Kenneth N. Waltz (1924–2013) was a preeminent scholar of international relations. He was Ford Professor Emeritus at the University of California, Berkeley, and was senior research scholar at the Institute of War and Peace Studies at Columbia University, where he began his academic career. His books include Theory of International Politics (1979). Stephen M. Walt is Robert and Renée Belfer Professor of International Affairs at Harvard University’s John F. Kennedy School of Government.