The ‘Know Your Region’ series is designed to support unit and individual professional military education on the South East Asian region. It’s important for all serving members of our military to have a foundational knowledge of the countries and issues in the Indo-Pacific.


On this page:

  • The Khmer Rouge Regime
  • Australia and Cambodia

Content Warning: descriptions and images of mass violence, sexual assault, and torture.


The Khmer Rouge Regime

In 1970 a coup deposed the Cambodian King and the new Cambodian Government, the Khmer Republic, and ordered Vietnamese forces out of the country. The Vietnamese responded by advancing on the Cambodian capital, Phnom Penh. South Vietnamese and American forces also invaded in an unsuccessful attempt to drive out Vietnamese communists. Cambodia meanwhile began to descend into a civil war, with the Government fighting Cambodian communists, commonly known as the Khmer Rouge. The ousted King also raised a force and formed an alliance with the Khmer Rouge, fighting against the Government. China supported the Cambodian communists, while the United States supported the Cambodian government. In 1973 the U.S. carried out massive bombing raids against Khmer Rouge targets. In 1975 the Khmer Rouge captured Phnom Penh. It is estimated that half a million Cambodians died during the civil war and thousands became refugees. Though even worse was to come.

The Khmer Rouge – which translates as Red Cambodians but is also known among Cambodians as ‘Pol Pot time’ – marks a dark period for the country. The main goal of the Communist Party of Kampuchea (CPK), led by Pol Pot, was to create a socialist society where modern influences of the urban population ('New People') were to be eradicated in order to return Cambodia to a pre-modern society of 'Old People'. After overthrowing the pro-American Khmer Republic, the CPK renamed the country Democratic Kampuchea and ruled from 1975 to 1979.

Many deaths resulted from the regime's social engineering policies and the 'Moha Lout Plaoh' which was an imitation of China's flawed Great Leap Forward. The Khmer Rouge's attempts at agricultural reform through collectivisation similarly led to widespread famine, while its insistence on absolute self-sufficiency even in the supply of medicine led to the death of many thousands from treatable diseases such as malaria. Consequently, millions of Cambodians were killed (an estimated 1.5 to 3 million) due to execution, forced hardships, disease, and starvation. Buddhist monks, urban dwellers, government officials and people with a Western education were perceived by the regime as supporters of the 'New People' culture and, as such, were among the initial targets of the regime. Although the Khmer Rouge started with the murder of perceived political opponents, the violence quickly spiralled to include the attempted genocide of Cambodian minorities to engender national purity, and eventually engulfed the remaining population. Ultimately, the mass crimes against humanity led to the death of nearly 25% of the population at the time. To learn about the Fall of Phnom Penh, watch the report below.

Most Cambodians were forced to evacuate urban areas into labour camps in rural Cambodia in order to work in farming. The evacuees were sent on long marches to their assigned villages, then required to write autobiographical essays. This content was used to determine their fate by the Khmer Rouge forces. Military officers and educated professionals were usually sent for re-education, which in practice meant immediate execution or confinement in a labour camp. Those with specialist technical skills were sent back to cities to restart production in factories which had been interrupted by the takeover. The remaining displaced urban population were placed in agricultural communes to increase food production. People were not allowed to go outside their cooperative. The regime would not allow anyone to gather and hold discussions. If three people spoke together, they could be accused of being enemies and arrested or executed.

Under the terms of the CPK’s 1976 'Four-Year Plan,' Cambodians were expected to produce three tons of rice per hectare throughout the country, despite normally producing only one ton. This meant that people had to try to grow and harvest rice the whole year. In most regions, the Khmer Rouge forced people to work more than 12 hours a day without rest or adequate food.

The Santebal were the secret police of Democratic Kampuchea and in charge of internal security and running prison camps. Tuol Sleng, which was Santebal's headquarter and a former high school, could hold up to 1,500 prisoners at a time and was the primary location of torture, summary executions, and purges. Between 1976 and 1978, around 20,000 Cambodians were held at Tuol Sleng (S-21). Of this number only seven adults and five children are known to have survived. However, Tuol Sleng was one of at least 150 execution centres in the country.

