Vietnam War: American warships begin the first bombardment of National Liberation Front targets within South Vietnam.

The Vietnam War was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam and South 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.

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.

South Vietnam, officially the Republic of Vietnam, was a country in Southeast Asia that existed from 1955 to 1975. It first garnered international recognition in 1949 as the associated State of Vietnam within the French Union, with its capital at Saigon. Since 1950, it was a member of the Western Bloc during the Cold War. Following the 1954 partition of Vietnam, it became known as South Vietnam and was established as a republic in 1955. South Vietnam was bordered by North Vietnam to the north, Laos to the northwest, Cambodia to the southwest, and Thailand across the Gulf of Thailand to the southwest. Its sovereignty was recognized by the United States and 87 other nations, though it failed to gain admission into the United Nations as a result of a Soviet veto in 1957. It was succeeded by the Republic of South Vietnam in 1975. In 1976, the Republic of South Vietnam and North Vietnam merged to form the Socialist Republic of Vietnam.