Realism is a school of thought that explains international relation in terms of power. The exercise of power by States towards is called politics. Politics is the distinction between politics within a state and politics outside a state, because the state is assumed to have sovereignty, that is the government having structure, rule of law and a hierarchy. Realism can be understood as a body of theories and related arguments about how the world works.
One of the principles of how realism works on the aspect of international arena is groupism, where human beings need groups to survive because individuals are weak The most important human group are nation-states and nationalism are the source of ingroup cohesion. Secondly, egoism, people are self-interested as it is rooted in the human nature. Power centralism, politics is all about power and it is the fundamental feature. Realist assumes that international relation can be best explained by the choices of states operating as autonomous actors rationally pursuing their own interest in an international system of sovereign states without a central authority.
Another proposition is that a nation can only advance its interests against the interests of other nations;this implies that the international environment is inherently unstable.Whatever order may exists breaks down when nations compete for the same resources,for example, and war may follow. In such an environment,the realists argue, a nation has only itself to depend on.Structural realism or neorealism is a theory that deals with the importance of power in the stance of international relation, this was outlined by Kenneth waltz who was a believer of defensive realism described in his book that the world is in anarchy that there is no sovereign and basically every state is dependent on themselves called self-help.
Another important theoretical preposition about international relation is balance of power in which state will keep dangerous concentration of power by building up their own capabilities both internally and external balancing. Political realism works to find out how power is shared across the different countries and how the international system works.Its main focus is on power. It can be in domestic as well as international system. In domestic system it talks about politicians while in the international system it talks about nation states descriptive political realism commonly holds that the international community is characterized by anarchy, since there is no overriding world government that enforces a common code of rules realist tend to see military force as the most important element of national power. They believe that international system exists in a state of anarchy.
Alliance play a key role in the balance of power. Building up one’s own capabilities against rival is a form of power balancing but forming an alliance against a threatening state is more effective. During the cold war, the united states surrounded Soviet Union with military and political alliances to prevent soviet territorial expansion. Alliances can shift rapidly, with major effects on power relations. The world’s main alliance, including NATO face uncertain roles in the changing world order.In order to understand the foreign policy, the neoclassical realism plays an important role to understand the working of international system.