When is war justified? What makes a just war? These are difficult questions to answer, but particularly so for Christians, followers of Jesus, who suffered violence without responding in kind. One philosopher-theologian who wrestled with these issues was Thomas Aquinas. Dr. Gregory Reichberg, research professor at the Peace Research Institute Oslo, explores this subject in his new book Thomas Aquinas on War and Peace (Cambridge University Press, 2017). Not only does this work do an excellent job in probing in an accessible yet deep way Aquinas understanding of just war, Reichberg both reveals aspects of Aquinas thought on war that are rarely examined, such as the connection between the cardinal virtue of fortitude and military service, and connects Aquinas and the just war tradition to contemporary debates about the waging of war. This book is highly recommended for anyone interested in this subject, and it has something to say both to people largely unfamiliar with it, as well as those who have studied the subject at length.