The Killing Wind: A Chinese County’s Descent into Madness During the Cultural Revolution by Tan Hecheng, translated from the Chinese by Stacy Mosher and Guo Jian Oxford University Press, 505 pp., $34.95

The Xiao River rushes deep and clear out of the mountains of southern China into a narrow plain of paddies and villages. At first little more than an angry stream, it begins to meander and grow as the basin’s sixty-three other creeks and brooks flow into it. By the time it reenters the mountains fifty miles to the north, it is big and powerful enough to carry barges and ferries.

Fifty years ago, these currents transported another cargo: bloated corpses. For several weeks in August and September 1967, more than nine thousand people were murdered in this region. The epicenter of the killings was Dao County (Daoxian), which the Xiao River bisects on its way north. About half the victims were killed in this district of four hundred thousand people, some clubbed to death and thrown into limestone pits, others tossed into cellars full of sweet potatoes where they suffocated. Many were tied together in bundles around a charge of quarry explosives. These victims were called “homemade airplanes” because their body parts flew over the fields. But most victims were simply bludgeoned to death with agricultural tools—hoes, carrying poles, and rakes—and then tossed into the waterways that flow into the Xiao.

In the county seat of Daozhou, observers on the shoreline counted one hundred corpses flowing past per hour. Children danced along the banks competing to find the most bodies. Some were bound together with wire strung through their collarbones, their swollen carcasses swirling in daisy chains downstream, their eyes and lips already eaten away by fish. Eventually the cadavers’ progress was halted by the Shuangpai dam where they clogged the hydropower generators. It took half a year to clear the turbines and two years before locals would eat fish again.

For decades, these murders have been a little-known event in China. When mentioned at all, they tended to be explained away as individual actions that spun out of control during the heat of the Cultural Revolution—the decade-long campaign launched by Mao Zedong in 1966 to destroy enemies and achieve a utopia. Dao County was portrayed as remote, backward, and poor. The presence of the non-Chinese Yao minority there was also sometimes mentioned as a racist way of explaining what happened: those minorities, some Han Chinese say, are only half civilized anyway, and who knows what they might do when the authorities aren’t looking?

All of these…