Gat addresses two of the biggest questions in international relations: Why do wars still occur? And is the world becoming more peaceful? His answer to the second question is close to the one offered by the cognitive scientist Steven Pinker, whose optimistic thesis holds that violence has declined over the course of human history and will continue to do so. Gat, however, does not promise that the trend will continue—a wise move, in light of recent events. After opening chapters on prehistoric war, which Gat describes as vicious and ubiquitous, his book goes on to argue for the importance of modernization in dampening violent urges, which it does by making peace seem so much more attractive. With the rise of U.S. power, the modernization process took a distinctly liberal turn and served as the basis for optimistic post–Cold War visions of a peaceful future. That optimism has been dented. Gat is less than confident that benign trends will continue, noting the challenge posed by more authoritarian forms of modernization, exemplified by China, and the risks to peace from societies that have turned against modernization altogether, especially in the Middle East.