Fully autonomous weapons would also cloud accountability in war. Without a human pulling the trigger, it's not clear who would be responsible when such a weapon kills or injures a civilian, as is bound to happen. A commander is legally responsible for subordinates' actions only if he or she fails to prevent or punish a foreseeable war crime. Since fully autonomous weapons would be, by definition, out of the control of their operators, it's hard to see how the deploying commander could be held responsible. Meanwhile, the programmer and manufacturer would escape liability unless they intentionally designed or produced a flawed robot. This accountability gap would undercut the ability to deter violence against civilians and would also impede civilians' ability to seek recourse for wrongs suffered.
Despite these humanitarian concerns, military policy documents, especially in the United States, reflect the move toward increasing autonomy of weapons systems. U.S. Department of Defense roadmaps for development in ground, air, and underwater systems all discuss full autonomy. According to a 2011 DOD roadmap for ground systems, for example, "There is an ongoing push to increase [unmanned ground vehicle] autonomy, with a current goal of ‘supervised autonomy,' but with an ultimate goal of full autonomy." Other countries, including China, Germany, Israel, Russia, South Korea, and the United Kingdom, have also devoted attention and money to autonomous weapons.
The fully autonomous sentry robot and aircraft alluded to above are in fact based on real weapons systems. South Korea has deployed the SGR-1 sentry robot along the Demilitarized Zone with North Korea, and the United States is testing the X-47B aircraft, which is designed for combat. Both currently require human oversight, but they are paving the way to full autonomy. Militaries want fully autonomous weapons because they would reduce the need for manpower, which is expensive and increasingly hard to come by. Such weapons would also keep soldiers out of the line of fire and expedite response times. These are understandable objectives, but the cost for civilians would be too great.
Taking action against killer robots is a matter of urgency and humanity. Technology is alluring, and the more countries invest in it, the harder it is to persuade them to surrender it. But technology can also be dangerous. Fully autonomous weapons would lack human judgment and compassion, two of the most important safeguards for civilians in war. To preserve these safeguards, governments should ban fully autonomous weapons nationally and internationally. And they should do so now.