International relations as an academic discipline has developed through a variety of theoretical perspectives that aim to explain how states and other actors behave in the international system. These theories provide different lenses through which global politics can be understood, highlighting the dynamics of power, cooperation, conflict, and institutions. Theories of international relations are not only explanatory but also normative, as they suggest how states should act to achieve peace, security, or justice. Major schools of thought include realism, liberalism, constructivism, Marxism, critical theories, postcolonialism, feminism, and English School theory, among others. Each of these perspectives offers a unique interpretation of international relations and world history, shaped by particular historical contexts and intellectual traditions. Realism remains one of the oldest and most influential theories in international relations. Rooted in the writings of Thucydides, Machiavelli, and Hobbes, realism emphasizes the anarchic nature of the international system, where no central authority exists to enforce rules. According to realists, states are the primary actors, motivated by self-interest and the pursuit of power in order to survive. Classical realism highlights human nature as the source of conflict, while neorealism, associated with Kenneth Waltz, attributes conflict to the anarchic structure of the international system itself. States operate in a self-help environment where security dilemmas arise, and military power becomes a crucial tool for survival. From the realist perspective, international cooperation is fragile and temporary, as states ultimately prioritize their national interests. This framework has been used to explain both world wars, the Cold War rivalry, and ongoing geopolitical conflicts. Liberalism offers a contrasting perspective by emphasizing the possibility of cooperation and the role of institutions, trade, and democracy in mitigating conflict. Stemming from Enlightenment ideas of progress, liberalism argues that human beings and states are capable of rational cooperation. Economic interdependence, international organizations like the United Nations, and the spread of democratic governance are seen as mechanisms that foster peace. Neoliberal institutionalism, advanced by scholars like Robert Keohane, focuses on how international institutions reduce transaction costs, provide information, and create rules that stabilize cooperation among states. Liberalism is closely tied to the notion of the “democratic peace theory,” which suggests that democracies are less likely to go to war with one another. Historical developments such as the post-1945 institutional order, the growth of international law, and regional organizations like the European Union reflect liberal ideas in practice. Constructivism challenges the materialist assumptions of realism and liberalism by stressing the importance of ideas, identities, and norms in shaping international relations. According to constructivists like Alexander Wendt, the international system is not just structured by material power but also by shared understandings and social interactions among states. States act based on how they perceive themselves and others, and these perceptions are constructed through history, culture, and discourse. Constructivism emphasizes that anarchy does not have a fixed meaning; rather, it is what states make of it. For example, relations among democracies are characterized