International relations

• 1. Introduction

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  International relations is the academic discipline that tries to make sense of why states go to war, how they cooperate, and what holds the world together when nothing formally compels it to hold. Picture the ancient Sumerian city-states of 3,500 BC, jostling and negotiating across the flood plains of Mesopotamia. Scholars Barry Buzan and Richard Little identified those interactions as the first fully-fledged international system on record. Yet for millennia, no university offered a formal degree in studying such dynamics. That changed in 1919, when Aberystwyth University in Wales established the world's first professorship dedicated to international relations. Who funds a chair like that, and why? What theories compete to explain whether states are destined to fight or capable of lasting peace? And what happens when the old categories of nation, sovereignty, and power no longer seem to fit the world as it actually operates?

• 2. From Westphalia to the Nation-State

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  The Peace of Westphalia in 1648 is often treated as the origin point of the modern state system. Before it, European political authority rested on a vaguely hierarchical religious order. Westphalia began to shift that, though scholars note it still embodied layered systems of sovereignty, especially within the Holy Roman Empire. A more decisive marker, according to many historians of international law, is the Treaty of Utrecht of 1713, which more clearly established that sovereigns had no internal equals within their territory and no external superiors outside it. Those twin principles still underpin the international legal order today.

  The period from roughly 1500 to 1789 saw multilateralism and formal diplomacy take shape alongside increasingly independent sovereign states. Then the French Revolution introduced a new and explosive idea: that the citizenry itself, defined as the nation, was sovereign rather than the monarch or the nobility. A state built on that principle became a nation-state, with republic increasingly used as its synonym. Germany and others developed an alternative model grounded not in civic identity but in ethnic-linguistic terms, positing that all speakers of one language should belong to a single state. Neither model has ever been fully realized. Across Europe today, few states conform to either definition: many retain royal sovereigns, and almost none are ethnically homogeneous.

  The European nation-state model was exported globally through colonialism and what contemporaries called the standards of civilization, and the contemporary international system was only completed through decolonization during the Cold War. Even then, the picture is complicated. Some states are described as pre-modern, never having fully adopted the nation-state form; a handful are considered post-modern, having moved beyond insistence on full sovereignty. Jean Bodin laid out a foundational account of sovereignty in his Six Books of the Commonwealth in 1576, describing it as absolute power over a territory, limited only by the sovereign's obligations toward other sovereigns and individuals.

• 3. Building the Academy

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  Paul Samuel Reinsch established international politics courses at the University of Wisconsin in 1899, more than two decades before the discipline had a name. Columbia University followed in 1910. But the field's formal birth is dated to 1919, when the Woodrow Wilson Chair was established at Aberystwyth, University of Wales, endowed by David Davies and first held by Alfred Eckhard Zimmern. That same year, Georgetown University's Walsh School of Foreign Service opened as the oldest continuously operating school for international affairs in the United States.

  By 1920, four universities taught courses on international organization. Momentum accelerated in 1927, when two landmark institutions opened almost simultaneously. The London School of Economics launched its department of international relations at the behest of Nobel Peace Prize winner Philip Noel-Baker, the first institute to offer a wide range of degrees in the field. That same year, the Graduate Institute of International and Development Studies was founded in Geneva, Switzerland, explicitly to train diplomats for the League of Nations, making it the first university entirely dedicated to IR.

  Georgetown graduated its first class of the Master of Science in Foreign Service in 1922. The University of Chicago's Committee on International Relations conferred the first research graduate degree in the field in 1928. The Fletcher School of Law and Diplomacy, a collaboration between Tufts University and Harvard University, opened in 1933 as the first graduate-only school of international affairs in the United States. Canada entered the picture in 1965, when Glendon College and the Norman Paterson School of International Affairs became the first Canadian institutions to offer undergraduate and graduate programs respectively. The creation of the Montague Burton professorships at LSE and at Oxford gave further institutional weight to the field as it matured through the mid-twentieth century.

• 4. Realism and Its Rivals

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  Thucydides wrote his History of the Peloponnesian War in the 5th century BC, and realist scholars have been citing it ever since as a foundational text. Richard Ned Lebow has argued that reading Thucydides as a realist is a misinterpretation of a more complex political message, but the debate itself says something important about how contested the field's intellectual lineage is. Machiavelli's The Prince, published in 1532, and Hobbes' Leviathan are also drawn into the realist canon, though neither author would likely have classified himself a realist in the modern sense.

  Realism's core claim is that the international system is an anarchy: no overarching authority exists to restrain states, so each pursues military capability, economic power, and diplomatic leverage to protect its own survival. States are treated as unitary, rational actors; international organizations are seen as tools states use to serve their own ends, with little independent influence. Major theorists associated with realism include E. H. Carr, Hans Morgenthau, Kenneth Waltz, Robert Jervis, Stephen Walt, and John Mearsheimer.

  Liberalism pushes back on that picture. Kant's 1795 essay Perpetual Peace is often cited as the intellectual wellspring of liberal IR theory. Kant argued that states, through deepening political and economic cooperation, would gradually form something resembling a world federation characterized by lasting peace. Woodrow Wilson and Norman Angell were early adherents after World War I. E. H. Carr gave liberalism its lasting nickname by dismissing it as idealism; later, Hans Köchler advanced a version focused on human rights as the basis of international law's legitimacy. Robert Keohane's 1984 book After Hegemony used insights from the new institutional economics to argue that the international system could remain stable even without a dominant hegemon, directly rebutting hegemonic stability theory.

