In keeping with recent attention to the global dimensions of the First World War, this essay explores how Isaac Rosenberg, Thomas Hardy, Robert Service, Wilfred Owen, Mary Borden and other wartime poets seized on and developed the cosmopolitan potentialities of poetry, in the sense of grounded attachments that span specific cultural and national differences. While the anti-heroism of First World War poetry has been amply discussed, its overlapping but distinct capacity for imaginative solidarity across enemy lines, if often acknowledged, remains less fully explored. Drawing on the theoretical work of Paul Gilroy, Richard Rorty, Martha Nussbaum and Sigmund Freud, but above all attending to the poetry, this chapter examines First World War poems that not only state but linguistically, formally, and thematically enact what Rosenberg called ‘cosmopolitan sympathies’ with the enemy other.