Peasant revolutions in the twentieth century played a major role in shaping the course of world history. Peasants, identi¢ed by Marx as a species facing extinction in the face of rapid industrialization, in fact became one of the primary forces of social change in this century. This research re£ects the recent trends in scholarship on revolutions. Through the comparative-historical method, it seeks to explain very di¡erent patterns of peasant revolutionary behavior in two revolutions in South China between 1926 and 1934. In the case of Hunan, peasants staged a radical revolution without signi¢cant outside mobilization. In the case of Jiangxi, peasants remained politically passive even under very intense mobilization from Mao Tse-tung's Red Army. Following the recent movement away from materialistic and instrumentalist perspectives, which tend to emphasize factors such as economic systems, class relations, and rational choice, this research argues that the cause of di¡erent revolutionary patterns in Hunan and Jiangxilies in the legitimacy of organizational structures of rural communities. Agrarian revolutions could happen when peasants attempt to overthrow the illegitimate communal organizational frameworks.