The Third Indochina War was a series of interconnected armed conflicts, mainly among the various communist factions over strategic influence in Indochina after Communist victory in South Vietnam, Laos, and Cambodia in 1975. The conflict primarily started due to continued raids and incursions by the Khmer Rouge into Vietnamese territory that they sought to retake. These incursions would result in the Cambodian–Vietnamese War in which the newly unified Vietnam overthrew the Pol Pot regime and the Khmer Rouge, in turn ending the Cambodian genocide. Vietnam had installed a government led by many opponents of Pol Pot, most notably Hun Sen, a former Khmer Rouge commander. This led to Vietnam's occupation of Cambodia for over a decade. The Vietnamese push to completely destroy the Khmer Rouge led to them conducting border raids in Thailand against those who had provided sanctuary. China strongly objected to the invasion of Cambodia. Chinese armed forces launched a punitive operation (Sino-Vietnamese War) in February 1979 and attacked Vietnam's northern provinces, determined to contain Soviet/Vietnamese influence and prevent territorial gains in the region. In order to acquire full control over Cambodia the People's Army of Vietnam needed to dislodge the remaining Khmer Rouge leaders and units, which had retreated to the remote areas along the Thai-Cambodian border. After the Paris Peace Conference in 1989, the PAVN withdrew from Cambodian territory. Finally regular troop engagements in the region ended after the conclusion of the 1991 Paris Peace Accords. In Laos, an insurgency is still ongoing, though to a lesser extent since 2007, with the government being supported by both China and Vietnam.

Background

Soviet-Chinese discord

After Joseph Stalin's death in 1953, Nikita Khrushchev became leader of the Soviet Union. His denouncement of Stalin and his purges, the introduction of more moderate communist policies and foreign policy of peaceful coexistence with the West angered China's leadership. Mao Zedong had been following a strict Stalinistic course, that insisted on the cult of personality as a unifying force of the nation. Disagreements over technical assistance for developing China's nuclear weapons and basic economic policies further alienated the Soviets and the Chinese as opposing forces of communist influence across the globe. As decolonization movements began to pick up speed in the 1960s and many such countries descended into violence, both of the communist powers competed for political control of the various nations or competing factions in ongoing civil war fights. Ever more diverging Chinese and Soviet strategic and political doctrines had increased the Sino-Soviet split of the mid-1950s.

Political developments during the Vietnam War

<!-- EDITORIAL NOTE: Meanwhile in Indochina, since 1952 American Forces had been fighting against the communist [Democratic Republic of Vietnam](https://bliptext.com/articles/democratic-republic-of-vietnam), which was secured in the North of the country, while it supported the anti-communist [Republic of Vietnam](https://bliptext.com/articles/republic-of-vietnam). This fighting often spilt over into Vietnam's neighbours, especially as the [John F. Kennedy](https://bliptext.com/articles/john-f-kennedy)'s administration began U.S. involvement in the war proper, and as the [Richard Nixon](https://bliptext.com/articles/richard-nixon)'s administration tried to escalate the war in its later stages. This escalation led to the destabilisation of Vietnamese neighbours. As the Vietnam War progressed, American involvement lessened, and by 1975 American troops had completely left the country. This allowed the communist Vietnamese to enter Saigon largely unopposed and declared themselves the sole government of Vietnam. While at first closer to the Chinese, due to assistance during the war and general closeness, the government soon drifted apart, due to ideological differences, and pressures from Russia. === Cambodia === After the 1954 [Geneva Conference](https://bliptext.com/articles/geneva-conference-1954), Cambodia restored its monarchy under the authoritarian and isolationist regime of Prince Norodom Sihanouk, who sought to be neutral as the region descended into violence. Cambodia, however, descended into political violence further in 1968 after a group of Maoist-influenced rebels rose up in the nation and began an insurgency against the royalist forces, led by [Pol Pot](https://bliptext.com/articles/pol-pot) and calling themselves the [Khmer Rouge](https://bliptext.com/articles/khmer-rouge). During this time, Vietnamese forces, under attack by U.S. troops, fled into Cambodia, expanding the Ho Chi Minh Trail into the nation, and established camps to continue the war on a front with South Vietnam. Sihanouk saw these forces as equal threats against his rule and began a brutal campaign against all communist forces in the country, especially in the northeast. The U.S. meanwhile began to view Sihanouk as more and more of a threat to the ongoing war efforts in the region. This is because during the opening stages of the Khmer Rouge insurgency Sihanouk had cut off diplomatic relations with America, and his movement into the northeast had caused [ARVN](https://bliptext.com/articles/arvn) advisors to begin fearing of a Cambodian invasion. As a result, America began a bombing campaign into Cambodia. The bombing, and the subsequent invasion by the U.S. military and destabilised the nation. In 1970, a U.S. backed coup ousted Sihanouk and established the Khmer Republic. Though initially liked by the elite of Cambodia, the republic became more and more dictatorial as the war against the Khmer Rouge continued. During this time, America continued its bombing campaign against Cambodia, leading to huge amounts of civilian deaths. The Khmer Rouge used the campaign as recruiting material for the largely ignored and angry peasantry of Cambodia. The Khmer Rouge also started to centralise around [Pol Pot](https://bliptext.com/articles/pol-pot), who took power in 1962. Pot took the opportunity to purge the party, and the party became increasingly focused around the worship of Pol Pot. The Khmer Republic fell in April 1975, when the Khmer Rouge entered Phnom Penh, and ousted the Republican government, officially declaring allegiance to Pol Pot.-->

