Under the leadership of Pol Pot, General Secretary of the Communist Party of Kampuchea, the Khmer Rouge communist regime captured the capital Phnom Penh in 1975. The Khmer Rouge overthrew the pro-American Khmer Republic, and after the founding of the Royal Government of the National Union of Kampuchea, the Khmer Rouge held real power. From 1975 to 1979, the Khmer Rouge carried out mass killings in Cambodia in the name of 'ethnic cleansing'. It is estimated that there were 1.5 to 3 million unnatural deaths nationwide, accounting for about a quarter of the total population at that time.

The Khmer Rouge continued to receive strong support and assistance from the Chinese Communist Party (CCP), and Mao Zedong himself. According to statistics, China's aid accounted for at least 90% of the Khmer Rouge's total foreign aid. This included food, construction equipment, tanks, planes, artillery, and other materials.

The Khmer Rouge attempted to create an agricultural socialist society; they forced the entire urban population to move to the countryside. Following in the footsteps of China's Great Leap Forward resulted in massive deaths from disease, overwork, or malnutrition. A large-scale 'cleansing' of civilians and party personnel was carried out at the same time. In 1978 alone, 100,000 cadres and soldiers were killed in eastern Cambodia. After the overthrow of Democratic Kampuchea (the name of the state established by the Khmer Rouge), more than two million mass graves were discovered across the country. The Khmer Rouge death toll remains one of the highest in world history, especially given the short period of its rule.

References: [故事("StoryStudio)(Chinese)] (https://storystudio.tw/article/sobooks/first-they-killed-my-father-2/); [公視P#新聞實驗室 ("PTS P# Newslab")(Chinese)] (https://newslab.pts.org.tw/news/261-「秘密的滋味」 受害者回顧紅色高棉血淚史); [紐約時報中文網("New York Times Chinese Edition")(Chinese)] (https://cn.nytimes.com/china/20150331/c31history/); [二十一世紀雙月刊 ("Twenty-First Century Bimonthly")(Chinese)] (https://www.cuhk.edu.hk/ics/21c/media/articles/c037-199606004.pdf)