Realism is based on international politics. Different theories however explain different concepts and propositions concerning realism but the basic ones that are shared by the different theorists are that the international systems are not hierarchical but anarchical, states are primarily the actors in the political systems and that states act to pursue their own interest which is either defined as power according to the offensive and classical realism, and state security according to the defensive realism. The key concepts of realism therefore are anarchy, national interest in terms of power and security and state as actors in international politics. Classical realist explains that the state is the main actor in international politics. The authority of the states is considered as the highest authority that has ever been into existence. The states are however likely to remain in this state over time. International politics have a difference when in comparison with the politics within the domestic boundaries. International states therefore are not expected to be treated as individual people. The emphasis of realism is to consider the role of these states in the international relations and view them as the sovereign states as the monopolists over the use of force which is focused on the behavior of the state.It also focuses on the states independence with every state being dependent on its own self. The emphasis is based on the survival of these states which is based on power.