The Cambodian–Vietnamese War (, ), known in Vietnam as the Counter-offensive on the Southwestern border (), and by Cambodian nationalists as the Vietnamese invasion of Cambodia (), was an armed conflict between Democratic Kampuchea, controlled by the Khmer Rouge, and the Socialist Republic of Vietnam. The war began with repeated attacks by the Kampuchean Revolutionary Army on the southwestern border of Vietnam, particularly the Ba Chuc massacre which resulted in the deaths of over 3,000 Vietnamese civilians. On 25 December 1978, Vietnam launched a full-scale invasion of Kampuchea, and subsequently occupied the country and removed the government of the Communist Party of Kampuchea from power.