The introductory chapter explains the significance of the phenomenon of mass expulsion. It has affected over 30 million people in the last 120 years (1900–2020) and persists in our current moment, with 1.56 expulsions per year over the last 50 years. The chapter examines the shared discourse among democratic and authoritarian leaders that frame mass expulsion as an “orderly and humane” policy. The advocacy for this atrocity by governments, media, and public intellectuals makes it unique among related phenomena. The chapter details the central research questions—why and how governments expel groups en masse—and summarizes the main arguments. It explains the research design, justifies the case selection, and briefly introduces the positive and negative case studies. The chapter concludes with an outline of the chapter structure of the book.