Communist guerrilla organization operating in South Vietnam (1960–75). Opposition to the Saigon-based regime of Ngo Dinh Diem had already produced widespread guerrilla activity in South Vietnam when communist interests founded the National Front for the Liberation of South Vietnam (known to its opponents as the Vietcong) in 1960. As US military support for the Saigon government broadened into the full-scale Vietnam War so Vietcong forces were supplied with arms and supported by North Vietnamese forces brought to the south via the Ho Chi Minh Trail, which passed through neighbouring Laos and Cambodia. They maintained intensive guerrilla operations, and occasionally fought large set-piece battles. They finally undermined both US support for the war and the morale of the South Vietnamese army and opened the way for communist triumph and the reunification of Vietnam in 1975.