Introduction. This paper analyzes the history of development of the European Union’s political and military cooperation. The author gives an in-depth review of the origins of the European integration, its reasons and key political figures who played the crucial role in this process. The author shows that the establishment of cooperation between West European countries right after 1945 dealt with projects that were not implemented. Much attention is paid to the activities of the Western European Union (WEU) that played a considerable role in shaping the Common Foreign and Security Policy of the European Union. The article also presentshow different the members of the European Union are, how the views of the European countries vary in many areas and how difficult it is to coordinate the positions of the member-states on important issues concerning the foreign, security and defense policy of the European Union.Materials and methods. Building on the system analysis of the theories of international relations, international integration and the materials of related sciences such as political and conflict resolution studies the author considers the development stages of the European countries’ political and military collaboration from the establishment of the EuropeanDefense Community to the European Political Cooperation.Results. Proceeding from the results of the analysis the author concludes that the activities aimed to build military and political collaboration of the European states had laid a solid foundation to establish the second pillar of the EU - the Common Foreign and Security Policy (CFSP) by the time the Maastricht Treaty was signed in 1992.Discussion and conclusions. The materialsof this paper describe the stages and historicalroots of the development of the military and political collaboration of the European countries. Complexities and contradictions that are inherent in this process explain the challenges the EU’s current foreign, security and defense policies have to face.