The Biden Administration, in one of its first consequential foreign policy decisions, announced that it would undertake a comprehensive review of the United States drone program. Officials promised that this review would consider all available evidence. In this Article, show that the U.S. drone program violates international law because of the ways it terrorizes civilian populations. U.S. officials from both parties have argued that drones are an effective part of the U.S. counterterrorism strategy. But effectiveness is not the legal standard. The law requires that the program not unduly harm civilians. For as long as the U.S. has been using drones, communities in targeted countries have contended that the U.S. kills innocent civilians. The U.S. has typically minimized these claims, even as it has acknowledged some of the deaths. Until recently, this was the state of the argument: the U.S. argued that the drone program was effective, with minimal effects on civilians, and others argued that it caused undue harm to innocent civilians. Neither side found the evidence cited by the other side credible or gave much credence to the other side’s arguments. There is now a growing body of empirical evidence that shows how the U.S. drone program terrorizes civilians in ways that violate the law. Drawing on research from several disciplines, I show the ways the drone program affects the targeted population, civilian and militants alike. The evidence shows that even if drone strikes kill terrorist leaders—strikes the U.S. would consider successful—militants shift their attacks from military targets to civilians. The evidence also shows that the main reason militant violence goes down is not the strikes themselves but the monitoring and surveillance apparatus associated with the drone program. Areas in which the U.S. maintains an active drone strike program are typically under persistent surveillance and monitoring. Communications are monitored, movements are tracked by surveillance drones, and intelligence-gathering operations are ongoing. Civilians are terrorized by these practices. Taken together, this evidence shows that U.S. operations violate international law because they are indiscriminate: they affects civilians and militants alike, with little effort made to reduce civilian harms.