This chapter examines the social conditions in which armed bands emerged in autumn 1943, and communists’ efforts to build their leadership therein. Exploring the differences between the slum proletariat in Rome’s peripheral borgate and the industrial working class of the North, it explains how their respective forms of mobilisation related to communists’ differing conceptions of ‘class struggle’. This focus on the particular forms of social revolt on Rome’s periphery allows us to explain the relative strength of the dissident communists in these areas compared to all other Resistance forces.