In the years between 1974 and 1988, the Front for the Liberation of Mozambique (FRELIMO), the ruling party of independent Mozambique sought to "mentally decolonize", "purify", and "reeducate" urban citizens deemed to be morally impure and an obstacle to the socialist revolution. FRELIMO violently uprooted thousands of people from the cities and sent them to reeducation and labor camps in the countryside. This exercise in social engineering, which resembled the Great Terror in Stalin's USSR and the Cultural Revolution in China, was carried out by ordinary urban citizens who denounced, hunted down, and helped to expel their fellow compatriots. My dissertation examines the historical, ideological, and socio-political dynamics that drove Mozambicans out of the cities, and documents victims' experiences of reeducation and forced labor. My study moves beyond explanations about why the regime pursued such objectives. It explores the ways in which ordinary urban citizens recast the regime's socialist principles and transformed them into an arena of debate over moral citizenship. Based on extensive archival and ethnographic research, this study redeems a silenced chapter of Mozambique's recent history. It contributes to the understanding of why "ordinary" people participate in violent schemes of social engineering against their compatriots in autocratic regimes.