In 1948, Hans J. Morgenthau wrote his classic text, Politics Among Nations: The Struggle for Power and Peace, that was largely responsible for establishing realism as the prevailing theory in the field of International Relations (IR). In 1979, Kenneth N. Waltz wrote an immensely influential book, Theory of International Politics, that resulted in a new structural version of realism – neorealism – becoming the dominant theory in IR. John J. Mearsheimer, who is the R. Wendell Harrison Distinguished Service Professor of Political Science at the University of Chicago, has written a profoundly important book that rightfully deserves a prominent place along with Morgenthau and Waltz in the canon of realist thought about international politics. Mearsheimer's clearly written book puts forth a new structural theory of realism that he terms offensive realism. This version of realism argues that the observable patterns of behaviour among all of the great powers throughout history, most notably their ubiquitous power-seeking, can be explained by the fact that they exist in a condition of anarchy in which there is no higher source of authority above them. While sharing many of the same basic assumptions with neorealism, offensive realism, as elucidated by Mearsheimer, provides a fundamentally different account of the essential dynamics of international politics than that which Waltz and his students have been offering for the last twenty years or so.