Rooms of the Tuol Sleng Genocide Museum contain thousands of photos taken by the Khmer Rouge of their victims.
Analysis of 20,000 mass grave sites by the DC-Cam Mapping Program and Yale University indicate at least 1,386,734 victims of execution. Estimates of the total number of deaths resulting from Khmer Rouge policies, including 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. Cambodian journalist Dith Pran coined the term "killing fields" after his escape from the regime.
The Khmer Rouge regime arrested and eventually executed almost everyone suspected of connections with the former government or with foreign governments, as well as professionals and intellectuals. Ethnic Vietnamese, ethnic Thai, ethnic Chinese, ethnic Cham, Cambodian Christians, and the Buddhist monkhood were the demographic targets of persecution. As a result, Pol Pot has been described as "a genocidal tyrant." Martin Shaw described the Cambodian genocide as "the purest genocide of the Cold War era."
A commemorative stupa filled with the skulls of the victims at the Killing Field of Choeung Ek.
Ben Kiernan estimates that about 1.7 million people were killed. Researcher Craig Etcheson of the Documentation Center of Cambodia suggests that the death toll was between 2 and 2.5 million, with a "most likely" figure of 2.2 million. After 5 years of researching some 20,000 grave sites, he concludes that, "these mass graves contain the remains of 1,386,734 victims of execution." A UN investigation reported 2–3 million dead, while UNICEF estimated 3 million had been killed. Demographic analysis by Patrick Heuveline suggests that between 1.17 and 3.42 million Cambodians were killed, while Marek Sliwinski suggests that 1.8 million is a conservative figure. Even the Khmer Rouge acknowledged that 2 million had been killed—though they attributed those deaths to a subsequent Vietnamese invasion. By late 1979, UN and Red Cross officials were warning that another 2.25 million Cambodians faced death by starvation due to “the near destruction of Cambodian society under the regime of ousted Prime Minister Pol Pot,” who were saved by international aid after the Vietnamese invasion.
Cambodia's ethnic minorities constituted 15 percent of the population in pre-Khmer Rouge era. Of the 400,000 Vietnamese who lived in Cambodia before 1975, some 150–300,000 were expelled by the previous Lon Nol regime. When Pol Pot's Khmer Rouge came to power, there remained about 100–250,000 Vietnamese in the country. Almost all of them were repatriated by December 1975.
Mass grave at the Killing Field of Choeung Ek.
The Chinese community (about 425,000 people in 1975) was reduced to 200,000 during the next four years. In the Khmer Rouge's Standing Committee, four members were of Chinese ancestry, two Vietnamese, and two Khmers. Some observers argue that this mixed composition makes it difficult to argue that there was an intent to kill off minorities. R.J. Rummel, an analyst of political killings, argues that there was a clear genocidal intent:
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 center of Cambodian culture, its spiritual incarnation, its institutions....As part of a planned genocide campaign, the Khmer Rouge sought out 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.
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