Realism and Rationality: The Cold War Era of International Relations

After 1945, the study of international relations underwent a quiet revolution. The discipline that had once relied on diplomatic histories and moral arguments began to model itself on the natural sciences. Scholars wanted laws, evidence, and systematic explanation rather than opinion and anecdote. This shift, often called the scientific studies stage of IR (1945-1991), coincided almost perfectly with the Cold War. Two thinkers came to dominate this era: Hans J. Morgenthau, who built the case for classical Realism, and Kenneth Waltz, who reworked it into the more rigorous Neo-Realism. Together they made power, rationality, and the structure of the state system the central concerns of the field. Yet for all their analytical power, neither could foresee the event that ended the very period they sought to explain.

Why the discipline turned scientific 🔗

Before World War II, international relations was studied largely through history, law, and idealist hopes for peace. The failure of the League of Nations and the outbreak of a second global war discredited the idealism of the interwar years. Scholars wanted a tougher, more realistic way of explaining why states behave as they do.

At the same time, a broader movement was sweeping American social science. Behavioralism encouraged researchers to study political behaviour using quantitative methods borrowed from psychology and economics, replacing philosophy with the philosophy of science. The goal was to establish testable relationships between causes and effects rather than rely on description or moral judgement.

This scientific impulse reached international relations, though it never dominated the subfield as completely as it did domestic politics. The Correlates of War Project, founded at the University of Michigan in 1963, gathered large amounts of quantitative data and became a leading source for scholars studying the causes of war. The ambition was clear: treat world politics as a system that could be measured, modelled, and eventually understood through general theory.

Classical Realism: Morgenthau and the struggle for power 🔗

The intellectual anchor of this era was Hans J. Morgenthau, a German émigré scholar whose 1948 work Politics Among Nations: The Struggle for Power and Peace became the standard text in IR classrooms for decades. Having witnessed Germany under Hitler, Morgenthau was deeply sceptical of the idea that good intentions or international law could restrain states.

Morgenthau’s contribution is best captured in his six principles of political realism, which appeared as the opening chapter of his book and provided a clear intellectual foundation for the realist school. These principles framed how a generation of scholars thought about world affairs.

The core ideas of political realism 🔗

The first principle holds that politics is governed by objective laws rooted in an unchanging human nature, which makes it possible to build rational theories of politics. Because human nature does not change, the behaviour of states can be studied systematically rather than treated as random.

The most famous principle is the second: the key to understanding international politics is the concept of interest defined in terms of power. Morgenthau argued that statesmen think and act in terms of power, whatever the moral language they use to justify their decisions. As one analysis puts it, the national interest is primarily concerned with the military and economic capabilities and the balance of power that determine a state’s standing.

Morgenthau was also wary of moralism in foreign policy. He believed it was dangerous to identify the moral aspirations of one nation with universal moral law, because imposing a particular ideology on the world threatens international peace and security. For Morgenthau, the wise statesman judges a policy by a single question: how does it affect the power of the nation?

Neo-Realism: Waltz and the power of structure 🔗

For all its influence, classical Realism rested on assumptions about human nature that were hard to test scientifically. Kenneth Waltz set out to give Realism a firmer, more systematic footing. His 1979 book Theory of International Politics created the approach known as Neo-Realism, or structural realism, and it became the most assigned book in international relations graduate training at universities in the United States.

Waltz’s central move was to shift the explanation away from human nature and the internal character of states. Instead, he located the cause of state behaviour in the structure of the international system itself. Where Morgenthau looked inward at leaders and their drive for power, Waltz looked outward at the system that surrounds every state.

Anarchy and the distribution of power 🔗

The foundation of Waltz’s theory is anarchy. This does not mean chaos. It means the absence of a higher authority above states, since world politics is anarchic because there is no world government to settle disputes. In such a system, no state can be sure of another’s intentions, so each must look after its own security.

Within this anarchic order, states are treated as similar units that differ mainly in their capabilities. Waltz argued that system-level processes of socialisation and competition push states to behave in similar ways, regardless of their internal politics. A democracy and a dictatorship, facing the same structural pressures, will often act alike on the world stage. This is why Waltz rejected what he called reductionist explanations that focus only on the individual state.

The second key variable is the distribution of power, or what Waltz called polarity. The crucial question for Waltz was whether the system is dominated by one, two, or many great powers. He famously argued that a bipolar world, like that of the Cold War with two superpowers, was more stable than a multipolar one, because the two giants could manage their rivalry with relative predictability.

