SHANGHAI — Yang Jisheng knows all about censorship. His book “Tombstone,” an epic account of Mao Zedong’s great famine, is banned in China.

His former employer, Xinhua News Agency, refused to let him go to the U.S. to pick up an award at Harvard last week. That didn’t stop the retired journalist from writing a speech, which triumphantly noted that pirated editions of Tombstone circulate even in the remotest parts of China, despite the efforts of censors.

He said he knows this because readers send him fervent letters of support, what he termed testament to “the power of truth to break through the bronze walls and iron ramparts constructed by the government.”

It was a message of defiance: Despite a monumental edifice of controls, censorship is losing.

Lately, President Xi Jinping’s administration has run into mounting resistance to its efforts to tighten its vise even more completely over the country’s printed works, its airwaves and digital networks, while it strengthens the Great Firewall to keep out foreign content.