High Quality Content by WIKIPEDIA articles! The Cambodian–Vietnamese War was an armed conflict between the Socialist Republic of Vietnam and Democratic Kampuchea. The war began with isolated clashes along the land and maritime boundaries of Vietnam and Kampuchea between 1975 and 1977, occasionally involving division-sized military formations. On 25 December 1978, Vietnam launched a full-scale invasion of Kampuchea and subsequently occupied the country after the Khmer Rouge was removed from power.