According to the Stanford Encyclopedia, it defines realism as, the view of international politics that stresses its competitive and conflictual side. That being said implies that the international relations theory of realism feeds off of the ideals of power and independence. Realist assumes that actors’ actions are driven by their self-interest, which is true but their foundation is to establish and maintain dominance. For an actual realist, hard power such as military defense and capital are the most important things to them. Realists believe that it is in our human nature to become selfishness, for power.
The first principle of realism is that the state is the fundamental actor in international relations. There are other non-state actors, such as individuals and organizations such as your non-governmental organizations (NGOs) such Red Cross, World Wildlife Fund, etc. These actor’s powers are limited when it comes to impacting realism. For realist national interests, especially during times of war, the head of state will choose the independent dominant strategy for that state. Decision-makers are the rational actors in the sense that rational decision-making leads to the pursuit of the national interest. Here, taking actions that would make your state weak or vulnerable would not be rational. Realism suggests that all head of states, no matter what their political background is, recognizes that when he or she attempts to manage their state’s affairs in order to survive in that competitive environment. Realist do not support the liberal interest of peace, but rather that states should only resemble self interest which is more rational than being cooperative.
Finally, states live in a context of anarchy that is, in the absence of there being a central government. Realist support the ideology of self-help, where they can’t trust anyone but themselves. In our own states we typically depend on first responders or people who are called to action like our police forces, militaries, courts and so on. There is an expectation that these people who are put in these positions will act in response. Internationally, there is no clear expectation of anyone or anything ‘doing something’ because there is no established hierarchy. Therefore, states must ultimately only rely on themselves.