Purges were frequent under the regime. As an example, at the end of 1976, following disappointing rice harvests in the northwestern zone, the party centre ordered a purge. Troops from the western and southwestern zone were ordered into the northwestern zone. Over the next year, senior cadre and numerous lower ranking leaders were killed. The chaos caused by this purge allowed many peasants to escape the northwestern zone and seek refuge in Thailand. For more information on Cambodia under the Khmer Rouge – dubbed the ‘prison without walls’ – watch the following video.

In the 1970s, the Khmer Rouge were largely supported and funded by the Chinese Communist Party. Fearing a Vietnamese attack, Pol Pot ordered a pre-emptive invasion of their neighbour on 18 April 1978. The regime forces crossed the border and looted nearby villages, mostly in the border town of Ba Chúc. Of the 3,157 civilians who lived there, only two survived the massacre. These Cambodian forces were repelled by the Vietnamese military forces. After several years of border conflict and the flood of refugees fleeing Kampuchea, relations collapsed by December 1978.

The regime was removed from power in 1979 when Vietnam invaded from the east and quickly destroyed most of the Khmer Rouge's forces and captured the capital on 7 January 1979. The remaining elements fled to Thailand but continued to control certain mountainous areas – such as Phnom Malai and Anlong Veng – to exert influence while in exile. These Khmer Rouge bases were funded by diamond and timber smuggling, military assistance from China, and goods smuggled from markets. Critically, the Khmer Rouge were able to hold onto Cambodia's United Nations seat (with considerable international support) until 1993. In September, the monarchy was restored and the country's name changed to the Kingdom of Cambodia.

Although the Vietnamese captured Phnom Penh at the start of 1979, fighting continued for another ten years and the situation deteriorated into civil war. The Cambodian Government – then a puppet of the Vietnamese government – fought a coalition of forces, of which the Khmer Rouge was the strongest. In 1989 Vietnamese troops withdrew from Cambodia but the peace was fragile as the warring parties could not agree on a power-sharing arrangement that would bring lasting peace to the country and enable free elections. A year later, thousands of Khmer Rouge guerrillas surrendered themselves in an official amnesty.

The end of the Cold War brought the possibility of peace for Cambodia and diplomatic negotiation efforts were ramped up. The different factions and the international community agreed on an arrangement in which Cambodian sovereignty was vested in a Supreme National Council, made up of members from the different factions. Cambodia's administration and the first general election would be overseen by the United Nations (UN), which would also be responsible for the country's security. The deal was signed in Paris in October 1991 and became known as the Paris Agreement. To facilitate the agreement, the UN passed a resolution establishing the United Nations Advance Mission in Cambodia (UNAMIC). The Mission was to help create a neutral environment in which Cambodia's warring factions could disarm and de-mobilise. It was a precursor to the larger United Nations Transitional Authority in Cambodia (UNTAC), deployed in 1992.

In the Paris Peace Agreement of 1991, all parties to the conflict agreed to this solution. The result was a large and complex United Nations operation employing 1,000 civilians, 3,600 civilian police, and 16,000 military personnel. Very soon however, the Khmer Rouge withdrew its cooperation. Rather than attempt a peace enforcement operation for which it had neither the strength nor the political backing, the United Nations force pressed on with the planned elections in May 1993. The elections were an outstanding success. Despite intimidation by the Khmer Rouge, about 90% of eligible Cambodians registered and voted and a fragile democracy was given a chance of life. Yet, it was not until the end of 1999 when the Khmer Rouge effectively ceased to exist. Check out the video below to learn more about this chaotic period.

Cambodia has gradually recovered from the Khmer Rouge, although the psychological scars affect the entire population. Nearly all families were affected by the Khmer Rouge regime, experiencing immense loss or separation, suffering and trauma. While over half of the population has been born since the regime ended (half of the population are between the ages of 0 and 24), the after-effects of the regime are still felt today. Several hundred thousand Cambodians fled their country and became refugees. Millions of mines were laid by the Khmer Rouge and government forces, which have led to thousands of deaths and disabilities since the 1980s.

