khmer Rouge patrol vessel near the island of Koh Tang on the evening of 13 August 1978. Stuart Glass, the Canadian befriended by Dewhirst and Hamill, had been shot and killed during Foxy Lady's capture. Hamill and Dewhirst were both brought ashore and then taken by truck to Phnom Penh.

Like the other Western yachtsmen, they were almost certainly tortured. The extent of their mistreatment is not clear. Dewhirst wrote several long confessions that mixed true events in his life with false accounts of his career as a CIA agent planning to subvert the Khmer Rouge regime. He claimed that his father (also an agent) had been paid a large bribe for inducting his son into the CIA, and that his college course in Loughborough was interspersed with training as a spy. Dewhirst and Hamill signed a series of confessions between 3 September and 13 October 1978.

During the 2009 trial of S-21 chief Kang Kek Iew, a former S-21 guard named Cheam Sour claimed that one of the eight Western yachtsmen held at S-21 was burned to death. Kang Kek Iew said that he received orders from his superiors that the bodies of the murdered westerners had to be burned to remove all traces of their remains, adding, “I believe that nobody would dare to violate my orders”.

Ethnic Chinese, Vietnamese, and Thai were targets of the Khmer Rouge, which sought to remake the country into a strictly Cambodian agricultural society. Of 450,000 Chinese in Cambodia in 1975, only 200,000 remained by 1979.