This book discusses the moral and legal issues relating to military drones, focusing on how these machines should be judged according to the principles of just war theory. The author analyses existing drones, like the Predator and Reaper, but also evaluates the many types of drones in development. The book presents drones as not only morally justifiable but having the potential to improve compliance with the principles of just war and international law. Realizing this potential would depend on developing a sound regulatory framework, which the book helps to develop by considering what steps governments and military forces should take to promote ethical drone use. It also critically evaluates the arguments against drones to show which should be abandoned and which raise valid concerns that can inform regulations.