Debates over ‘modernity’ have been central to the development of historical-sociological approaches to International Relations (IR). Within the bourgeoning subfield of International Historical Sociology (IHS), much work has been done to formulate a historically dynamic conception of international relations, which is then used to undermine unilinear conceptions of global modernity. Nevertheless, this article argues that IHS has not proceeded far enough in successfully remedying the problem of unilinearism. The problem remains that historical narratives, informed by IHS, tend to transhistoricise capitalism, which, in turn, obscures the generative nature of international relations, as well as the fundamental heterogeneity of diverging paths to modernity both within and beyond western Europe. Based on the theory of Uneven and Combined Development, Political Marxism, and Robbie Shilliam’s discussion of ‘Jacobinism’, this article first reinterprets the radical multilinearity of modernity within western Europe, and then utilises this reinterpretation to provide a new reading of the Ottoman path to modernity (1839–1918). Such a historical critique and reconstruction will highlight the significance of Jacobinism for a more accurate theorisation of the origin and development of the modern international order, hence contributing to a deeper understanding of the international relations of modernity.