What motivates states’ choice of social classification? Existing explanations highlight scientific beliefs of modern states or social engineering by ideological regimes. Focusing on the initial state-building period of two Communist regimes, China and North Korea, this article complements the existing literature and suggests that social classification reflects three missions of political leaders: regime distinction, governance, and power consolidation. Population categories are created to distinguish the new government from the old, to selectively provide welfare, and to attack political opponents. The varying weight of the missions and their manifestation in social classification depend on new ruling elites’ cohesion and past experiences. This comparative historical analysis sheds light on the rise of political chaos in China and the personalistic dictatorship in North Korea in the 1970s.