The Sino-Vietnamese War (also known by other names) was a war which occurred in early 1979 between China and Vietnam. China launched an offensive ostensibly in response to Vietnam's invasion and occupation of Cambodia in 1978, which ended the rule of the Khmer Rouge. The conflict lasted for about a month, with China withdrawing its troops in March 1979.
In February 1979, Chinese forces launched a surprise invasion of northern Vietnam and quickly captured several cities near the border. On 6 March of that year, China declared that its punitive mission had been accomplished. Chinese troops then withdrew from Vietnam. Vietnam continued to occupy Cambodia until 1989, suggesting that China failed to achieve one of its stated aims of dissuading Vietnam from involvement in Cambodia. China's operation at least forced Vietnam to withdraw the 2nd Corps from the invasion forces of Cambodia to reinforce the defense of Hanoi. Additionally, it demonstrated that the Soviet Union, China's Cold War communist adversary, was unable to protect its Vietnamese ally. The conflict had a lasting impact on the relationship between China and Vietnam, and diplomatic relations between the two countries were not fully restored until 1991, following the withdrawal of Vietnamese troops from Cambodia and the dissolution of the Soviet Union.
The Sino-Vietnamese land border was formally agreed upon in 1999.
The Sino-Vietnamese War is known by various names in Chinese and Vietnamese. The neutral names for the war are 中越战争 (Sino-Vietnamese war) in Chinese and "Chiến tranh biên giới Việt-Trung" (Vietnamese-Chinese border war) in Vietnamese. The Chinese government refers to the war as the "China-Vietnam border self-defense counterattack operations" (中越边境自卫还击作战) or the "Self-defensive counterattack operations against Vietnam to protect the border" (对越自卫还击保卫边疆作战).
Chinese non-official sources generally use a shorter form, "Self-defensive counterattack against Vietnam" (对越自卫反击战).
The Vietnamese Government and Communist Party generally calls it the "Northern Frontier Defense War" (Chiến tranh Bảo vệ Biên giới phía Bắc).
The Sino-Vietnamese War is also known as the Third Indochina War in Western historiography.
Just as the First Indochina War—which emerged from the complex situation following World War II—and the Vietnam War arose from the indecisive aftermath of political relations, the Third Indochina War again followed the unresolved problems of the earlier wars.
The Chinese Communist Party and the Viet Minh had a long history. During the initial stages of the First Indochina War with France, the recently founded communist China continued the Soviet mission to expand communism. Therefore, they aided the Viet Minh and became the connector between Soviets and the Viet Minh.
After the death of Joseph Stalin in March 1953, relations between the Soviet Union and China began to deteriorate. Mao Zedong believed the new Soviet leader Khrushchev had made a serious error in his Secret Speech denouncing Stalin in February 1956, and criticized the Soviet Union's interpretation of Marxism–Leninism, in particular Khrushchev's support for peaceful coexistence and its interpretation. This led to increasingly hostile relations, and eventually the Sino-Soviet split. From here, Chinese communists played a decreasing role in helping their former allies because the Viet Minh did not support China against the Soviets.
Following worsening relations between the Soviet Union and China as a result of the Sino-Soviet split of 1956–1966, as many as 1.5 million Chinese troops were stationed along the Sino-Soviet border in preparation for a full-scale war against the Soviets.
Vietnam joined the Council for Mutual Economic Assistance (CMEA) on June 28, 1978. Soviet military aid to Vietnam increased from $75-$125 million in 1977 to $600-$800 million in 1978.
On November 3, 1978, Vietnam and the Soviet Union signed a formal military alliance. The Soviet Union supported Vietnam's invasion of Cambodia, launched in December 1978.
Following the death of Mao in September 1976, the overthrow of the Gang of Four and the ascent of Deng Xiaoping, the Chinese leadership started the reform and opening up to transition to a market economy, denounced the Cultural Revolution, and collaborated with the US against the Soviet Union.
As France withdrew from a provisionally divided Vietnam in late 1954, the United States increasingly stepped in to support the South Vietnamese leaders due to the Domino theory, which theorized that if one nation would turn to communism, the surrounding nations were likely to fall like dominoes and become communist as well. The Soviet Union and North Vietnam became important allies together due to the fact that if South Vietnam was successfully taken over by North Vietnam, then communism in East Asia would find its strategic position bolstered. In the eyes of the PR China, the growing Soviet-Vietnamese relationship was a disturbing development; they feared an encirclement by the less-than-hospitable Soviet sphere of influence.
The United States and the Soviet Union could not agree on a plan for a proposed 1956 election meant to unify the partitioned Vietnam. Instead, the South held a separate election that was widely considered fraudulent, leading to continued internal conflict with communist factions led by the Viet Cong that intensified through the late 1950s. With supplies and support from the Soviet Union, North Vietnamese forces became directly involved in the ongoing guerrilla war by 1959 and openly invaded the South in 1964.
The United States played an ever-increasing role in supporting South Vietnam through the period. The U.S. had supported French forces in the First Indochina War, sent supplies and military advisers to South Vietnam throughout the 1950s and early 1960s, and eventually took over most of the fighting against both North Vietnam and the Viet Cong by the mid-1960s. By 1968, over 500,000 American troops were involved in the Vietnam War. On 20 January 1969, Richard Nixon became US President.
Due to a lack of clear military success and facing increasingly strident opposition to the war in the U.S., American forces began a slow withdrawal in 1969 while attempting to bolster South Vietnam's military so that they could take over the fighting. In accordance with the Paris Peace Accords by 29 March 1973 all U.S. combat forces had left South Vietnam, however North Vietnamese combat forces were allowed to remain in place. North Vietnam attacked South Vietnam in early 1975 and South Vietnam fell on 30 April 1975.