The Realist Perspective: Power and National Interests in War

Why does war keep happening, even when almost everyone agrees it brings destruction and suffering? For realist thinkers, the answer is uncomfortable but straightforward: war is not an accident or a moral failure that can be fixed with better intentions. It is a recurring feature of a world where states must look out for themselves. Realism is one of the oldest and most influential schools of thought in international relations, and it treats power, fear, and survival as the real engines of global politics. This post explains how realists understand war, why they place national interest above ideals, and how classical and neo-realist thinkers differ in pinpointing the true cause of conflict.

What realism means in international relations 🔗

Realism is a school of thought that emphasises the competitive and conflictual side of international relations. Its roots run deep, often traced back to Thucydides’ account of the Peloponnesian War between Athens and Sparta in the fifth century BCE. The central message has stayed remarkably consistent across more than two thousand years: in dealings between states, power matters more than principles.

Realists build their entire analysis on a few core assumptions. First, the state is the principal actor in world politics. Other bodies like international organisations or individuals exist, but their power is limited. Second, the state acts as a unitary actor, speaking with one voice especially in times of war. Third, decision-makers are rational actors whose rational choices lead to the pursuit of national interest. Finally, states live in a condition of anarchy, meaning no one is in charge internationally. These four assumptions form the foundation on which the realist view of war is constructed.

Anarchy and the inevitability of conflict 🔗

The single most important concept in realist thought is anarchy. This does not mean chaos or lawlessness. In international relations, anarchy simply refers to the absence of a higher authority above sovereign states, a world without a global government that can enforce rules or guarantee anyone’s safety.

This structural condition changes everything. Inside a country, citizens can call the police or take disputes to court. Between countries, there is no equivalent. If one state attacks another, there is no international “911” to dial. Realists argue that this anarchic structure compels states to prioritise their own survival and pursue their interests in a competitive and often aggressive manner. Conflict and war become a constant threat because each state must, ultimately, ensure its own survival, sometimes at the expense of others.

This is why realists are sceptical that anarchy can ever truly be overcome. According to the realist perspective, states will never feel secure enough to surrender their sovereignty to a higher authority in some form of world government. Without that authority, the threat of war never fully disappears.

The security dilemma 🔗

One of the most powerful ideas that flows from anarchy is the security dilemma. In a self-help system where states cannot rely on anyone else for protection, each state tries to make itself safer. But when one state strengthens its military or forms an alliance to feel more secure, neighbouring states perceive this as a potential threat. They respond by building up their own capabilities. The result is a cycle of action and reaction that can lead to arms races and increased tensions even when no state actively seeks conflict.

This dynamic plays out in the real world all the time. When one country modernises its navy, neighbouring countries may feel compelled to enhance their own naval capabilities in response, even if the original move was purely defensive. The tragedy of the security dilemma is that the very steps states take to feel safe can make the entire region less stable.

Hans Morgenthau and the principles of classical realism 🔗

If realism has a founding father in the modern era, it is Hans J. Morgenthau. A German-born scholar who witnessed the rise of Hitler, Morgenthau understood firsthand how unchecked power could shape politics. His landmark 1948 book Politics Among Nations: The Struggle for Power and Peace laid out the foundations of what we now call classical realism.

Morgenthau argued that international politics is governed by objective laws rooted in human nature, and that the most important of these is the drive for power. He set out six principles of political realism, several of which are essential for understanding the realist view of war.

Politics is rooted in human nature 🔗

Morgenthau’s first principle holds that politics, like society in general, is governed by objective laws that have their roots in human nature. For classical realists, human beings are inherently driven by a desire for power. Because states are run by people, this same drive shapes how nations behave. War, in this view, is partly an expression of a permanent feature of the human condition.

National interest defined as power 🔗

The second and most famous principle is the idea of interest defined in terms of power. Morgenthau argued that this concept is the main signpost guiding realism through the landscape of international politics. Every nation, he claimed, conceptualises its national interests in terms of power and then acts to secure them through power. As one analysis of his work puts it, a national interest not backed by power exists only on paper and in imagination.

This is why realists place such heavy emphasis on military capability. For Morgenthau, the national interest is primarily concerned with the resources, especially military and economic capabilities, that determine the national power of the state. A nation that neglects its strength leaves itself vulnerable in a competitive world.

Separating morality from politics 🔗

Morgenthau also drew a sharp line between private morality and the moral demands of statecraft. He maintained that universal moral principles cannot be applied to the actions of states in the way they apply to individuals. A leader’s first responsibility is the survival of the nation, not abstract ethical ideals. This does not mean realists ignore morality entirely, but they insist that prudence, the careful weighing of consequences, is the supreme virtue in politics. A foreign policy driven by moral crusading, in the realist view, often leads to recklessness and disaster.

