After the end of World War II leaders of the West European countries had realised the necessity to create new security frameworks, thus making the security of the continent the concern of the Europeans themselves. However, immediately after it had been formed the North Atlantic Alliance, as a trans-Atlantic defence shield against the danger from the "communist East", became the central security component in Europe. Just after the end of the Cold War and disappearance of the "danger from the East" the European leaders initiated the process of creation of the new European defence system. The system would be designed in such a way not to jeopardise the position of the NATO, improving at the same time the security and stability in the continent. In the first part of the article the author considers the course of European integration in the second half of the last century that proceeded through creation of institutions preceding the establishment of the European Union. During the period of creation of this specific form of action performed by the European states at the internal and international levels, the deficiency of integration in the military field was notable. In that regard, the author stresses the role of the Western European Union as an alliance for collective defence of West European countries. The second part of the paper discusses the shaping of the EU security component through the provisions on the Common Foreign and Security Policy, which are included in the EU agreements. The Maastricht Treaty defined the Common Foreign and Security Policy as an instrument to reach agreement by member states in the defence field. The Amsterdam Treaty confirmed the role of this mechanism expanding the authorities resulting from it. The Treaty of Nice supplements the existing mechanism by a new military and political structure that should help implement the decisions made by the European Union institutions in the military field. In the third part of the article, the author presents the facts concerning the establishment and internal organisation of the Eurocorps. The creation of this military formation took place in early 1990s and was initiated by the two states of "the old Europe" - Germany and France. The authors also emphasises that the establishment of this formation is the first step towards creation of the armed forces in Europe. The fourth part of the paper treats the Rapid Reaction Force that was established by the Helsinki Agreement (1999). It became operative in early 2003 and its basic aim is to prevent the outbreak of crises in the region and to improve stability in Europe. In spite of the opinions that the establishment of such a force is the skeleton for creation of the European armed forces, the author thinks that, at least in the near future, they will not be a rival to the NATO. In his opinion, their possible military missions will be carried out only when the alliance takes no interest in being engaged in them.