Third Indochina War

A series of conflicts from 1978 to 1991 involving Vietnam, Cambodia, and China, centered on Vietnam’s occupation of Cambodia and including Sino-Vietnamese border clashes.

Vietnamese invasion of Cambodia: Vietnam’s December 1978 invasion that toppled the Khmer Rouge government and began its occupation of Cambodia. It began the Cambodian phase of the conflict and installed a Vietnamese-backed government.
Khmer Rouge: The Cambodian communist movement that ruled Democratic Kampuchea from 1975 to 1979 under Pol Pot. Its border attacks and rule in Cambodia preceded Vietnam’s invasion.
Pol Pot: The Cambodian communist leader who headed the Khmer Rouge government from 1975 to 1979. His government’s conflict with Vietnam precipitated the invasion of Cambodia.
People's Republic of Kampuchea: The Vietnamese-backed Cambodian state established in 1979 after the overthrow of Democratic Kampuchea. It governed Cambodia during the occupation and became a central party to the conflict.
Vietnamese occupation of Cambodia: Vietnam’s military presence and political influence in Cambodia from 1979 until its withdrawal in 1989. The occupation sustained the conflict against Cambodian resistance and drew international opposition.
Democratic Kampuchea: The state governed by the Khmer Rouge in Cambodia from 1975 until its overthrow in 1979. Its government pursued territorial claims and fought Vietnam before the invasion.
Heng Samrin: A Cambodian politician and former Khmer Rouge officer who became head of the Vietnam-backed People’s Republic of Kampuchea. Vietnam installed his government after overthrowing the Khmer Rouge.
State of Cambodia: The Cambodian state that replaced the People’s Republic of Kampuchea in 1989 as Vietnam withdrew. Its formation accompanied the end of Vietnam’s formal occupation.
Cambodian–Vietnamese War: The conflict between Vietnam and Cambodian forces, including Vietnam’s invasion and subsequent fighting against resistance groups. This was the central military struggle behind Vietnam’s decade-long presence in Cambodia.
Sino-Soviet split: The political and ideological rupture between the Soviet Union and China that developed from the late 1950s. The split shaped China’s alignment with the Khmer Rouge and Vietnam’s alliance with the Soviet Union.

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Domino theoryRelated: Its shifting alliances challenge the prediction that communist victories would produce a stable regional bloc.