Cambodian-Vietnamese Conflict, 1977-1991

The Cambodian–Vietnamese War was an armed conflict from 1978 to 1989 between Democratic Kampuchea and the Socialist Republic of Vietnam, and their respective allies. It began in December 1978, with a Vietnamese invasion of Cambodia which toppled the Khmer Rouge regime and ended in 1989 with the withdrawal of Vietnamese forces from Cambodia. This Cold War conflict was part of the Third Indochina War and Sino-Soviet split with the Soviet Union supporting Vietnam and China supporting Kampuchea. Despite both being communist, the alliance between the Communist Party of Vietnam and the Khmer Rouge broke down after both defeated Vietnamese and Cambodian anti-communist regimes respectively in the Second Indochina War. As a result, the war was preceded by years of conflict between Vietnam and the Khmer Rouge, led by Pol Pot, when the Khmer Rouge-ruled Democratic Kampuchea repeatedly invaded Vietnam, including massacres by the Khmer Rouge, notably the Ba Chúc massacre of over 3,000 Vietnamese civilians in April 1978. On 21 December 1978, the Vietnamese launched a limited offensive towards the town of Kratie. On 23 December 1978, 10 out of 19 divisions of the Khmer Rouge's Kampuchea Revolutionary Army opened fire along the border with Vietnam with the goal of invading the southwestern border provinces of Đồng Tháp, An Giang and Kiên Giang. On 25 December 1978, Vietnam supported Cambodian dissidents in exile and launched a full-scale invasion of Kampuchea, occupying the country in two weeks, capturing the capital Phnom Penh, and removing the Khmer Rouge government of the Communist Party of Kampuchea from power. In doing so, Vietnam put an ultimate stop to the Cambodian genocide which had killed between 1.2 and 2.8 million people or between 13 and 30 percent of the country's population since 1975. However, the Khmer Rouge regime maintained its membership in the United Nations and the war isolated Vietnam from the international community except the Eastern Bloc. The Vietnamese occupation caused discontent among Cambodians. After the Cambodian capital was captured by the Vietnamese, another communist state was established to replace the old regime while the Khmer Rouge was forced to retreat into the jungle near the border with Thailand where the Khmer Rouge alongside the Khmer People's National Liberation Front, led by Son Sann, and FUNCINPEC, led by former king Norodom Sihanouk, continued to fight the Vietnamese army and the pro-Vietnamese Cambodian government. In 1982, they formed the Coalition Government of Democratic Kampuchea. Vietnam's goal of defeating the Khmer Rouge remnants could not be achieved while domestic difficulties forced Vietnam to gradually withdraw its troops. The Vietnamese army completely withdrew in September 1989, and in 1991 the Paris Peace Agreements were signed to open the process of reconciliation between Cambodia's factions, leading to a UN-led transition and the restoration of multi-party rule and a constitutional monarchy in the Kingdom of Cambodia in September 1993.