How Neo-Realism differed from classical Realism 🔗

The difference between the two thinkers is more than a technical detail. Both belong to the realist tradition that sees politics as a competition among self-interested actors. But Waltz’s neorealism departs from Morgenthau’s classical realism by trying to provide a scientific and structural account of power relations rather than one grounded in human nature.

Waltz borrowed from economics to make his point. He compared states in the international system to firms in a market, arguing that international systems emerge from the interaction of self-regarding units, much as markets emerge from competing firms. This analogy gave Neo-Realism the parsimony and rigour that the scientific age prized, allowing it to explain recurring patterns of war and peace with a small number of variables.

Strengths of the realist project 🔗

It is easy to see why these theories dominated the Cold War period. They matched the world that scholars saw around them: two superpowers locked in a tense, enduring rivalry, building arsenals and forming alliances in a constant balancing act. Realism explained the arms race, the logic of deterrence, and the formation of opposing blocs without needing to appeal to the personalities of individual leaders.

The theories also offered what the scientific age demanded. Neo-Realism in particular was praised for its parsimony and rigour, and it has been widely used to explain war and peace, making it one of the most influential IR theories of the twentieth century. A handful of clear assumptions could generate broad predictions about how states would behave. For a discipline trying to look more like physics than philosophy, this was a major achievement.

The great blind spot: failing to foresee the end of the Cold War 🔗

Then came 1989. The Berlin Wall fell, the Soviet bloc unravelled, and in 1991 the Soviet Union itself dissolved. Remarkably, this transformation happened largely peacefully, without the great-power war that realist logic might have led one to expect. The theories that had so confidently mapped the bipolar world had not seen it coming.

This became one of the sharpest criticisms of the realist project. Scholars noted that one of the main criticisms of neorealism is that it failed to predict the end of the Cold War, which arrived unexpectedly in the 1989-1991 period. A framework built to explain enduring superpower competition struggled to account for the voluntary retreat and collapse of one of the two poles.

Why structure could not explain the change 🔗

The deeper problem lay in what Neo-Realism deliberately left out. By focusing only on system structure and ignoring what happens inside states, the theory could not capture the role of ideas, leadership, and reform. Critics argued that omitting unit-level variables lowered the predictive capacity of neorealism, leaving it too static to account for big changes such as the peaceful demise of the Soviet Union.

The forces driving the Soviet collapse were largely internal: economic stagnation, the reformist “new thinking” of Mikhail Gorbachev, and a crisis of confidence within the leadership. These were exactly the kinds of domestic factors that Waltz’s structural theory treated as outside its scope. The system had not changed; the actor inside it had simply chosen to step back.

The realist reply 🔗

Realists did not concede defeat. Waltz himself argued that prediction was never the point. The defence is that neorealism aims to explain the logic of relationships in the international system rather than predict the behaviour of individual states at any given moment, so the theory has explanatory rather than predictive power. Other scholars, such as William Wohlforth, argued that the peaceful Soviet decline can in fact be explained by shifts in relative power, and that no social-science theory could realistically have predicted such a complex and unprecedented event.

Still, the episode left a lasting mark. The failure to anticipate the end of the Cold War opened the door for rival approaches such as constructivism and liberalism, which insisted that ideas, identities, and domestic politics matter as much as raw power. The scientific studies stage had given IR rigour and clear theory, but it also revealed the limits of explaining a world of human beings purely through structures and power.

What do you think? If a theory openly admits it cannot predict major events like the end of the Cold War, how useful is it as a guide to the future? And was the realist focus on power a clear-eyed view of how the world really works, or a blind spot that left the discipline unable to see change coming?

References

1. https://www.britannica.com/topic/political-science/Behavioralism
2. https://www.ebsco.com/research-starters/social-sciences-and-humanities/morgenthau-advances-realist-school-power-politics
3. https://nationalinterest.org/feature/trump-can-learn-morgenthaus-6-principles-political-realism-19481
4. https://polticsmania.wordpress.com/2016/10/13/morgenthaus-six-principles-of-political-realism/
5. https://en.wikipedia.org/wiki/Kenneth_Waltz
6. https://www.britannica.com/biography/Kenneth-N-Waltz
7. https://en.wikipedia.org/wiki/Theory_of_International_Politics
8. https://adambrown.info/p/notes/waltz_theory_of_international_politics
9. https://www.beyondintractability.org/bksum/waltz-theory
10. https://www.academia.edu/36972454/On_Idealism_and_Realism_The_Dissolution_of_the_Soviet_Union
11. https://www.gradeninjas.com/realism-and-the-end-of-the-cold-war/