The Extraordinary Chambers in the Courts of Cambodia (ECCC) was established as a Cambodian court with international participation and assistance to bring to trial senior leaders and those most responsible for crimes committed during the regime. In 2014, two Khmer Rouge leaders, Nuon Chea and Khieu Samphan, were jailed for life by a United Nations backed court which found them guilty of crimes against humanity for their roles in the Khmer Rouge's genocidal campaign. There are still open cases. It is important to differentiate between the attempted genocide of ethnic and religious minorities, such as the ethnic Vietnamese and Cham, and the crimes against humanity of the Khmer ethnic group.

The buildings of Tuol Sleng have been preserved and turned into the Tuol Sleng Museum of Genocide. The Khmer Rouge photographed the vast majority of the inmates and left a photographic archive behind. These black-and-white photographs now line the rooms and enable visitors to see almost 6,000 S-21 portraits on the walls. Visitors can also learn how the inmates were tortured from the equipment and facilities exhibited in the buildings.

The Choeung Ek Killing Fields are located about 15 kilometres outside of Phnom Penh. Most of the prisoners who were held captive at S-21 were taken to the fields to be executed and deposited in one of the 129 mass graves, 43 have been left untouched. It is estimated that the graves contain the remains of over 20,000 victims. After its discovery in 1979, the Vietnamese transformed the site into a memorial and stored skulls and bones in an open-walled wooden memorial pavilion. Eventually, these remains were showcased in the memorial's centrepiece stupa, or Buddhist shrine, to educate Cambodians – and the world – about what happened, while also commemorating those who died. A memorial ceremony is held on 9 May each year, at which Khmer Rouge survivors and their relatives, officials, students, and other Cambodians gather at the stupa to remember the dead.


Australia and Cambodia

In Cambodia, the United Nations attempted an ambitious operation and for a time took over responsibility for the state. Australia had played a major role in helping to arrive at a political settlement and provided the force commander for the operation which followed. In the power vacuum and civil war that followed Vietnamese withdrawal in 1989, Australia promoted the idea of a United Nations transitional administration to take over Cambodia until elections could be held. Canberra and Phnom Penh established diplomatic relations in 1952. Our strong support for the Cambodian Peace Process in the late 1980s and early 1990s, including our leading role in the UNTAC (1992-1993), is still appreciated by the Cambodian people.

Australia provided the signallers for UNAMIC by committing 65 personnel in October 1991. UNAMIC consisted of military observers, a signals unit, and support personnel. It initially helped maintain the ceasefire and later tasks included running a mine detection and clearance training program for Cambodians. In March 1992 UNAMIC was absorbed by UNTAC.

UNTAC was established to supervise the ceasefire and subsequent general election. It was a large force consisting of 12 infantry battalions and support units, military observers, and civilian police, totalling 22,000 personnel from 32 different countries. The military component was commanded by an Australian officer, Lieutenant General John Sanderson. A further 14 Australians served on UNTAC's headquarters staff. Australia provided the first contingent – the Force Communications Unit (488 personnel) – which was mainly from the 2nd Signals Regiment. The second contingent included RAN, RAAF, and New Zealand Army personnel. The signallers were attached to units throughout Cambodia to maintain contact with the force's headquarters. Sanderson would later comment they "were the glue that held the mission together".

Australia's contribution increased as the election came closer. Between May and September 1992 Australia sent a movement-control group, with members from the three services. Between May and July 1993, the period covering the general election, Canberra sent an additional 115 Australian troops and six Blackhawk helicopters from the 5th Aviation Regiment and 2/4 RAR. The deployment was tense. By July 1992 the Khmer Rouge had effectively withdrawn from the peace agreement and was feared to disrupt UNTAC's operations. There were a number of small skirmishes and mortar attacks. An Australian signaller was taken hostage when he and three Thai military observers were captured by the Khmer Rouge and detained for several hours.

