The concept of security mean different meaning to some but for the most, security implies freedom from threats to core values (for both individuals and groups). For instance, during the cold war much of security was dominated by national security, which was largely construct for the military uses. In this period, the main area of interest was military capabilities for the states and how can we defend us for threats to our national security. however, more recently the idea of security includes political, economic, societal, environmental as well as military aspects, and that is also defined in broader international terms. National interests are a core security concern, the state system determinant the state behaviour and security equated with interest.
For realists, ‘no state will sacrifice its interests top serve the large community'(Frankel 1996: xv). In another hand, security is seen as a threat to the nation states. For realists, there is no higher government due to anarchic state and thus believe that the ultimate concerns for states is not for power but for security. It also the state is seen as protectorate of the populace against threats from potential enemies on its borders. Tradition security is often seen as them vs us based on different nationalities, cultures and ethics or race. During the cold war, many states throughout the world begun to changed their mindsets of security after end of world war two, as united states was able to develop and use a nuclear weapon in a form of atomic bombs, the scale of the destruction of these bombs were huge and these bombs had ability to destroy cities just by one single bomb. These bombs had changed the nature of welfare and security.
The most significant ways which nuclear weapon changed military security relates to the number of actors involved as more states begun to developed these weapons across the globe, because it was seen as if state possession nuclear weapons, it means that security is achieved by insecurity.