Vietnam War: Anti-war protesters in Washington, D.C. stage a symbolic March Against Death.

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.

Opposition to United States involvement in the Vietnam War began in 1965 with demonstrations against the escalating role of the United States in the war. Over the next several years, these demonstrations grew into a social movement which was incorporated into the broader counterculture of the 1960s.