Claim: The United States took part in the Vietnam War to prevent communist takeover of South Vietnam.

The Indochina Wars -LRB- Chiến tranh Đông Dương -RRB- were a series of wars fought in Southeast Asia from 1946 until 1989 , between communist Indochinese forces against mainly French , South Vietnamese , American , Cambodian , Laotian and Chinese forces . The term `` Indochina '' originally referred to French Indochina , which included the current states of Vietnam , Laos and Cambodia . , it applies largely to a geographic region , rather than to a political area . The wars included :  The First Indochina War -LRB- called the Indochina War in France and the French War in Vietnam -RRB- began after the end of World War II in 1945 and lasted until the French defeat in 1954 . After a long campaign of resistance against the French and the Japanese , Viet Minh forces had claimed a victory -LRB- the August Revolution -RRB- after Japanese and Vichy French forces surrendered in the North on 15 August 1945 . In the War in Vietnam -LRB- 1945 -- 46 -RRB- , British forces temporarily occupied the South , starting from 13 September 1945 , only to restore French colonial control in 1946 . In the United Nations and through their alliance with the United Kingdom and the United States , the French demanded return of their former Indochina colony prior to agreeing to participate in the NATO alliance -LRB- founded in 1949 -RRB- opposing Soviet expansion beyond the countries of the Warsaw Pact -LRB- founded in 1955 -RRB- in the Cold War . The communist/nationalist Viet Minh , whom the Allies had supported during the war , continued fighting the French with support from China and the Soviet Union , ultimately forcing the NATO-backed French out of Indochina -LRB- 1954 -RRB- .  The Second Indochina War -LRB- called the Vietnam War in the West or the American War in Vietnam -RRB- began as a conflict between the United States-backed South Vietnamese government and its opponents , both the North Vietnamese-based communist Viet Cong -LRB- National Liberation Front -RRB- and the People 's Army of Vietnam -LRB- PAVN -RRB- , known in the West as the North Vietnamese Army -LRB- NVA -RRB- . The conflict began in the late 1950s and lasted until 1975 when the North Vietnamese conquered South Vietnam . The United States , which had supported France during the first Indochina war , backed the South Vietnam government in opposition to the National Liberation Front and the Communist-allied NVA . The North benefited from military and financial support from China and the Soviet Union , members of the Communist bloc . Fighting also occurred during this time in Cambodia between the US-backed government , the NVA , and the Communist-backed Khmer Rouge -LRB- known as the Cambodian Civil War , 1967 -- 1975 -RRB- and in Laos between the US-backed government , the NVA , and the Communist-backed Pathet Lao -LRB- known as the Laotian Civil War or Secret War , 1962 -- 1975 -RRB- .   The Third Indochina War was a period of prolonged conflict following the Vietnam War , in which several wars were fought :   The Cambodian -- Vietnamese War began when Vietnam invaded Cambodia and deposed the genocidal Khmer Rouge régime . The war lasted from May 1975 to December 1989 .   The Sino-Vietnamese War was a short war fought in February -- March 1979 between the People 's Republic of China and the Socialist Republic of Vietnam . The Chinese launched a Punitive expedition in revenge for the Vietnamese invasion of Cambodia , and withdrew a month later to prewar positions . Skirmishes along the border would continue until 1990 .   After the triumph of the Pathet Lao , an anti-communist insurgency in Laos lasted until most Hmong insurgents surrendered in 2007 , though some resistance cells remain active . Thailand , which supported the Lao insurgents , as well as the anti-Vietnamese forces in the Third Indochina War , fought a few skirmishes with Vietnam in 1984 , and a short conflict with Laos in 1987 .   The Communist Party of Thailand fought an insurgency from 1965-1989 . They received backing from Laos and Vietnam from 1975-1979 , however were expelled from their bases and lost most of their supply lines after they sided with the Cambodian-Chinese aligned forces , rather than the pro-Soviet Vietnamese and Laotian regimes .