Military alliance can be considered as an “embryonic” form of collective security: when states unit and allow access to their own security in order to promote and defend their national interests. From the Greek cities to the game of alliances of the Thirty Years War, from the Holy Alliance to the Entente (Triple Alliance), collective security was historical one and in its essence, was a system of alliances and guarantees, whereby governments provided mutual commitments in order to unite to face external threats and to support each other in case of an attack against one of them. In this context, the article focuses on the evaluation of the transformation of the nature of military alliances and their role after the Cold War. Particular attention is paid to the historical evolution of the process of formation of the system of alliances on the European continent and other defence and security structures of the contemporary stage. This allows us to determine whether alliances present stabilizing or destabilizing factor in the international order, where in the context of globalization the correlation between national and international security is increasingly emphasized. That is, states as a response to the actual risks and threats understand the necessity of multilateral collaboration in order to manage them.