The Chinese Cultural Revolution was a bitter thing, a catastrophe comparable in its societal effects, and similar in its historical feel, to the terrors of Stalin and the French Revolution. No one knows how many died; historians say up to two million. But what I find myself thinking of these days is the ritual humiliations, the “struggle sessions.”

In the mid-1960s Mao Zedong, suspicious of those around him, wary of the moves of erstwhile Soviet allies, damaged by a disastrous famine his policies had caused, surveyed the scene and decided it was time for a little mayhem. The problem wasn’t his disastrous ideology, it was, he wrote, “feudal forces full of hatred towards socialism . . . stirring up trouble, sabotaging socialist productive forces.” The party had been “infiltrated” by pragmatists and revisionists. He wrote—it is the epigraph of Frank Dikötter’s “The Cultural Revolution: A People’s History, 1962-1976”—“Who are our friends? Who are our enemies? That is the main question of the revolution.”