Why are forced displacement, ethnic cleansing and genocide an enduring feature of state systems? In this ground-breaking book, Heather Rae locates these practices of 'pathological homogenisation' in the processes of state building. Political elites have repeatedly used cultural resources to redefine bounded political communities as exclusive moral communities, from which outsiders must be expelled. Showing that these practices predate the age of nationalism, Rae examines cases from both pre-nationalist and nationalist eras: the expulsion of the Jews from fifteenth century Spain, the persecution of the Huguenots under Louis XIV, and in the twentieth century, the Armenian genocide, and ethnic cleansing in former Yugoslavia. She argues that those atrocities prompted the development of international norms of legitimate state behaviour that increasingly define sovereignty as conditional. Rae concludes by examining two 'threshold' cases - the Czech Republic and Macedonia - to identify the factors that may inhibit pathological homogenization as a method of state-building.