To conclude this volume, we first highlight some of the variations between the cases that have been covered before situating them in the historical evolution of the international system. We show that, contrary to what has been argued by some critiques, “political Marxism” does not adopt an “internalist” perspective on the transitions to capitalism. “National” or regional transitions are always co-constituted phenomenon. We explain how, historically, the spread of capitalism was conveyed by the international state system and fuelled, first, by geopolitical competition, and, second, by the emergence of capitalist imperialism. We conclude by setting an agenda for further research to fill some of the gaps that remain in our research project.