'Peace' is often simplistically assumed to be war's opposite, and as such is not examined closely or critically idealized in the literature of peace studies, its crucial role in the justification of war is often overlooked. Starting from a critical view that the value of 'restoring peace' or 'keeping peace' is, and has been, regularly used as a pretext for military intervention, this book traces the conceptual history of peace in nineteenth century legal and political practice. It explores the role of the value of peace in shaping the public rhetoric and legitimizing action in general international relations, international law, international trade, colonialism, and armed conflict. Departing from the assumption that there is no peace as such, nor can there be, it examines the contradictory visions of peace that arise from conflict. These conflicting and antagonistic visions of peace are each linked to a set of motivations and interests as well as to a certain vision of legitimacy within the international realm. Each of them inevitably conveys the image of a specific enemy that has to be crushed in order to peace being installed. This book highlights the contradictions and paradoxes in nineteenth century discourses and practices of peace, particularly in Europe.