This paper looks at the concept of collective security and how it has been operationalized from the early times of the Catholic Church, to the Concert of Europe, its application in the League of Nations and in the United Nations. The main trust of this paper focuses on the differences in the application of collective security by the United Nations Security Council and its relevance in today’s power politics.
 
Collective Security as an institutionalized mechanism for the maintenance of international peace and security has reduced tensions among states in the international community. It has done much by providing the framework for keeping conflicts from becoming major threats to international peace. As Palmer and Perkings pointed out, for Collective Security to be effective, it must be strong enough to cope with aggression from any power or combination of powers, and it must be invoked if and as aggression occurs.
The direction of the United Nations Collective Security system has always been dictated by the world big powers especially the five permanent members of the UN Security Council. Small and medium powers feel left out in the Collective Security arrangement as they can only benefit from the system only when the interests of any of the “big gives” especially the United States are at stake. However, its weakness does not dismiss the system as wholly unuseful.
This paper focuses on the concept of collective security and the different ways this concept has been applied in the international system, its significance and relevance.