Armed unmanned aerial vehicles-combat drones-have fundamentally altered the ways the United States conducts military operations aimed at countering insurgent and terrorist organizations. Drone technology is on track to becoming an increasingly important part of the country's arsenal, as numerous unmanned systems are in development and will likely enter service in the future. The increasingly frequent use of drones raises profound questions about the nature and morality of warfare involving asymmetrical risks between opposing belligerents. Concerned citizens, academics, journalists, nongovernmental organizations, and policymakers have raised questions about the ethical consequences of drones and issued calls for their military use to be strictly regulated. This level of concern is evidence that the future of drone warfare not only hinges on technical innovations, but also on careful analysis of the moral and political dimensions of war. Regardless of whether drones are effective weapons...