Xi Jinping has called Vladimir Putin his best friend. But now the Russian leader is in urgent need of help from China. Putin’s army is bogged down in Ukraine and running short of ammunition. Should Xi prove that he is a friend indeed by supplying Russia with weapons? China’s decision will say a lot about how it sees the future of the world. A choice to supply Russia with weapons would suggest that China believes that intensified rivalry with the US is unavoidable — and perhaps desirable. By contrast, a decision not to give Russia weapons would indicate that China still believes that tensions with the US are manageable and that globalisation can be saved. Influential voices in Beijing fully understand the risks of supplying Russia with the crucial munitions that Moscow’s forces are running short of — such as artillery shells and drones. In the Financial Times last week, Zhou Bo, a former colonel in the People’s Liberation Army, wrote: “If Beijing takes Moscow’s side in the conflict, then we are already in the dawn of the third world war.” Put like that, a Chinese decision to supply Russia with weapons sounds inconceivable. And yet the US government believes that there is a serious debate under way in Beijing — and that China may ultimately make this fateful decision. The reason that Xi might decide to dramatically increase support for Putin goes back to the “no limits” partnership announced by the Russian and Chinese leaders in February 2022 — three weeks before Russia launched its full-scale invasion of Ukraine. More important than the announcement of the partnership was the shared analysis that underpinned it. Putin and Xi laid out a common understanding of the world. They both see the US as the central threat to their countries’ ambitions and political regimes. Fighting back against American power is the common task that unites them. Xi has visited Putin more than he has visited any other world leader. The worst-case scenario for him would be the fall of Putin and his replacement with a pro-western leader. That still feels like a remote possibility. But, even if Putin remains in power, a humiliated and weakened Russia would make the US look resurgent and China more isolated. Some in Beijing argue that once Russia had been dealt with, America would turn on China.