Chapter 7 offers a newly comprehensive interpretation of the political and ideological war that escalated at the heart of the First World War. It argues that at the core the war turned into a transatlantic struggle not only between war-aim agendas but indeed between competing liberal-progressive, imperialist and Bolshevik visions of peace and future order. It elucidates the unprecedented scope of this struggle by examining not only the aims and conceptions of the different wartime governments and leaders like Wilson, Lloyd George, Ludendorff and Lenin but also the contributions that intellectuals, opinion-makers and other non-governmental actors and associations on both sides of the trenches made to what became the greatest war for “national minds” and “world opinion” in history (up until then). And it brings out the far-reaching consequences this struggle had, both for peacemaking after the war and in the longer term. The analysis emphasises that it catalysed or brought to the fore formative ideas and ideologies of international and domestic-political order for the remainder of the “long” 20th century, including notions of self-determination and universal but hierarchical democratisation, ideas for a modern league of nations and competing blueprints for an internationalist system of communist states.