After the First World War, Britain's economy and security depended on imperial cooperation for reconstruction. Yet, the war and the culture based on the League of Nations and its principles of self-determination and internationalism challenged efforts to strengthen imperial unity. Imperialists had to re-envision a more inclusive idea of empire in the midst of nationalist uprisings abroad and labor unrest at home. By analyzing circulated propaganda and speeches about the League, this thesis traces the efforts of British political thinkers who used the League's principles to manage the domestic discontent that threatened unity. It demonstrates how they tried to relate the League's principles to the ordinary Britisher's historical commitment to internationalism and imperial humanitarianism. Invoking social psychology, imperialists tapped into a universal interest in the League to re-legitimize the British Empire and establish a more enduring psychological imperial unity between the metropole and the empire after the war.