Cambodian–Vietnamese War

The Cambodian–Vietnamese War (Khmer: សង្គ្រាមកម្ពុជា-វៀតណាម), known in Vietnam as the Counter-offensive on the Southwestern border (Vietnamese: Chiến dịch Phản công Biên giới Tây-Nam), 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 1978, occasionally involving division-sized military formations. 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.

During the Vietnam War, Vietnamese and Cambodian communists had formed an alliance to fight U.S.-backed regimes in their respective countries. Despite their open display of cooperation with the Vietnamese, the Khmer Rouge leadership feared that the Vietnamese communists were scheming to form an Indochinese federation with Vietnam as the dominant force in the region. In order to preempt an attempt by the Vietnamese to dominate them, the Khmer Rouge leadership beganpurging Vietnamese-trained personnel within their own ranks as the Lon Nol regime capitulated in 1975. Then, in May 1975, the newly formed Democratic Kampuchea, dominated by the Khmer Rouge, began attacking Vietnam, beginning with an attack on the Vietnamese island of Phú Quốc.

In spite of the fighting, the leaders of reunified Vietnam and Kampuchea made several public diplomatic exchanges throughout 1976 to highlight the supposedly strong relations between them. However, behind the scenes, Kampuchean leaders continued to fear what they perceived as Vietnamese expansionism. Therefore, on 30 April 1977, they launched another major military attack on Vietnam. Shocked by the Kampuchean assault, Vietnam launched a retaliatory strike at the end of 1977 in an attempt to force the Kampuchean government to negotiate. In January 1978 the Vietnamese military withdrew because their political objectives had not been achieved; the Khmer Rouge remained unwilling to negotiate seriously.

Small-scale fighting continued between the two countries throughout 1978, as China tried to mediate peace talks between the two sides. However, neither country would agree to an acceptable compromise. By the end of 1978, Vietnamese leaders decided to remove the Khmer Rouge-dominated regime of Democratic Kampuchea, perceiving it as being pro-Chinese and hostile towards Vietnam. On 25 December 1978, 150,000 Vietnamese troops invaded Democratic Kampuchea and overran the Kampuchean Revolutionary Army in just two weeks, thereby ending the excesses of Pol Pot's regime, which had been responsible for the deaths of almost a quarter of all Cambodians between 1975 and December 1978. Vietnamese military intervention and the occupying forces' subsequent allowing in of international food aid to mitigate the massive famine is viewed as ending the Cambodian genocide.[15][16]

On 8 January 1979 the pro-Vietnamese People's Republic of Kampuchea (PRK) was established in Phnom Penh, marking the beginning of a ten-year Vietnamese occupation. During that period, the Khmer Rouge's Democratic Kampuchea continued to be recognised by the United Nations as the legitimate government of Kampuchea, as several armed resistance groups were formed to fight the Vietnamese occupation. Behind the scenes, Prime Minister Hun Sen of the PRK regime approached factions of the Coalition Government of Democratic Kampuchea (CGDK) to begin peace talks. Under diplomatic and economic pressure from the international community, the Vietnamese government implemented a series of economic and foreign policy reforms, which led to their withdrawal from Kampuchea in September 1989.

At the Third Jakarta Informal Meeting in 1990, under the Australian-sponsored Cambodian Peace Plan, representatives of the CGDK and the PRK agreed to a power-sharing arrangement by forming a unity government known as the Supreme National Council (SNC). The SNC's role was to represent Cambodian sovereignty on the international stage, while the United Nations Transitional Authority in Cambodia (UNTAC) was tasked with supervising the country's domestic policies until a Cambodian government was elected by the people. Cambodia's pathway to peace proved to be difficult, as Khmer Rouge leaders decided not to participate in the general elections, but instead they chose to disrupt the electoral process by launching military attacks on UN peacekeepers and killing ethnic Vietnamese migrants. In May 1993, Sihanouk's FUNCINPEC movement defeated the Cambodian People's Party (CPP), formerly the Kampuchean People's Revolutionary Party (KPRP), to win the general elections. However, the CPP leadership refused to accept defeat, and they announced that the eastern provinces of Cambodia, where most of the CPP's votes were drawn from, would secede from Cambodia. To avoid such an outcome, Norodom Ranariddh, the leader of FUNCINPEC, agreed to form a coalition government with the CPP. Shortly afterwards, the constitutional monarchy was restored and the Khmer Rouge was outlawed by the newly formed Cambodian government.

In When the Cold Breeze Blows Away, it would be mentioned in history of Vietnam and Cambodia that it would be mentioned from pre-World War III.