[6] That was interrupted to serve in the United States Army from 1944 to 1946 during World War II,[7] when he rose in rank from private to first lieutenant.

[7] During his PhD studies, Waltz was most interested in political theory, but gravitated towards international relations due to the academic job market and the pressure of his dissertation advisor.

[8] While preparing for his comprehensive exams, Waltz came up with the ideas that would ultimately become his dissertation and his 1959 book Man, the State and War.

[7] He then moved on to Brandeis University for a stint from 1966 to 1971, the last four years of which he held the Adlai E. Stevenson Professor of International Politics chair.

[7] In 1971, Waltz joined University of California, Berkeley, where he was appointed the Ford Professor of Political Science.

[7] He was a Fellow of the American Academy of Arts and Sciences[7] and served stints on the boards of editors of several scholarly journals[which?].

[10] Waltz's initial contribution to the field of international relations was his influential 1959 book, Man, the State, and War.

A prime example that Waltz referred to is Lenin's theory of imperialism, which posits that the main cause of war is rooted in the need for capitalist states to continue opening up new markets in order to perpetuate their economic system at home.

Today, a more familiar example in the Western world is the notion that nondemocratic states, because of their internal composition, start wars.

In that context, "anarchy" was defined not as a condition of chaos or disorder but one in which no sovereign body governs the interactions between autonomous nation-states.

In other words, in domestic society, citizens can theoretically rely on law enforcement agencies to protect their persons and property, but if a state is invaded and calls "9-1-1," it cannot be sure that anyone will answer.

[citation needed] Waltz's key contribution to the realm of political science is in the creation of neorealism (or structural realism, as he calls it), a theory of international relations that posits that the interaction of sovereign states can be explained by the pressures exerted on them by the anarchic structure of the international system, which limits and constrains their choices.

[citation needed] Waltz emphasizes repeatedly in the book and elsewhere that he is not creating a theory of foreign policy, which aims to explain the behavior or actions of a particular state at a specific time or throughout a period.

The anarchy of international politics, with its lack of a central enforcer, means that states must act in a way that ensures their security above all, or they otherwise risk falling behind.

He wrote that this international anarchy is a fundamental fact of political life faced by democracies and dictatorships alike.

[17] The theory explains only general principles of behavior that govern relations between states in an anarchic international system, rather than specific actions.

In Theory of International Politics (1979:6) Waltz suggested that explanation, rather than prediction, is expected from a good social science theory since social scientists cannot run the controlled experiments that give the natural sciences so much predictive power.

As a teacher, Waltz trained numerous prominent international relations scholars, including Stephen Walt, Barry Posen, Stephen Van Evera, Bob Powell, Avery Goldstein, Christopher Layne, Benny Miller, Karen Adams, Shibley Telhami, James Fearon, William Rose, Robert Gallucci, and Andrew Hanami.

[19][20] Columbia University colleague Robert Jervis has said of Waltz, "Almost everything he has written challenges the consensus that prevailed at the time"[4] and "Even when you disagree, he moves your thinking ahead.

"[1] Leslie H. Gelb has considered Waltz one of the "giants" who helped define the field of international relations as an academic discipline.