Vietnam war refers to the US political and military continuation of the French Campaign in Indochina that followed the signing of the 1954 Geneva agreements, which divided Vietnam along the 17th Parallel, and which ended when the People's Army of Vietnam (PAVN) occupied Saigon on 30 April 1975. A continuation of the Vietminh's effort to free Vietnam from foreign domination, this isolated conflict was slowly transformed into the bloodiest battleground of the Cold War.

Following the Genesva accords, relative calm descended on Vietnam. In Hanoi, the Vietminh, who had come under the control of the Vietnamese Lao Dong (Communist) Party by the time of the French defeat, consolidated their power under the leadership of Ho Chi Minh, collectivized agriculture in the north (which sparked a bloodily suppressed peasant uprising in 1956), and debated how to gain control of South Vietnam. In Saigon Bao Dai, the French-backed emperor, was deposed in a referendum by the US-supported Ngo Dinh Diem in late 1955. Diem, a Catholic in a predominantly Buddhist country, was a committed anti-communist. Bolstered by increasing economic and covert aid from the USA, Diem launched an anti-communist sweep of South Vietnam. By the late 1950s, the hard-pressed Vietminh cadres who had remained in the South, derisively dubbed Vietcong by Diem, appealed to Hanoi for reinforcement and greater support.

Although Hanoi had ordered the formation of Vietcong military units in the Mekong Delta as early as 1957, North Vietnamese leaders debated if the time was ripe to intervene more directly in the South. At a May 1959 meeting of the Lao Dong Party, they decided to support ‘armed revolution’ against Saigon: 4, 500 ‘regroupees’ (a southern communist cadre who had come to North Vietnam following the Geneva accords) began to stream down the ‘Ho Chi Minh Trail’ between North and South Vietnam to help form Vietcong units. In December 1960, Hanoi announced the creation of the National Liberation Front (NLF), a collection of southern groups opposing the Diem regime, to bolster the North Vietnamese contention that the revolt against Saigon was an indigenous movement.