This thesis is a study on the European Union’s evolving Common Foreign and Security Policy (CFSP). It aims to analyze the evolution of the Common Foreign and Security Policy of the European Union from its Cold War origins with particular consideration on post-Cold War developments. Emphasis will be put on the divergences of ideas resulting from the internal dynamics of the Union that shape the security policies of the EU. In this study, the major question, which will be tried to be answered, is how have the divisions within the EU, which result from the internal dynamics of the EU, affected the evolution of the Union’s security policies. This study argues that the divisions within the European Union have so far prevented the Union from pursuing an effective Common Foreign and Security Policy. Cooperation with NATO in the field of crisis management would provide the EU with military assets and capabilities which are required for an effective military crisis management mission. At the same time, this study argues that an effective crisis management in the EU can be achieved by covering both military and civilian aspects of crisis management in a balanced way.