The Democratic Republic of Vietnam (North Vietnam), which had chosen to ally with the USSR, justified incursions into neighbouring Laos and Cambodia during the Second Indochinese War by reference to the international nature of communist revolution, where "Indochina is a single strategic unit, a single battlefield" and the Vietnam People's Army's pivotal role in bringing this about. However, this internationalism was obstructed by complicated regional historical realities, such as the "timeless oppositions between the Chinese and the Vietnamese on the one hand and the Vietnamese and the Khmers on the other". North Vietnam intervened in the civil war between the Royal Lao Army and the communist Pathet Lao until the establishment of the Lao People's Democratic Republic and the "Treaty of Friendship and Cooperation" signed in July 1977. Permanently stationed North Vietnamese troops secured and maintained vital supply routes and strategic staging sites (Ho Chi Minh trail). From 1958 on, Northern and Southern Vietnamese combat troops also began to infiltrate the remote jungles of eastern Cambodia where they continued the Ho Chi Minh trail. The Cambodian communist insurgents had joined these sanctuaries during the late 1960s. Although co-operation took place, the Khmer communists did not adopt modern socialist doctrines and eventually allied with China. The complete American withdrawal instantaneously eliminated the principal and common adversary of all the communist powers. The communist regimes of Cambodia, Vietnam and Laos pledged allegiance with one of these two opposing factions.

Cambodian-Vietnamese war

After the Fall of Saigon and Phnom Penh in April and May 1975 and the subsequent communist takeover in Laos five months later, Indochina was dominated by communist regimes. Armed border clashes between Cambodia and Vietnam soon flared up and escalated as Khmer Rouge forces advanced deep into Vietnamese territory and raided villages, killing hundreds of civilians. Vietnam counterattacked and in December 1978, NVA troops invaded Cambodia, reaching Phnom Penh in January 1979 and arriving at the Thai border in spring 1979. However, as China, the U.S. and the majority of the international community opposed the Vietnamese campaign, the remaining Khmer Rouge managed to permanently settle in the Thai-Cambodian border region. In a United Nations Security Council meeting, seven non-aligned members drafted a resolution for a ceasefire and Vietnamese withdrawal which failed due to opposition from the Soviet Union and Czechoslovakia. Thailand tolerated the presence of the Khmer Rouge on its soil as they helped to contain the Vietnamese and Thai domestic guerillas. Over the course of the following decade, the Khmer Rouge received considerable support from Vietnam's enemies and served as a bargaining tool in the Realpolitik of Thailand, China, the ASEAN and the U.S.

Vietnamese-Thailand conflict

Khmer Rouge forces operated from inside Thai territory attacking the pro-Hanoi People's Republic of Kampuchea's government. Similarly Vietnamese forces frequently attacked the Khmer Rouge bases inside Thailand. Eventually Thai and Vietnamese regular troops clashed on several occasions during the following decade. The situation escalated as Thailand's territorial sovereignty was violated on numerous occasions. Heavy fighting with many casualties resulted from direct confrontations between Vietnamese and Thai troops. Thailand increased troop strength, purchased new equipment and built a diplomatic front against Vietnam.

Sino-Vietnamese conflicts

China attacked Vietnam in response to Vietnam's occupation of Cambodia, entered northern Vietnam and captured several cities near the border. On March 6, 1979, China declared that their punitive mission had been successful and withdrew from Vietnam. However, both China and Vietnam claimed victory. The fact that Vietnamese forces continued to stay in Cambodia for another decade implies that China's campaign was a strategic failure. On the other hand, the conflict had proven that China had succeeded in preventing effective Soviet support for its Vietnamese ally. As forces remained mobilized, the Vietnamese Army and the Chinese People's Liberation Army engaged in another decade-long series of border disputes and naval clashes that lasted until 1990. These mostly local engagements usually wore out in prolonged stand-offs, as neither side achieved any long-term military gains. By the late 1980s the Vietnamese Communist Party's (VCP) began to adopt its Doi Moi (renovation) policy and reconsider its China policy in particular. Prolonged hostile relations with China had been recognized as to be detrimental to economic reforms, national security and the regime's survival. A number of political concessions opened the way for the normalization process of 1991.

Regional conflicts