The European security environment which prevails in the early 21st century has evolved over more than twenty years, with transnational threats emerging, new security actors active at sub-state and international level and a changing discourse which focuses increasingly on human security and a comprehensive approach to crisis management. UCD SPIRe Associate Professor Ben Tonra recently published a co-authored paper entitled European Security in the 21st Century, through the IIEA, which examines the origins of the current security environment in Europe, traces some of the major conceptual debates associated with the recent evolution, describes the multilateral institutional framework and, finally, comments on the contribution of Ireland. Professor Tonra, Jean Monnet Professor of European Foreign, Security and Defence Policy and Associate Professor of International Relations at University College Dublin, is Project Leater for the IIEA group. This paper launches the IIEA European Security and Defence Series, and offers a broad outline of the policy sector as a whole as an introduction to the series. The series will continue over the coming months with further briefing papers and factsheets on specific aspects of European security and defence policy. Download IIEA European Security and Defence Series: European Security in the 21st Century here.