This study examines the evolution of the Common European Security and Defence Policy (CESDP) of the European Union before and after the Saint Malo Declaration of December 1998. The co-operation in foreign policy and security matters has always been a corollary element to the economic co-operation since the beginning of the European Integration process. Within this context this study argues that the conducting of co-operation in this field within the framework of European Community/European Union (EC/EU) was dependent on the national actors, the internal community/union factors, and the external dynamics. It is also asserted that, the European political co-operation is based on, on the one hand, the intergovernmentalist method of decision-making and implementation process, and on the other to the incrementalism through which the Member States could reconcile their diverging interests, which represent continuity within the EC/EU. The Saint Malo constitutes one of the momentous events in the trajectory of European foreign policy, security and defence co-operation, which launched the essentials of the CESDP. Within this framework, this study will analyse how a legally unbinding document has been incorporated into the legal framework of the European Union and consequently became the part of the acquis. Furthermore, the policies of France, Britain, and the United States within the process of establishment of the CESDP will be examined. Then, this thesis argues that, Saint Malo has initiated a ground for renegotiation of the terms of transatlantic relationship, which culminated in the redefinition of global roles and responsibilities of Americans and Europeans.