The intense debate over US targeted drone strikes outside war zones has been limited by the failure to review and assess a considerable body of quantitative research and qualitative material on the impacts of such strikes on terrorist groups and civilians. This book fills an important gap in the literature by conducting a careful and rigorous review of such evidence. It argues that decisions about the use of targeted strikes as a counterterrorism instrument, as well as legal and ethical evaluations of such use, must be informed by our best understanding of the insights that empirical evidence can provide on the effectiveness of strikes and the costs they impose on populations where they occur.