  Constructivism entered the conversation when Alexander Wendt published a 1992 article in International Organization arguing that the anarchic structure realists treat as a fixed fact is actually socially constructed and reproduced by states themselves. His phrase, that anarchy is what states make of it, became a touchstone for an entire school of thought. Constructivists point to cases like European integration, where senior policymakers were socialized into a shared idea of Europe as a historical community and built institutions to match. Prominent constructivist scholars include Michael Barnett, Martha Finnemore, Ted Hopf, Peter Katzenstein, Kathryn Sikkink, and Alexander Wendt.

• 5. Critical and Feminist Turns

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  Post-structuralist theories of IR developed in the 1980s from postmodernist studies in political science. They focus on deconstructing concepts usually taken for granted in the discipline, such as power and agency, and examine how the way those concepts are constructed shapes international relations in practice. Feminist poststructuralist work, for example, has analyzed how women are constructed in wartime as innocent and civilian, and what that framing does to the politics of armed conflict.

  Carol Cohn's 1988 article Sex and Death in the Rational World of Defense Intellectuals argued that a highly masculinized culture within the defense establishment contributed to separating the practice of war from human emotion. Feminist IR emerged largely from the late 1980s onward, and the end of the Cold War in the 1990s opened space for broader questioning of traditional IR assumptions. The growing influence of feminist approaches within international policy institutions, such as the World Bank and the United Nations, reflects a more liberal feminist emphasis on equality of opportunity rather than a critical or poststructuralist one. Prominent feminist IR scholars include Cohn, Cynthia Enloe, Sara Ruddick, and J. Ann Tickner.

  Marxist theories reject the realist and liberal focus on state conflict or cooperation and treat the global economy as an integrated capitalist system pursuing capital accumulation. Colonialism, in this view, brought access to raw materials and captive markets; decolonization brought new opportunities in the form of economic dependence. Critical theory, associated with the Frankfurt School, applied that lens to questions of social change. Modern critical IR scholars such as Andrew Linklater, Robert W. Cox, and Ken Booth focus on emancipation from the nation-state as a human need. Dependency theory extends this analysis, arguing that developed states appropriate developing ones through banking, security, and trade agreements, as well as through the informal channels of financial advisors, relief aid workers, and multinational corporations.

• 6. Power, Polarity, and the Modern System

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  Kenneth Waltz's article The Stability of a Bipolar World laid out the case that the two-superpower structure of the Cold War was a source of stability. When the Soviet Union collapsed in 1991 and the United States emerged as the sole superpower, Waltz's thesis faced a direct test. William Wohlforth's 1999 article The Stability of a Unipolar World responded directly to Waltz, arguing the opposite. Robert Gilpin's hegemonic stability theory also addressed unipolarity, positing that dominance by a single pole produces stable outcomes through mutual gains for both the hegemon and other states.

  China's ascent complicated that picture. It became the world's second-largest economy in 2010. Debate has continued over whether China qualifies as a superpower, with analysts noting that its strategic forces remain limited in their capacity to project power beyond its region, and that its nuclear arsenal of 250 warheads compares to more than 7,315 held by the United States. Power transition theory, associated with A. F. K. Organski, adds another layer: it holds that a rising great power is likely to challenge an established hegemon after a certain period, potentially triggering a major war. Organski grounded this argument in historical patterns during British, Portuguese, and Dutch hegemony, and analysts have applied the framework to tensions between the United States and China in the early twenty-first century.

  The concept of sovereignty itself has roots older than any of these debates. Jean Bodin described it in 1576, and throughout world history groups have lost or lacked it: African nations before decolonization, and Iraq during the occupation following the Iraq War, are cited as examples. Non-state actors have further complicated the picture in the 21st century. Al-Qaeda is cited as a concrete case of a non-state actor that significantly altered how both states and other non-state actors conduct international affairs, illustrating that the international system is no longer monopolized by states alone.

• 7. Tools and Institutions

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  Carl von Clausewitz defined war as the continuation of politics by other means, and that definition still anchors how international relations scholars think about armed conflict. Below the threshold of war, states have assembled a toolkit that includes diplomacy, economic sanctions, the mobilization of international shame, and the conditional extension of benefits. The European Union's enlargement policy, under which candidate countries can only join if they meet the Copenhagen criteria, is one example of how benefits function as a lever in international negotiation.

  Human rights NGOs such as Amnesty International and Human Rights Watch have deployed the naming-and-shaming mechanism as a distinct tool, attempting to alter state behavior through public exposure at the international level. Amnesty International's characterization of Guantanamo Bay as a Gulag is cited as a prominent example. The UN Commission on Human Rights used its 1235 procedure to publicly expose state human rights violations; the current UN Human Rights Council had not yet employed that mechanism as of the source text.

  The United Nations describes itself as a global association of governments facilitating cooperation in international law, international security, economic development, and social equity. The Organisation of Islamic Cooperation, with 57 member states, frames itself as the collective voice of the Muslim world. Beyond those generalist bodies, the international institutional landscape includes regional security arrangements, economic institutions such as the World Bank and the International Monetary Fund, and international legal bodies. Stephen Krasner's definition of regimes as principles, norms, rules, and decision-making procedures around which actor expectations converge in a given issue-area remains the most commonly cited framework for understanding how cooperation persists even when no authority compels it. Regime theory holds that trade, human rights, and collective security all provide working examples of that cooperation in practice.