Against the background of the changing nature of contemporary armed conflict, the monograph analyzes the transformation of international peace operations over the past two decades and a half: its quantitative expansion, doctrines’ evolution, diversification and the changing characteristics of peace operations and of their participants. It establishes, that the international community increasingly intervenes into intra-state armed conflicts and crises for the purpose of their settlement and management. Alongside the United Nations, regional organizations, in the first instance the European Union, NATO and the African Union, are taking an increasingly active part in these activities. The monograph establishes a growing importance of international peace operations as a regional security governance tool. It analyzes current trends in developing inter-institutional collaboration among the United Nations and relevant regional actors as regards the maintenance of international peace and security: the institutionalization of their collaboration, and the practicing of various options of cooperative deployment of peace operations. It analyzes the Russian Federation’s contribution to contemporary international peace operations.