In the past, when wars in the West were fought in a heroic effort to achieve grand purposes, governments and citizens were apparently willing to accept large numbers of casualties. Today, by contrast, there tends to be a preference for ‘post-heroic’ forms of warfare characterized by reduced physical risk to the wielders of violence and possibly to the victims too. New military technologies afford greater capacity for stand-off and accuracy in the use of force, and the possibilities of airpower are especially attractive. Such is the background for this chapter's discussion of some key technical aspects of armed drones, and of how and why the United States has come to use this technology. Such use (including by other countries) is likely to increase and develop in the future, and this is an important reason for decision-making on this issue to be guided by ethical principles.