Realism

Realism is the oldest and most influential school of thought in international relations theory. Its central claim is deceptively simple: in a world without a supreme authority above states, power is the ultimate currency of politics, and survival is the primary goal of every nation.

The Anarchic System¶

The foundation of realist thought rests on a single structural observation: there is no world government. Unlike domestic politics, where a state monopolizes legitimate violence and enforces contracts, the international system lacks any comparable authority. This condition—what realists call anarchy—does not mean chaos or disorder. It means that states cannot appeal to a higher power when threatened. They must provide for their own security.

This structural reality produces predictable behaviors. States arm themselves, form alliances, and view each other with suspicion—not necessarily because their leaders are evil, but because the system rewards caution and punishes naivety. A state that fails to attend to its security may not survive to regret the oversight.

Core Assumptions¶

Realist theory rests on several interlocking premises:

States as primary actors. While corporations, international organizations, and non-state groups matter, realists insist that states remain the decisive players in world politics. Only states command armies, control territory, and possess sovereignty.

Rationality under uncertainty. States are assumed to act rationally in pursuit of their interests, though they operate with incomplete information about others’ intentions. This uncertainty itself generates security competition.

Power as the medium of politics. Influence in international affairs flows from material capabilities—military force, economic resources, technological advantage. Ideas and institutions matter, but only insofar as they reflect or mask underlying power distributions.

Self-help as the organizing principle. Because no authority guarantees their survival, states must ultimately rely on their own capabilities. Alliances are temporary expedients; today’s partner may be tomorrow’s rival.

Classical and Structural Variants¶

The realist tradition encompasses several distinct schools:

Classical realism, associated with Hans Morgenthau and rooted in the writings of Thucydides and Machiavelli, locates the drive for power in human nature itself. Leaders seek dominance because humans are inherently power-seeking creatures. Morgenthau’s Politics Among Nations (1948) remains the foundational text, arguing that the “concept of interest defined in terms of power” provides the key to understanding foreign policy across cultures and eras.

Structural realism (or neorealism), developed by Kenneth Waltz in Theory of International Politics (1979), shifts the explanation from human nature to systemic structure. States seek power not because leaders are ambitious but because the anarchic system compels them to do so. Even a world of status quo powers would experience security competition, since none can be certain of others’ future intentions.

Within structural realism, a further division exists:

Defensive realism (Waltz, Stephen Walt) argues that states generally seek security rather than power maximization. Expansion is often counterproductive, provoking balancing coalitions that leave the aggressor worse off. The system punishes overreach.
Offensive realism (John Mearsheimer) contends that the only reliable path to security is hegemony. Since states can never be certain they have “enough” power, rational actors seek to maximize their relative position whenever opportunity permits. Great powers are “power maximizers, not security maximizers.”

The Security Dilemma¶

One of realism’s most powerful concepts is the security dilemma: actions taken by one state to enhance its security—building weapons, forming alliances—often make other states feel less secure, prompting them to respond in kind. The result is an arms race or heightened tensions even when no party intended aggression.

The Cold War exemplified this dynamic. The United States and Soviet Union each viewed the other’s military buildup as threatening, leading to a nuclear arms race that neither truly wanted but neither could safely avoid. The security dilemma helps explain why peace can be fragile even among states with no desire for conquest.

Realism and Great Power Politics¶

Realism finds its natural application in the study of great power competition. The rise of China and the persistence of Russian revisionism have renewed interest in realist frameworks after the post-Cold War period’s brief flirtation with liberal internationalism.

For offensive realists like Mearsheimer, China’s ascent poses a structural challenge to the United States regardless of Beijing’s ideology or intentions. A peer competitor in Asia threatens American primacy, and Washington will resist that challenge just as it resisted Soviet power. The nature of the regimes matters less than the distribution of capabilities.

Defensive realists offer a more nuanced view. China’s rise need not lead to war if both sides exercise restraint and avoid the destabilizing effects of the security dilemma. Geography—the Pacific Ocean—provides natural buffers that make conquest difficult. But even defensive realists acknowledge that great power transitions are historically dangerous.

Critiques and Limitations¶

Realism’s parsimony is both its strength and weakness. Critics charge that the theory:

Underestimates cooperation. International institutions, trade interdependence, and shared norms have enabled sustained cooperation among states, particularly in Europe since 1945. The European Union’s very existence challenges the realist assumption that anarchy precludes deep integration.

Neglects domestic politics. Realism treats states as unitary actors, but foreign policy emerges from domestic political contests, bureaucratic interests, and leadership psychology. Democracies may behave differently than autocracies; populist leaders may reject rational calculation.

Fails to explain change. If the system’s structure is timeless, how do we account for transformations like the peaceful end of the Cold War or the spread of norms against territorial conquest?

Morally troubling. By treating power politics as inevitable, realism can become self-fulfilling—a justification for aggression rather than merely its explanation.

Realists respond that their theory describes the world as it is, not as we might wish it to be. Cooperation occurs, but it remains fragile and dependent on underlying power balances. The Soviet Union collapsed not because of ideas but because it could no longer compete economically and militarily. And the relative peace since 1945 owes much to American hegemony—a distribution of power, not a transformation of politics.

Contemporary Relevance¶

Realism’s relevance surged after 2014, when Russia’s annexation of Crimea and China’s assertiveness in the South China Sea shattered assumptions about the “end of history.” The geopolitical lens returned to the center of strategic discourse.

Today, realist concepts inform debates about:

Great power competition between the United States and China
NATO expansion and the war in Ukraine
The limits of international institutions in restraining revisionist powers
The balance-of-power in the Indo-Pacific
Deterrence and the management of nuclear risks

Whether one accepts realism’s worldview or not, its concepts—anarchy, the security dilemma, the balance of power—remain indispensable tools for understanding international politics. Even critics must engage with realism, if only to explain why they believe the theory wrong.