The war by Russia against the Ukraine will be of serious consequences under a number of political categories. This book is devoted to the study of changes brought about by the war. To set out, it starts with a recollection of the development towards the war in the two decades prior to February 2022. It then asks for the renewal of specific political theories, among them political realism especially, on behalf of the war. Also it studies the consequences for the relevance of international war (jus ad bellum and jus ex bellum) and for the international standing of Western democracies.