Why did Western European states agree to the enlargement of the EU and NATO? Frank Schimmelfennig analyzes the history of the enlargement process and develops a theoretical approach of ‘rhetorical action’ to explain why it occurred. While rationalist theory explains the willingness of East European states to join the NATO and EU, it does not explain why member states decided to admit them. Using original data, Schimmelfennig shows that expansion to the East can be understood in terms of liberal democratic community building. Drawing on the works of Jon Elster and Erving Goffman, he demonstrates that the decision to expand was the result of rhetorical action. Candidates and their supporters used arguments based on collective identity, norms and values of the Western community to shame opponents into acquiescing to enlargement. This landmark book makes an enormous contribution to theory in international relations and to the study of European politics.