The Cambodian Civil War was a conflict that pitted the forces of the Communist Party of Kampuchea (known as the Khmer Rouge) and their allies the Democratic Republic of Vietnam (North Vietnam) and the Viet Cong against the government forces of Cambodia (after October 1970, the Khmer Republic), which were supported by the United States (U.S.) and the Republic of Vietnam (South Vietnam). After five years of savage fighting, the Republican government was defeated on 17 April 1975 when the victorious Khmer Rouge proclaimed the establishment of Democratic Kampuchea.