On 17 February 1979, approximately 200,000 Chinese troops crossed the border into northern Vietnam in simultaneous assaults along several corridors, beginning a war that would last until 16 March. The Sino-Vietnamese War killed an estimated 20,000 to 50,000 Chinese soldiers and 10,000 to 30,000 Vietnamese soldiers, plus unknown numbers of Vietnamese civilians; China withdrew by mid-March having achieved none of its stated objectives — the conflict was the largest military engagement between two communist states during the Cold War.
The war was a direct consequence of the Sino-Soviet split. By 1978, the two communist great powers had armed clients in Indochina on opposite sides of a civil war. The Soviet Union had given substantial military aid to Vietnam. The People’s Republic of China had given substantial military aid to the Khmer Rouge in Cambodia. When Vietnam invaded Cambodia in December 1978 and installed a Vietnamese-backed government in Phnom Penh, the Chinese position in the region was effectively overturned.
The context
Vietnam’s invasion of Cambodia on December 25, 1978, was the immediate cause. The Vietnamese army, more than 100,000 strong, attacked the Democratic Kampuchea regime of Pol Pot and within two weeks had captured Phnom Penh (January 7, 1979). The new government, the People’s Republic of Kampuchea, was led by Heng Samrin and Hun Sen, both former Khmer Rouge officials who had defected to the Vietnamese. The invasion ended the genocide of the Cambodian people — between 1.5 and 2 million Cambodians had been killed by the Khmer Rouge between 1975 and 1978 — but it also gave Vietnam control over a country that China had considered its own client.
The broader context was the Sino-Soviet rivalry. Vietnam had signed a Treaty of Friendship and Cooperation with the Soviet Union in November 1978, committing the Soviet Union to military assistance in the event of an attack. The treaty was the culmination of a gradual Vietnamese drift toward Moscow, and it was the final breach with Beijing. The Chinese government, which had been providing economic and military aid to Vietnam throughout the 1960s and early 1970s, viewed the treaty as a betrayal.
The Chinese response to the Cambodian invasion was a sharp public warning. Deng Xiaoping, who had consolidated power at the third plenum of the 11th Central Committee in December 1978, told a visiting American delegation in late January 1979 that “we have to teach Vietnam a lesson.” The statement was made to the U.S. delegation led by David Aaron; the Americans were not informed of the specific plan, but Deng’s meaning was clear.
The attack
The Chinese attack began on February 17, 1979, with simultaneous assaults across the Sino-Vietnamese border at several points. The Chinese forces included units from the Guangzhou and Kunming military regions, total force was approximately 200,000 troops, organized into infantry divisions, artillery, and supporting armor. The Vietnamese defenders were spread more thinly but were well-prepared: the Vietnamese general staff had been warning of a Chinese attack since the Cambodian invasion, and the People’s Army of Vietnam had reinforced the northern border with experienced units.
The Chinese advance was slow and costly. The Vietnamese had fortified the border in depth, and the country has few roads into the interior from the Chinese side. The Chinese had to advance along narrow corridors, and they suffered heavily from Vietnamese mines, ambushes, and counterattacks. The Chinese captured the northern provincial capital of Cao Bang on February 25 and Lao Cai on March 4, but they did not threaten Hanoi itself. By the time the Chinese government announced a withdrawal on March 5, the Chinese forces had advanced no more than 50 to 80 kilometers into Vietnamese territory at any point.
The Chinese withdrawal began on March 6 and was completed by March 16. The withdrawal was orderly, but the Chinese forces destroyed what they could not carry out, including villages, infrastructure, and the agricultural infrastructure of the border regions. The destruction was deliberate; the Chinese explicitly stated that they wanted to demonstrate to Hanoi the cost of supporting the Soviet Union at the expense of China.
The consequences
The war was a military embarrassment for China. The Chinese had expected a quick operation that would force Vietnam to withdraw from Cambodia; instead, the Chinese forces suffered heavy casualties and were forced to withdraw after a month. The Vietnamese, despite being outnumbered, inflicted significantly higher casualty ratios than the Chinese had anticipated. The war demonstrated that the Chinese military, which had not fought a major conventional war since the Sino-Indian War of 1962, was poorly prepared for a modern combined-arms operation.
The war also demonstrated the limits of the Sino-Soviet split. The Soviet Union provided intelligence and material support to Vietnam during the war, but it did not intervene directly. Soviet ships were dispatched to the South China Sea in a show of support, and Soviet transport aircraft flew supplies to Vietnam, but the Soviet Union did not want a direct confrontation with China. The Chinese correctly calculated that the Soviet response would be limited, but they paid a higher price than expected to test that calculation.
The war was followed by a decade of continued Sino-Vietnamese tension, including border clashes in 1981, 1984, 1986, 1987, and 1988, the last of which produced the naval battle of Johnson South Reef in the Spratly Islands. The Sino-Vietnamese relationship did not normalize until 1990, when the Cold War was ending and Vietnam withdrew from Cambodia.
Deng’s calculation
Deng Xiaoping’s decision to launch the war is sometimes read as a personal power play; the 1979 attack consolidated his position within the Chinese Communist Party after the Maoist excesses of the Cultural Revolution. The decision was also, however, an exercise in strategic signaling. The message was for three audiences: Vietnam, the Soviet Union, and the United States.
The message to Vietnam was that alignment with Moscow would have a cost. The message to Moscow was that China would not be contained, even if it meant a direct military confrontation with a Soviet ally. The message to Washington was that China was a serious strategic partner in the anti-Soviet alignment that had been constructed in 1972. The visit of Deng Xiaoping to Washington in January 1979, the same month as the Cambodian invasion, was the diplomatic counterpart to the military operation.
The war achieved some of its signaling goals. It did not, however, achieve the operational objective: Vietnam remained in Cambodia until 1989, the Khmer Rouge continued to fight a guerrilla war with Chinese and Thai support, and the Sino-Vietnamese border remained tense for another decade. The 1979 war was a strategic miscalculation, executed with limited means, that cost thousands of Chinese lives to demonstrate a point that the diplomatic record already made clear.
For the diplomatic framework that made the war possible, see the Sino-Soviet split overview. For the Soviet parallel, see the Soviet-Afghan War overview.