The great majority of today's wars take place within rather between states and are often explained and justified by participants as the result of deep and ineradicable differences between 'them' and 'us'. The contributors to this book, whose disciplinary backgrounds include history, political science, international relations and anthropology, explore the growing importance of such 'ethnic' differences in a world that is also becoming more unified, politically, economically and culturally. They discuss the causes of internal war, the techniques used by nationalist politicians and intellectuals to turn ethnicity into a powerful political resource, the response of the UN and of non-governmental agencies to such 'complex' political emergencies as those in former Yugoslavia and Somalia and the constitutional strategies that can be used to acknowledge and accommodate ethnic diversity.