The Cambodian genocide was the systematic persecution and killing of Cambodian citizens by the Khmer Rouge under the leadership of Prime Minister of Democratic Kampuchea, Pol Pot. It resulted in the deaths of 1.5 to 2 million people from 1975 to 1979, nearly 25% of Cambodia's population in 1975.

The Cambodian–Vietnamese War was an armed conflict between Democratic Kampuchea, controlled by Pol Pot's Khmer Rouge, and the Socialist Republic of Vietnam. The war began with repeated attacks by the Liberation Army of Kampuchea on the southwestern border of Vietnam, particularly the Ba Chúc massacre which resulted in the deaths of over 3,000 Vietnamese civilians. On 23 December 1978, 10 out of 19 divisions of Khmer Rouge's military divisions opened fire along the shared Southwestern borderline with Vietnam with the goal of invading the Vietnamese provinces of Đồng Tháp, An Giang and Kiên Giang. On 25 December 1978, Vietnam launched a full-scale invasion of Kampuchea, and subsequently occupied the country in 2 weeks and removed the government of the Communist Party of Kampuchea from power. In doing so, Vietnam put an ultimate stop to the Cambodian Genocide, during which 25% of the Cambodian population had already been executed under Pol Pot’s regime.