Joshua Byun is assistant professor of security studies in the Edmund A. Walsh School of Foreign Service, Georgetown University, and author of The Adversary's Veto: Rival Powers, Alliance Politics, and the Limits of Grand Strategy. John J. Mearsheimer is the R. Wendell Harrison Distinguished Service Professor of Political Science at the University of Chicago. He is author of The Tragedy of Great Power Politics and The Great Delusion: Liberal Dreams and International Realities, and coauthor of How States Think: The Rationality of Foreign Policy.