Vietnamese occupation and the PRK (1979–93)

Main articles: People's Republic of Kampuchea and Cambodian–Vietnamese War

See also: Cambodian humanitarian crisis

On 10 January 1979, after the Vietnamese army and the KUFNS (Kampuchean United Front for National Salvation) invaded Cambodia and overthrowing the Khmer Rouge, the new People's Republic of Kampuchea (PRK) was established with Heng Samrin as head of state. Pol Pot's Khmer Rouge forces retreated rapidly to the jungles near the Thai border. The Khmer Rouge and the PRK began a costly struggle that played into the hands of the larger powers China, the United States and the Soviet Union. The Khmer People’s Revolutionary Party’s rule gave rise to a guerrilla movement of three major resistance groups – the FUNCINPEC (Front Uni National pour un Cambodge Indépendant, Neutre, Pacifique, et Coopératif), the KPLNF (Khmer People’s National Liberation Front) and the PDK ( Party of Democratic Kampuchea, the Khmer Rouge under the nominal presidency of Khieu Samphan).^[147] "All held dissenting perceptions concerning the purposes and modalities of Cambodia’s future". Civil war displaced 600,000 Cambodians, who fled to refugee camps along the border to Thailand and tens of thousands of people were murdered throughout the country.^{[148][149][150]}

Peace efforts began in Paris in 1989 under the State of Cambodia, culminating two years later in October 1991 in a comprehensive peace settlement. The United Nations was given a mandate to enforce a ceasefire, and deal with refugees and disarmament known as the United Nations Transitional Authority in Cambodia (UNTAC).^[151]