This article argues that warfare has been marginalised in theories of nationalism, but that in conjunction with nationalism is vital for understanding the rise of nation-states, the formation of nations and the nature of the international system. It offers a critique of statist approaches, suggests mechanisms through which warfare may sacralise nations, and explores different patterns of nation-state formation as they affect the interstate system. In particular, it emphasises tensions between state- and nation-formation as activated by the fortunes of war and the destabilising effects of waves of imperial dissolution, which are accompanied by patterns of re-imperialization. It suggests that it is simplistic both to claim that war has led to...