In the light of NATO's humanitarian war in Kosovo is it possible to understand or explain wars as an outcome of perceptions of rights? How did rights, be they divine rights in the Middle Ages, territorial rights in the eighteenth century, or human rights today, become something that people are willing to fight and die for? To answer these questions, this book explores the linkage between concepts of rights and the practice of war in the international arena, describing how normative structures of rights have shaped different practices of war from medieval to modern times, through the lens of social constructivism.