Leaders don’t get much attention from international relations scholars, who tend to favor abstract models and structural theories that discount the personalities or experiences of decision-makers. This important book brings state leaders back into debates about war and peace. Drawing on insights from historians and psychologists, the authors find interesting patterns in the attitudes of leaders toward risk and the use of force. The book’s major contribution is its massive data set, which includes 2,400 leaders from around the world over the last century. The authors argue that prior combat experience seems to dampen leaders’ enthusiasm for war. However, those leaders who served in the military but had no direct experience of combat have been among the most likely to initiate or escalate military conflict. Gender does not seem to matter, but age does: in democracies, young leaders are less likely to use military force than older ones—perhaps, the authors speculate, because older leaders fear they have less time to make their mark. The book also documents a positive correlation between having a troubled childhood and engaging in risk-prone behavior as an adult political leader.