“Artillery fire lights up the sky and breaks my heart. I hope my compatriots in Ukraine are taking care of themselves and their families,” said a user on Weibo, often called China’s Twitter, on February 27. The message was quickly blocked, according to Free Weibo , a service of Great Fire, which tracks Chinese censorship online. Two days later, a very different message appeared on Weibo : “I support fighting! According to Free Weibo, Taiwan and America have gone too far.” The messages–and their quick disappearance–show how Chinese social media platforms find themselves in the crosshairs of the Russia- Ukraine...