This dissertation examines the role of the United States in the mass expulsion of Germans from East-Central Europe from spring 1945 through 1947. By agreeing to allow Czechoslovakia and Poland to expel their German minority populations in 1943, and again in 1945 under Article XIII of the Potsdam Agreement, the United States permitted approximately 14 million to 16 million Germans to be forcibly relocated into a truncated, war-torn Germany, an incident that is the largest example of ethnic cleansing in world history. Although these expulsions threatened the postwar stability of Europe and were of great concern they were of marginal interest to most people in the United States. Informed discussion of these expulsions occurred among a fairly narrow group of military officials, diplomats, politicians, intellectuals, and immigrants or exiles. In fact there was a dearth of contemporary debate and analysis on all aspects of the United States role in the expulsion of Germans, both within government and in society more generally. Newspaper reports, magazine articles, diplomatic documents, government documents and the personal papers of diplomats and politicians reveal that the expulsion of Germans was a secondary issue to the United States government. Despite considerable media coverage, it seems that most Americans lacked both awareness of and compassion for the plight of the German expellees. These expulsions however, changed the politics and the demographics of Europe forever and made the ethnic cleansing of the minority populations of nations an international legal precedent. Today, the expulsions remain a controversial subject within the region of East-Central Europe where the people of Czechoslovakia, Germany and Poland still debate the expulsions as if they occurred yesterday. In the United States, however, the expulsions have been long forgotten. This dissertation is unique in that examines the involvement of the United States in the planning of the expulsions and the reaction of the American press, intellectuals and policymakers whereas previous literature has focused very sparingly on this aspect of the expulsions.