The United States increasingly relies on unmanned aerial vehicles, better known as drones, to target insurgent and terrorist groups around the world. Drones have a number of advantages that could fundamentally alter how the United States engages in counterinsurgency and counterterrorism operations. Unmanned aerial systems comprise a rapidly growing portion of the military budget, and have been a long-term interest of Congress. At times, Congress has encouraged the development of such systems; in other instances, it has attempted to rein in or better organize the Department of Defense’s efforts. This book discusses the effectiveness of drone strikes in counterinsurgency and counterterrorism campaigns; and focuses on the military uses of UAS.