War is traditionally conceived as armed conflict, but it is more than that: it is a political construct of who fights and who dies, who possesses power, and who profits. Kenneth B. Moss provides an insightful portrayal of this through a parsing of the phenomenon of “private war,” which is delineated as a distinctive practice with the consolidation of states’ authority in the seventeenth century. Whereas “public war” derives from the politics and policies of governments to use force, “private war” reflects a murkier set of actors and drivers that operate independently of state authority. However, in Moss’s framing, “public” and “private” are not exclusive categories but “spheres” that can overlap—such as “privateering,” which authorizes private actors, usually with commercial interests, to operate at the behest of states. His study illuminates the when, how, and why of different configurations.

Although Moss touches on the use of mercenaries in ancient times through the Middle Ages, he is primarily concerned with the United States— indeed, the title of Moss’s book is a reference to the exclusive power of Congress to grant private actors licenses to use force: marque, permitting an inflicting of injury on another, and reprisal, sanct