Political map of East Asia and the Western Pacific 5 March 1979 (Sino-Vietnamese War): The Khmer Rouge's brutal rule in Cambodia led to millions of deaths (Cambodian genocide), while its growing antagonism with its former Vietnamese allies erupted into full scale war in 1978. Vietnam quickly occupied most of Cambodia (Vietnamese invasion of Cambodia), prompting China, which had supported the Khmer Rouge, to attack Vietnam (Sino-Vietnamese War). After a month of brutal but inconclusive warfare, the Chinese withdrew.