The Viet Cong was an epithet and umbrella term to call the communist-driven armed movement and united front organization in South Vietnam, Laos and Cambodia. Formally organized as and led by the National Liberation Front of South Vietnam, it 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 Viet Cong controlled. During the war, communist fighters and some anti-war activists claimed that the Viet Cong 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.

The Tet Offensive was a major escalation and one of the largest military campaigns of the Vietnam War. The Viet Cong (VC) and North Vietnamese People's Army of Vietnam (PAVN) launched a surprise attack on January 30, 1968 against the forces of the South Vietnamese Army of the Republic of Vietnam (ARVN), the United States Armed Forces and their allies. It was a campaign of surprise attacks against military and civilian command and control centers throughout South Vietnam. The name is the truncated version of the Lunar New Year festival name in Vietnamese, Tết Nguyên Đán, with the offense chosen during a holiday period as most ARVN personnel were on leave. The purpose of the wide-scale offensive by the Hanoi Politburo was to trigger political instability in a belief that mass armed assault on urban centers would trigger defections and rebellions.