International relations is a multi-disciplinary field that draws on insights from sociology, philosophy, economics, law and history, in addition to political science. It is concerned with explaining and understanding the complex interactions between nation-states. It also examines the role of non-state actors, such as multinational corporations or NGOs (nongovernmental organisations), in global politics.
One of the most important theories in IR is realism. Realism holds that all state actors know their preferences, are able to order them, and have some degree of power—military, economic, or diplomatic—that they are willing to project in the world. This power can influence the distribution of resources and the overall direction of international systems. For example, if one country increases its military spending, other countries may increase their own defense budgets, creating a spiral of insecurity that can lead to war.
Those who subscribe to this theory believe that cooperation is unlikely and conflict is the norm in international affairs. Some, such as neo-liberal Kenneth Waltz, developed the concept of polarity to explain this situation. He argued that states engage in balancing and bandwagoning to gain leverage over other states.
Other theories focus on specific institutions or individuals as explanations for state behavior. For instance, feminist scholars emphasize the way that men disproportionately dominate global politics and often overlook the impact of political violence on women and children. They also point out that state leaders tend to ignore their own role in the spread of terrorism and other threats.