The civilizing mission associated with nineteenth-century colonialism became harder to justify after the First World War. In an increasingly anti-imperialist culture, elites reformulated schemes for the “improvement” of “inferior” societies. Nation building, social engineering, humanitarianism, modernization or the spread of democracy were used to justify outside interventions and the top-down transformation of non-western, international or even domestic societies. The contributions in Civilizing Missions in the Twentieth Century discuss how these justifications influenced Polish nation building, Scandinavian disarmament proposals and technocratic social policies in the interwar years. Treatment of the second half of the century covers the changing cultural context of European humanitarianism, as well as the influence of American social science on US foreign policy, more particularly democracy promotion. Contributors are: Boris Barth, Rolf Hobson, Jürgen Osterhammel, Frank Ninkovich, Bianka Pietrow-Ennker, Karen Gram-Skjoldager, Esther Moeller, and Jost Dülffer.