Kenneth N. Waltz (born 1924, Ann Arbor, Michigan, U.S.—died May 12, 2013, New York, New York) was an American political scientist and educator best known as the originator of the neorealist (or structural realist) theory of international relations.

Waltz was drafted into the U.S. Army during World War II and served again in the Korean War. After graduating from Oberlin College (1948) with a degree in economics, he obtained a Ph.D. in political science from Columbia University (1957). He wrote his dissertation under the direction of William T.R. Fox, an important theorist of military policy who is remembered for having coined the term superpower. Waltz taught political science at Oberlin (1950–53), Columbia (1953–57), Swarthmore College (1957–66), Brandeis University (1966–71), and the University of California, Berkeley (1971–94), where he was eventually appointed Ford Professor of Political Science (later emeritus). In 1997 Waltz returned to Columbia University as an adjunct lecturer and senior research scholar at the Institute of War and Peace Studies.

Waltz’s doctoral thesis, which was published as Man, the State, and War: A Theoretical Analysis (1959), was a work of political theory (see political philosophy) examining the views of the great thinkers of Western political thought on the causes of war and peace. He is better known, however, as an international relations scholar. When Waltz entered graduate school, there was no discipline of international relations as such, though there had been empirical studies of foreign affairs. Waltz played a key role in the development of the field. His most influential work, Theory of International Politics (1979), a systematic account of the international balance of power, remained a canonical text in political science well into the 21st century.

According to Waltz, international politics is best understood by examining the structure of the international system as reflected in alliances and other cooperative arrangements between states. Waltz’s neorealist approach is part of political theory’s realist tradition in that it understands politics as the competitive interplay of self-interested actors. But it departs from classical realism (exemplified in the work of Hans Morgenthau) in its effort to provide a scientific and structural account of these power-based relations. The two main features of Waltz’s theory are the anarchic state of international relations and the distribution of power among states. The condition of anarchy refers to the absence of a higher authority to adjudicate international disputes. Simply put, world politics is anarchic because there is no world government. Second, world politics is characterized by an unequal distribution of power and by the capacity of the most powerful states to impose a world order concordant with their interests. According to Waltz, the key factor in international relations is the polarity of the system—that is, whether it is dominated by one, two, or many superpowers (unipolarity, bipolarity, and multipolarity, respectively). He considered the unipolar system that prevailed in world politics after the fall of the Soviet Union to be the most unstable and dangerous configuration, because it left one superpower (the United States) free to engage in foreign adventures.

In his later work, Waltz attempted to understand the impact of nuclear weapons on international politics. He emphasized their deterrent effect, contending that countries that have nuclear weapons coexist peacefully because of the abiding prospect of retaliation. On this basis, Waltz held that nuclear proliferation does not threaten, but on the contrary, buttresses world peace, provided that nuclear stocks are controlled by competent governments.

Although Waltz was most interested in the theoretical dimensions of international relations, he also held controversial positions on U.S. foreign policy. Because no checks and balances exist in world politics, he argued, great powers are almost certain to abuse their power, often against their own interests. Waltz noted that frequent U.S. military interventions abroad often resulted in burdensome commitments to stabilize and rebuild other countries. He opposed the Vietnam War and the U.S.-led Iraq War as misguided enterprises.

Waltz’s other scholarly works include Foreign Policy and Democratic Politics: The American and British Experience (1967), The Use of Force: International Politics and Foreign Policy (1971), The Spread of Nuclear Weapons: A Debate (1995; coauthored with Scott Douglas Sagan), and Realism and International Politics (2008). He served as president of the American Political Science Association in 1987–88 and was a member of the American Academy of Arts and Sciences.

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