Ho Chi Minh trail in the context of "Cambodia (1953–1970)"

The Vietnam War (1 November 1955 – 30 April 1975) was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam was supported by the Soviet Union and China, while South Vietnam was supported by the United States and other anti-communist nations. The conflict was the second of the Indochina wars and a proxy war of the Cold War between the Soviet Union and US. The Vietnam War was one of the postcolonial wars of national liberation, a theater in the Cold War, and a civil war, with civil warfare a defining feature from the outset. Direct US military involvement escalated from 1965 until its withdrawal in 1973. The fighting spilled into the Laotian and Cambodian Civil Wars, which ended with all three countries becoming communist in 1975.

After the defeat of the French Union in the First Indochina War that began in 1946, Vietnam gained independence in the 1954 Geneva Conference but was divided in two at the 17th parallel: the Viet Minh, led by Ho Chi Minh, took control of North Vietnam, while the US assumed financial and military support for South Vietnam, led by Ngo Dinh Diem. The North Vietnamese supplied and directed the Viet Cong (VC), a common front of dissidents in the south which intensified a guerrilla war from 1957. In 1958, North Vietnam invaded Laos, establishing the Ho Chi Minh trail to supply the VC. By 1963, the north had covertly sent 40,000 soldiers of its People's Army of Vietnam (PAVN), armed with Soviet and Chinese weapons, to fight in the insurgency in the south. President John F. Kennedy increased US involvement from 900 military advisors in 1960 to 16,000 in 1963 and sent more aid to the Army of the Republic of Vietnam (ARVN), which failed to produce results. In 1963, Diem was killed in a US-backed military coup, which added to the south's instability.

The Viet Cong (VC) was an epithet and umbrella term to refer to the communist-driven armed movement and united front organization in South Vietnam. It was formally organized as and led by the National Liberation Front of South Vietnam, and conducted military operations under the name of the Liberation Army of South Vietnam (LASV). The movement fought under the direction of North Vietnam against the South Vietnamese and United States governments during the Vietnam War. The organization had both guerrilla and regular army units, as well as a network of cadres who organized and mobilized peasants in the territory the VC controlled. During the war, communist fighters and some anti-war activists claimed that the VC was an insurgency indigenous to the South that represented the legitimate rights of people in South Vietnam, while the U.S. and South Vietnamese governments portrayed the group as a tool of North Vietnam. It was later conceded by the modern Vietnamese communist leadership that the movement was actually under the North Vietnamese political and military leadership, aiming to unify Vietnam under a single banner.

North Vietnam established the National Liberation Front (NLF) on December 20, 1960, at Tân Lập village in Tây Ninh Province to foment insurgency in the South. Many of the VC's core members were volunteer "regroupees", southern Viet Minh who had resettled in the North after the Geneva Accord (1954). Hanoi gave the regroupees military training and sent them back to the South along the Ho Chi Minh trail in the late 1950s and early 1960s. The VC called for the unification of Vietnam and the overthrow of the American-backed South Vietnamese government. The VC's best-known action was the Tet Offensive, an assault on more than 100 South Vietnamese urban centers in 1968, including an attack on the U.S. embassy in Saigon. The offensive riveted the attention of the world's media for weeks, but also overextended the VC. Later communist offensives were conducted predominantly by the North Vietnamese. The organization officially merged with the Fatherland Front of Vietnam on February 4, 1977, after North and South Vietnam were officially unified under a communist government.