Survivors sift through rubble after the Khmer Rouge bombed Phnom Penh, the capital city (1975)
The civil war was fought between the National United Front of Kampuchea and the Kingdom of Cambodia (which later became the Khmer Republic). The Khmer Republic had the backing of the United States and the South Vietnamese, while the National United Front of Kampuchea had the backing of the North Vietnamese communist alliance. The war was considered a branch of the Vietnam War (1959-1975). The Khmer Republic was defeated and the Khmer Rouge established the Democratic Kampuchea when Phnom Penh fell.