The Australian Federal Police sent a detachment to UNTAC to serve with the civilian police component. Personnel from the Australian Electoral Commission were also sent to Cambodia, as part of UNAMIC, to help prepare for the general election. Much of their work related to voter education and registration. Cambodia had not had a free election since the early 1950s and did not have a democratic tradition. Considered a successful 1993 election, UNTAC began withdrawing from Cambodia, which was completed by November. Watch the Australian War Memorials video below to learn more about Australia’s involvement in the Kingdom.

Australia's approach to modern bilateral relationship with Cambodia enables the two countries to engage on issues of bilateral, regional and strategic importance, and supports improvements that benefit Cambodian people. Canberra and Phnom Penh work together on a range of common strategic interests in regional and global fora. Both are co-members of the East Asia Summit, the ASEAN Regional Forum, and Asia-Europe Meeting. Australia's ongoing development partnership with Cambodia has three pillars: health security, stability, and economic recovery. Over a dozen initiatives have already been completed.

The Australian Embassy in Phnom Penh closely monitors political developments and the human rights situation in Cambodia and raises issues of concern directly with the Cambodian Government. Multilaterally, Australia has made statements about Cambodia in the UN Human Rights Council and during Cambodia's third Universal Periodic Review in January 2019.

People to people links between Australia and Cambodia are an important aspect of our relationship. Connections are forged through education, tourism, and culture. There are over 66,000 people of Cambodian origin living in Australia according to the 2016 Census (just over 33,000 born in Cambodia and another 45,700 citizens with Cambodian ancestry). Cambodian refugees began arriving in Australia after the Khmer Rouge regime gained power in 1975, with numbers peaking in the 1980s. Approximately 6,000-7,000 Australians reside in Cambodia, most being dual Cambodian-Australian citizens or expatriates involved in development assistance work or business. The following ABC News report updates Australia’s long-relations with Cambodia.


The first recorded Cambodia-born migrants to Australia were a family of nine who arrived in the late 1940s. Following Cambodia's independence from French rule in 1953, Cambodian students began coming to Australia in small numbers. During the 1960s and early 1970s, larger groups of students came to Australia under the Colombo Plan, many of whom actually settled in Australia. The Cambodia-born population in Australia remained relatively small up until the Khmer Rouge period between 1975 to 1979. Many fled Cambodia and spent years in refugee camps located in various neighbouring countries such as Thailand, waiting for the possibility of relocating. Australia was one of the main receiving countries of Cambodian refugees in the post-Khmer Rouge regime period. By June 1976, the Cambodia-born population in Australia increased to 500 people. Between April 1975 and June 1986, 12,813 Cambodians came to Australia under the Refugee and Special Humanitarian Program.

Due to the events of the Khmer Rouge and subsequent events, most Cambodians who migrated to Australia between 1975 and 1986 have suffered from physical and psychological trauma, including forced separation from their families. Moreover, some community leaders in Australia believe that the Cambodian population figures in Australia are understated due to some Cambodians being born in refugee camps in Vietnam and Thailand, while others were born in their first settlement country.

The following wave of migration was generally through sponsored relatives of the earlier waves, with many Cambodian-born people arriving in Australia under the family migration stream. The majority of the Cambodia-born population in Australia identify as Buddhist (79.5%). Throughout Australia, there are various Cambodian social and cultural associations that provide the Cambodian community strong support networks. This is seen in the following video.

Explore the following resources to learn more about the Cambodian-Australian community:


Discussion Questions:

  1. Australian contribution to the UNTAC mission set the foundation for modern intervention in regional issues. Follow-on efforts included East Timor and the Solomon Islands. What were the key lessons learnt from UNTAC? How would the ADF go about such a mission today? How can the ADF support the Cambodian military modernise and support regional stability activities?
  2. China is looking to increase its influence in Cambodia and has engaged the nation under the Belt and Road initiative. What might this mean to trilateral military activities with Cambodia? What would this mean to ASEAN and FPDA activities?