Kenneth Waltz

Kenneth Waltz was an American political scientist who founded neorealism, also called structural realism, the most influential school of thought in international relations in the late twentieth century. Waltz argued that the structure of the international system, not the character of individual states or the people who lead them, explains why countries compete and go to war. Theory of International Politics, which he published in 1979, went on to become the single most widely used book in American graduate courses on international relations. Waltz taught at Columbia University, Swarthmore College, Brandeis University, and the University of California, Berkeley over a career that lasted more than fifty years. He was born in 1924 in Ann Arbor, Michigan, and died in 2013 in New York.

How Kenneth Waltz built a new theory of war

Waltz grew up in Ann Arbor and entered Oberlin College in Ohio as a mathematics major. World War II interrupted his studies. He served in the United States Army from 1944 to 1946, rose from private to first lieutenant, and was stationed in Japan during the American occupation. He returned to Oberlin, switched to economics, graduated in 1948, and earned his doctorate at Columbia University in 1954.

Waltz's first book, Man, the State, and War (1959), organized thinking about war into three levels of explanation, which he called "images." The first pointed to human nature, the claim that aggression is built into people. The second pointed to what goes on inside states, the argument that certain types of government are prone to fighting. Waltz focused on the third: wars keep recurring because sovereign states operate without any higher authority above them. Each state must provide for its own security, and none can fully trust any other. The first two levels of explanation account for why specific wars start, but only Waltz's third image accounts for why war as a general phenomenon never goes away.

Twenty years later, Waltz expanded that insight into a full theory. Theory of International Politics (1979) argued that the structure of the international system, not what happens inside any individual state, determines the pattern of world politics. Classical realists like Hans Morgenthau had explained power politics as a product of human nature, the idea that people and the states they run are inherently competitive. Waltz moved the explanation to the system itself. He compared states to companies competing in an open market: regardless of their values, ideology, or leadership, the pressure of competition pushes them all toward the same self-protective behavior. A state that fails to balance against threats risks the same fate as a company that ignores its competitors.

What is neorealism?

Neorealism, or structural realism, is the theory that the anarchic structure of the international system is the main driver of conflict among states. "Anarchy" here does not mean chaos. It means there is no authority above sovereign states that can enforce agreements, settle disputes, or protect anyone. States must rely on themselves.

Waltz argued that this single structural fact explains why states across different centuries, cultures, and political systems end up behaving in similar ways. Democracies and dictatorships alike balance against threats, build militaries, and form alliances, because the system gives them no safe alternative. A state's leaders and ideology matter less than the position it occupies in the structure.

One of Waltz's most debated conclusions was that a bipolar world, with two great powers, produces fewer wars than a system with several competing powers. When only two great powers exist, the two watch each other carefully, the chances of misjudging the other's intentions drop, and no web of shifting alliances can pull either into someone else's conflict. The argument offered an explanation for why the Cold War, for all its danger, never became a direct war between the United States and the Soviet Union.

Kenneth Waltz on nuclear weapons

Waltz applied his structural logic to nuclear weapons and reached a conclusion that unsettled even his admirers. If the threat of a devastating counterstrike makes great powers careful, then nuclear arsenals promote stability. In 1981 he published "More May Be Better," an essay arguing that the controlled spread of nuclear weapons could calm dangerous rivalries by making war too costly for any side to start.

Stanford political scientist Scott Sagan took the opposite view. Sagan argued that new nuclear states lack the organizational controls to manage their weapons safely, and that the risk of accidents or unauthorized use rises with every new arsenal. The two published their arguments side by side in a book, The Spread of Nuclear Weapons, which became a standard text in security courses. Waltz maintained that new nuclear states grow cautious rather than reckless, because the consequences of miscalculation are too severe.

In 2012, at 88, Waltz published his most controversial piece, an article in Foreign Affairs called "Why Iran Should Get the Bomb." Waltz argued that an Iranian nuclear weapon would stabilize the Middle East by balancing Israel's existing arsenal. Critics found the argument alarming. Waltz considered it consistent with his theory: if deterrence works between the United States and the Soviet Union, or between India and Pakistan, there is no structural reason it should fail between Israel and Iran. He died the following May, in 2013.

Waltz's framework remains the starting point for most academic debates about why states compete, form alliances, and go to war.