Focusing on 45 military leaders from four continents and 13 countries, spread across four centuries, this study paints, for the first time, a collective, comparative portrait of high-ranking military officers. The authors develop an interactional theory of military leaders, stressing the interplay between sociodemographic variables, psychological dynamics, and situational factors. They examine age and birthplace, socioeconomic status, family life, ethnicity and religion, education and occupation, activities and experiences, and ideologies and attitudes. They find military leaders to be a remarkably coherent and homogeneous group of men propelled toward the military by a combination of nationalism, imperialism, relative deprivation, love deprivation, marginality, and vanity.