Nationalism has been identified as one of the most pressing of global problems, exacerbating ethnic conflicts and encouraging war. It is also seen as essential to defining the rights of democratic citizenship and a source of inspiration and social solidarity. Drawing on examples from Eritrea, Yugoslavia and China to France and Germany, this text seeks to clarify the way in which national boundaries and identities became central to the moden era, how they relate to the development of state power, and how a host of different social movements and government policies try to make use of them. At the same time the author also challenges attempts to "debunk" nationalism that fail to grasp why it maintains its power and centrality in modern life.