The troops gathered on the border. The supreme leader decided that it was time to invade, to teach the other side a lesson. Shortly afterwards, troops breached the internationally recognised border and clashed with local forces. Not Ukraine 2022, but Vietnam 1979. In January of that year, the Chinese leader Deng Xiaoping told the US president Jimmy Carter that he wanted to “spank the butt” of his neighbours. For a month, Chinese and Vietnamese forces clashed, leading to a death toll of tens of thousands. Chinese troops withdrew in March 1979, when, unlike Vladimir Putin, Deng sensibly decided to declare a famous victory and head home. Since then, there has been no unambiguous breach of an international border by Chinese troops. China’s brief invasion of Vietnam isn’t much talked about today during the Ukraine crisis. None of the western actors wants to bring it up when they are trying to pressure China over its general fixation on the sanctity of national sovereignty. And Moscow won’t mention it, because it brings back an awkward memory for their friends in Beijing: China’s 1979 venture wasn’t really about Vietnam, but about Russia. Sino-Soviet relations had become poisonous ever since the split between the two communist superpowers in 1960. Vietnam, with Soviet backing, invaded and occupied Cambodia in 1978, ousting the Khmer Rouge. In the bizarre cold war politics of the time, both the US and China supported Pol Pot’s genocidal regime because its Vietnamese enemy was supported by Moscow. On 4 February, at the Beijing Winter Olympics, Xi Jinping and Putin declared a “friendship without limits”. Shortly afterwards, Russia invaded Ukraine; most analysts judge that Beijing had some idea that Russia would attempt to seize further Ukrainian territory but almost certainly did not realise that there would be a full invasion. China is genuinely concerned about the Russian destruction of Ukraine’s sovereignty, although it will not say so in public, calling instead at the UN for vaguely defined humanitarian gestures and censoring pro-Ukraine sentiments on Chinese social media. But Beijing seems to see little benefit in becoming a mediator in the conflict, judging that many of its partners in the global south, such as Pakistan and South Africa, do not consider a European crisis to be an existential test for them or for China. China’s primary motivations in seeking peace between Russia and Ukraine are pragmatic. Ukraine is an important, though not crucial, source of grain for China and having to find new suppliers of cheap cereals in a hurry for its middle-class population could fuel inflation. There are pluses for China in a settlement that leaves Putin in charge but weaker and still sanctioned. China could become the sole major market for Russia’s wheat and fossil fuels, obtainable at bargain prices, although traditional allies of Russia such as India have not taken nearly such a hard line against Moscow as the west and might also provide markets. Russia is also still China’s preferred partner to create semi-formal military groupings (rather than Nato-style binding alliances) against the west. Beijing has repeatedly suggested the Shanghai Cooperation Organization should be used to mediate in Ukraine; the SCO is a would-be Nato dominated by China and Russia, with India and central Asian states as members. However, the Russia-China relationship is not just about power politics pure and simple. Somewhere in the pragmatic relationship of the present day lies muscle memory of a more emotional link between China and Russia, not just the Soviet Union but a longer tradition of Russian literature and culture that shaped the modern Chinese revolution. One of China’s greatest modern authors, Ba Jin, took his pen name from syllables in the Chinese transliterated names of the revolutionaries Bakunin and Kropotkin. Young Chinese women, leaving their families to take part in the communist uprising of the 1940s, would cite Turgenev’s poem Threshold (1878). The work is written in the voice of a man speaking to a young woman about to join the anti-tsarist movement; he says she will suffer “alienation” and “loneliness”, to which she replies: “I know, and I still want to enter.” The heyday of that Russian influence was in the 1940s, when Soviet ideology and the lure of Soviet technology also influenced Chinese visions of Moscow as the future, and in the 1950s, when the country was isolated from the US. It was emotionally distinct from the anti-foreign Cultural Revolution that Xi grew up with, but it was very much the world of his father, the veteran revolutionary general Xi Zhongxun. From the 1960s to the end of the cold war, the love turned to hatred, as ideological disputes brought the two countries close to war over border islands on the Ussuri River in 1969, prompting Chinese enthusiasm for the opening to the US that took place just over 50 years ago. In recent decades, the relationship has become warmer, as Moscow and Beijing realise that it gives them both cover against the encroachment of the west. Yet the post-cold war trajectory of Putin’s Russia and Xi’s China is not the same. China has seen its economy and global influence soar, while Russia’s spending power and life expectancy have shrunk. In some areas, such as central Asia, cooperation masks mutual distrust. Russian residents of Siberia have become increasingly resentful of Chinese investment in their region. China has created one of the most powerful civilian and military economies in the world, yet Russia’s elites still look to the west, many considering China rich but “uncultured” (nekulturny, a much stronger insult in Russian than English). China feels a little superior because Russia has never come up with a Huawei; Russia is a touch contemptuous because China has never produced a Dostoyevsky. In that ambivalence, along with unmentioned episodes such as the 1979 proxy war between them, lies a shared history of respect and resentment. This still seems to flavour the relationship today between Xi and Putin. Rana Mitter is author of China’s Good War: How World War II Is Shaping a New Nationalism (2020). He teaches at Oxford University