In 1968 Vietnam invaded Cambodia to oust the murderous Kmer Rouge government. The Chinese, who backed the Kmer Rouge, were incensed. There were disputes that arose between both regional powers before the Vietnamese War and now that the Americans were gone, they could go ahead and return to their original political modality of mutual anomie. China was Cambodia’s ally, and China took umbrage at the invasion by the Vietnamese army. One might think that the Chinese Army was a behemoth versus Vietnam. But their armies were more pari passu than mismatched. In fact the Vietnamese were more ready to fight and had the instincts to go against larger forces. The Chinese were surprised by the efficient army the Vietnamese had become in the preceding decades fighting America.
This is an odd fact and few in the west know that China and Russia were sworn brothers in the fight to support North Vietnam’s Communist government. By the time the US was out of Vietnam, the Soviet Union and China were both interpreting Communism a bit differently. As it turns out Communist ideology is polysemous.
China invaded Vietnam along multiple routes on February 17th 1969 and left on March 16th 1979. Part of the problem was that the Chinese felt the Soviets had betrayed them or at least betrayed the primacy of Communism. China wanted the Soviets to back their efforts to force the Americans out of the region. The Soviets were broke and fatigued by the surfeit of warfare and spending, and so decided to a détente. A bit too laissez faire for the Chinese. The thawing relations with the Soviets and the also stuck in the craw of Den Xiaoping. In fact in 1962, when the Soviets blinked at the Cuban Missile Crisis, the Chinese were disappointed.
Then the Soviets sold missile technology to China’s sworn enemy: India.
Russia had also given Cambodia 400 tanks, hundreds of anti-tank missiles and surface-to-air missiles. Some 8,000 Russian “advisers,” and intelligence officers aided the Cambodians including signal intelligence and spying.
In about three weeks of fighting, Chinese units inflicted considerable casualties on the Vietnamese but never could draw them out in a set piece battle. After 70,000 casualties, Deng Xiao Peng declared the war over and China the Winner. The Vietnamese and the Soviets and Laotians were all happy to quell the ambitions of a newly triumphant Communist presence: an expansionist China. Vietnam lost about 120,000 people and the Chinese lost about 25,000. At the end of the day, The Chinese were not able to scare Vietnam out of Cambodia. In reality Chinese troops were not up to snuff, using old equipment and old tactics, it was a wake up call for them all.