The idea for this book was born in the summer of 2017. But even before, the observation that the use of force throughout history needs justification and that the justification of war interacts with the construction of international order had become a recurring and increasingly central topic in our research projects at the Peace Research Institute Frankfurt and in our seminars taught at Frankfurt’s Goethe- University. Lothar encountered the justification of war as a theoretical endeavour and a political practice in the context of his engagement with the modern project of achieving peace through law, which in our view still is to be defended, by being critically examined, against the ‘hard facts’ of international anarchy which Realists of all walks of academic life and life in general like to refer to. At the same time, Hendrik was engaged in writing well- placed articles and a historic study on the ‘myth of the “free right to go to war” ’ (which, of course, sometimes suffered under the workload of producing the present volume). Our discussions led to the idea of engaging with the role of norms in political discourses on the legitimation of violence under a broader geographical, historical, and disciplinary perspective— from past(s) to present(s), as the book’s subtitle indicates. For it seemed conspicuous that war has never been and probably will never be waged without recourse to norms, as we and our authors emphasize in this volume. So the contributions of the book follow, in different ways, the assumption that the history of war is also a history of its justification and interacts with what is recognized as international order.