Quick questions on Vietnamese invasion of Cambodia and end of conflict 1978-1979: HSC Modern History Indochina

Democratic Kampuchea, from 1977 onwards, claimed the Mekong Delta as Cambodian territory and launched a series of cross-border raids into Vietnam. Khmer Rouge units massacred Vietnamese civilians in An Giang, Tay Ninh, and Kien Giang Provinces. The Ba Chuc massacre (18 April 1978) killed around 3,157 Vietnamese civilians (only two survivors). Ethnic Vietnamese inside Cambodia were expelled or killed; around 150,000 fled in 1977 to 1978.

The Politburo in Hanoi made the decision to invade Cambodia in late 1978. Pre-invasion preparations included the Treaty of Friendship and Cooperation between Vietnam and the USSR (Moscow, 3 November 1978), which obliged the parties to consult in the event of attack. This was the explicit Soviet umbrella against a Chinese response.

Vietnamese forces invaded Cambodia on 25 December 1978 with around 150,000 troops in 13 divisions. The campaign was conventional and rapid. Khmer Rouge defences collapsed across multiple axes. The Vietnamese armoured columns took:

The People's Republic of Kampuchea was proclaimed on 8 January 1979. Heng Samrin served as President of the People's Revolutionary Council; Pen Sovan was Prime Minister, later replaced by Chan Sy and then Hun Sen (Prime Minister from 1985 onwards). Vietnam stationed around 200,000 troops in Cambodia. Vietnamese advisers ran the ministries.

Deng Xiaoping, on his February 1979 visit to the United States, told Carter that he would "teach Vietnam a lesson". The PRC launched its punitive invasion on 17 February 1979.

The Cambodian civil war continued through the 1980s. The Coalition Government of Democratic Kampuchea (CGDK), formed on 22 June 1982, comprised: - the Khmer Rouge under Khieu Samphan (largest force, around 35,000), - the National United Front for an Independent, Neutral, Peaceful and Cooperative Cambodia (FUNCINPEC) under Sihanouk, - the Khmer People's National Liberation Front under Son Sann.

Stephen Morris (Why Vietnam Invaded Cambodia, 1999) on the politics of the 1978 decision.

The civil war continued through the 1980s and ended formally only in 1991 to 1993.

The 3 November 1978 Treaty was the precondition for Vietnam's decision to invade.

17 February 1979, not at the time of the Cambodian invasion.