From classical realism to neo-realism 🔗

For decades, classical realism dominated the study of international relations. But by the late 1970s, a new variant emerged that would reshape the field. This was neo-realism, also called structural realism, developed primarily by the American political scientist Kenneth Waltz. Waltz was best known as the originator of the neorealist theory of international relations, which he set out most fully in his 1979 book Theory of International Politics.

The key difference between Morgenthau and Waltz lies in where they locate the cause of war. Classical realists like Morgenthau point to human nature, the inherent lust for power. Waltz found this explanation unsatisfying. If human nature is constant, he reasoned, it cannot explain why some periods see war and others see peace. Something else must be doing the work.

The structure of the international system 🔗

Waltz’s answer was the structure of the international system itself. He argued that the anarchic structure, combined with the distribution of power among states, explains recurring patterns of state behaviour far better than the personalities or motives of individual leaders. In his own framing, neorealism rejects the assumption that man’s innate lust for power constitutes a sufficient cause of war on its own. Instead, it reconceives the causal link between states and international outcomes by focusing on the system that contains them.

This shift from human agency to system structure is the defining move of neo-realism. The argument is that you could replace every leader in the world with a different person, and as long as the anarchic structure remained, states would still compete, balance against each other, and occasionally go to war. The pressures of the system shape behaviour regardless of who is in charge.

Survival, self-help, and the balance of power 🔗

For Waltz, survival is the minimum goal of every state. As he put it, only if survival is assured can states safely seek other goals such as profit, tranquillity, or greater power. Because there is no higher authority to provide protection, states operate in a self-help system. They must rely on their own resources to stay safe.

This leads to one of neo-realism’s central predictions: the balance of power. When one state or alliance becomes too powerful, others respond by building up their own strength or forming counter-alliances to restore equilibrium. Concentrations of power provoke balancing behaviour. This tendency, realists argue, is a recurring pattern across centuries and across very different types of governments, which is exactly why they believe structure matters more than ideology.

Offensive realism and the modern debate 🔗

Neo-realism itself later split into two camps. Defensive realists, following Waltz, argue that states seek only enough power to feel secure, since pushing for too much triggers balancing by others. Offensive realists, led by John Mearsheimer in his 2001 work The Tragedy of Great Power Politics, take a darker view.

Mearsheimer’s theory rests on five bedrock assumptions: the international system is anarchic, all great powers possess offensive military capabilities, states can never be certain of others’ intentions, survival is the primary goal, and states are rational actors. From these, he concludes that states will constantly seek to accumulate power, because the safest position in an uncertain world is to be the most powerful. The “tragedy” is that even states that only want security are forced into competition and conflict with one another. This pessimism is rejected by many defensive realists, who argue that endless power-seeking is self-defeating.

The philosophical roots of fear 🔗

Both classical and neo-realist arguments ultimately draw on a much older idea. The image of a world where each actor must fear every other actor echoes the seventeenth-century philosopher Thomas Hobbes and his description of a “state of nature” as a war of all against all. Realists adapt this Hobbesian logic to the international system: fear, uncertainty, and the pursuit of self-preservation push states toward conflict, not because they are necessarily evil, but because the absence of a common authority leaves them no other reliable option.

Why the realist view still matters 🔗

Realism has dominated international relations theory since the Second World War, and for good reason. It offers a parsimonious, hard-headed explanation for some of the most persistent features of world politics: arms races, shifting alliances, recurring great-power rivalry, and the stubborn refusal of war to disappear. Whether we look at competition in the Indo-Pacific, tensions along contested borders, or the steady growth of defence budgets across the globe, the realist lens helps explain why states behave as they do even when cooperation might seem more sensible.

Critics argue that realism places too much weight on power and conflict, underestimating the role of international institutions, economic interdependence, ideas, and the possibility of cooperation. These debates are far from settled. But understanding the realist view of war remains essential, because it forces us to confront an uncomfortable question about whether peace is the natural state of affairs or a fragile achievement that must be constantly defended.

What do you think? If war is truly rooted in the structure of an anarchic international system rather than in the choices of individual leaders, how much real power do diplomats and peace movements actually have to prevent it? And do you find the classical realist focus on human nature or the neo-realist focus on system structure more convincing as an explanation for why wars happen?

References

1. https://www.e-ir.info/2018/02/27/introducing-realism-in-international-relations-theory/
2. https://www.e-ir.info/2011/08/29/realist-and-constructivist-approaches-to-anarchy/
3. https://banotes.org/international-relations/kenneth-waltz-neorealism-structural-analysis-ir/
4. https://www.yourarticlelibrary.com/international-politics/morgenthaus-realist-theory-6-principles/48472
5. https://nationalinterest.org/feature/trump-can-learn-morgenthaus-6-principles-political-realism-19481
6. https://www.britannica.com/biography/Kenneth-N-Waltz
7. https://users.metu.edu.tr/utuba/Waltz.pdf
8. https://philopedia.org/thinkers/kenneth-neal-waltz/
9. https://en.wikipedia.org/wiki/The_Tragedy_of_Great_Power_Politics