Historians have often considered the international veterans’ organizations which came into being after World War I as proof of the pacifist, internationalist orientation of the majority of the Great War ex-combatants. However, veterans active in these organizations were often inspired by specifically national and partisan objectives that belie any simplistic equation between altruistic transnational activism, international cooperation and pacifism. Conceiving of war veterans as transnational actors, this article explores the origins and decline of the veterans’transnational sphere in the interwar period. It singles out four shades of competing veterans’ internationalism and describes the crucial differences that separated actors such as Henri Barbusse, René Cassin, Henri Pichot and Carlo Delcroix, among others. The article argues that both the veterans’ organizations and their protagonists, while reaching out across national borders, remained embedded in specific constellations of personal trajectories, political partisanship, nation-state interests and inter-state alliances. Their political and social activities also tried to reshape, and were subjected to, existing or emerging spatial configurations such as Great Power alliances and wider internationalist projects. Thus, the article shows that there was no homogeneous transnational sphere in international veteran politics; it was rather the competition between different internationalist practices and projects which shaped veterans’ transnational activities.