Would America dare to bring down a Chinese bank?

If any politician has the demeanour to ease tensions with Beijing, it is Janet Yellen. America’s treasury secretary comes across as a twinkly eyed professor, rather than a foreign-policy hawk. Sure enough, she used a recent trip to China, which ended on April 9th, to praise the “stronger footing” that Sino-American relations are now on compared with a year ago. Ms Yellen was not merely there to extend an olive branch, however. She also carried a warning for China’s banks: those that help “channel military or dual-use goods to Russia’s defence-industrial base expose themselves to the risk of US sanctions”.

Ms Yellen’s warning marks the latest escalation in America’s financial war with Russia. Since Vladimir Putin’s invasion of Ukraine in February 2022, lawmakers in Washington have issued sanctions on nearly 3,600 Russian targets, according to Castellum.AI, a compliance firm. Allies, especially in Europe, have issued many more. Central-bank reserves have been frozen and exports of military goods banned. SWIFT, a messaging service used by 11,500 banks to make around $35trn-worth of cross-border payments a day, has banned some of Russia’s biggest banks. Yet none of this has stopped Russia from outproducing the West in artillery shells, holding its frontline and gearing up for a big push.