That democracies do not wage war against each other is now a well-documented pattern of international politics. However, our theoretical knowledge of this so-called democratic peace is limited. We do not know what impedes democracies from fighting fellow democracies, even though they fight wars against (perceived) non-democracies. This volume contributes to the debate by way of classifying and synthesizing different theoretical accounts of democratic peace at the analytical level of the state and the intern ational system. It digs deep into the workings of the democratic political system and the orientations of its foreign policy-leaders which culminate in collective action on the international arena. A central theme is that processes of integration û taking place both within as well as among democracies û lead to the formation of a common identity: Democracies äconstructô their äfriendsô and äfoesô, basing their judgment on the way other states resolve their domestic conflicts. This argument is supported by a discussion of conceptual, methodological and epistemological problems of democratic peace. The volume concludes with a presentation of policy recommendations and a short summary in German.