It seemed that China’s censors had finally muzzled Yang Jisheng, the famed chronicler of the Mao era. Last year, he had finished writing a widely anticipated history of the Cultural Revolution. But officials warned him against publishing it and barred him from traveling to the United States, he has said, and he stayed muted through the 50th anniversary of the start of that bloody upheaval.

Now Mr. Yang has broken that silence with the publication of his history of the Cultural Revolution, “The World Turned Upside Down,” a sequel to “Tombstone,” his landmark study of the famine spawned by Mao’s policies in the late 1950s. The 1,151-page book is the latest shot fired in China’s war over remembering, or forgetting, the dark side of its Communist past, a struggle that has widened under the hard-line president, Xi Jinping.

“I wrote this book to expose lies and restore the truth,” Mr. Yang writes in the book, which has been quietly published in Hong Kong, beyond the direct reach of Chinese censors. “This is an area that is extremely complicated and risky, but as soon as I entered it, I was filled with passion.”

Since Mr. Xi took power in 2012, the Communist Party authorities have denounced historians who question the party’s lionization of its past and exhume grim events like the Cultural Revolution, which Mao started in 1966, opening a decade of purges and bloodshed.

Tens of millions were persecuted and perhaps a million or more people were killed in that convulsive time. But officials say dwelling on such events is subversive “historical nihilism” aimed at corroding the party’s authority.

In a sign of how Chinese politics has chilled, Mr. Yang has said little publicly about the book. ...