This thesis analyses the development of the European Union into a Union focusing on a Common Security and Defence Policy. As the Member States have kept peace among each for more than sixty years now, the European Union must be considered worldwide as a unique peace project. This success must be attributed mainly to the efforts of the European Union.Considering the development of the Union from the Dunkirk Treaty to the creation of the European Defence Agency, the massive changes in Europe since 1947 become quite obvious. Each period provided different reasons for European integration. In the recent past, however, hostile confrontations and warfare have been responsible for the accelerated consolidation of the process. The bloody wars on the Balkans during the 1990ies proved to be a crucial factor in this development. Just at a point when reactions were in dire need, the Union demonstrated its incapability in the defence and security sector.In 2009, however, enemy stereotypes have been given up, whereas the first two defence alliances reflect a deep-rooted fear of an expanding USSR and a reconsolidated Germany.It goes without saying that cooperation in the field of the Common Security, Foreign and Defence Policy will be indispensable to safeguard peace and security in Europe.The creation of the European Defence Agency is a milestone towards a real Common Defence Policy.