Since the 1980s the number of the peace operations organized by the United Nations has steadily increased. Furthermore, regional international organizations have initiated an unprecedented number of peace missions. In 2003 the European Union Police Mission (EUPM) was dispatched to Bosnia. It was the European Union’s first operation since the introduction of the European Security and Defence Policy (ESDP). Since then the European Union has been on the frontline of peacekeeping and peacebuilding throughout the world. During this time, the principles, rules, and practices of multilateral security have changed under the pressure of new conditions and problems. This book is about the ESDP operations in the context of the current change in multilateral security and peace operations. The European Union and member governments have chosen multilateralism as the cornerstone of the EU’s international action. In security affairs, this choice has been implemented by building the European military and civilian capabilities of crisis management and conflict resolution. When these capabilities became operational, and ESDP forces were deployed on the ground, the EU’s peace operation organizers and commanders as well as the EU’s foreign and defence policy-makers became important actors in a complex, fluid, and tremendously important process, the transformation of peacekeeping, that has been in progress for the last 30 years. The original practice of UN-organized intervention for the sake of controlling truces and interrupting violence has been changed by the adoption of new forms of intervention that have given existing practices an unpredicted turn. Consequently, this book proposes, for students of peace operations in general and for students of the European Security and Defence Policy in particular, to analyse one, the worldwide experience of major changes in peace operations like the mounting number of regional, organization-led operations, the emergence of new peacekeeping and peacebuilding actors, and the extension of peace mission tasks, and two, the experience of ESDP operations and their concomitant problems such as the amalgamation of national security and defence standards, the combination of different foreign policy goals, and relations with the objectives and plans of the United States and NATO.