This article examines and further develops the relationship between the theory of uneven and combined development (UCD), recently taken up by International Relations (IR) scholars to furnish a social theory of ‘the international’, and the Gramscian concept of ‘passive revolution’, which refers to a molecular process of top-down revolution and state formation that preserves ruling-class power by transforming its social base. To this end, the paper: (1) advances a productive distinction between ‘societal’ and ‘(geo)political’ multiplicity, increasing the transdisciplinary potential of UCD and challenging dominant state-centric approaches to IR; (2) demonstrates that UCD is central to creating the conditions for passive revolution; and, (3) argues that UCD illuminates the distinct spatial dimensions of passive revolution, for which the succession of ‘classes’ in time requires the expansion of capitalist social relations in space. To illustrate these claims, the article demonstrates how the American Civil War is best understood as an inter-societal conflict, exacerbated by the coexistence of two social formations within a single state, leading to war. It then shows how, upon victory, the North’s abolition of enslaved labour and the subsequent attempt to re-subsume the South within a single sovereign polity constituted a radical instance of passive revolution.