Scholars seeking to decode the organizing logic of the mass violence that marked China’s Cultural Revolution of the 1960s have long followed the clue provided by the Mao-era slogan “If the father is a hero, the son is a good fellow; if the father is a reactionary, the son is a rotten egg.” They have argued that when the Chinese leader Mao Zedong put out the call to “bombard the headquarters,” people whose families had been labeled “bad elements” rose up to overthrow members of the privileged official class, who then retaliated, giving rise to rounds of conflict based on class status. Walder, however, has devoted decades to examining the local records of nearly all of China’s 2,000-plus county-level jurisdictions. He found that factions emerged from the splintering, rather than the congealing, of class-based groups. Small clusters of students, workers, and cadres struggling to respond to Mao’s shifting directives made split-second decisions about whom to align with. Political identities did not shape the conflict; they emerged from it. To explain this process of identity formation, he offers a theory of “factions as emergent properties” and suggests that similar dynamics may characterize social movements everywhere.