How to tame autonomous weapons

FOR THOUSANDS of years, weapons went where humans thrust, threw or propelled them. In the past century, they have grown cleverer: more able to duck and weave to their targets; more able to select which of many ships, tanks or aircraft to strike; and more able to wait for the right target to turn up. Increasingly, such weapons can be let loose on the battlefield with little or no supervision by humans.The world has not entered the age of the killer robot, at least not yet. Today’s autonomous weapons are mostly static systems to shoot down incoming threats in self-defence, or missiles fired into narrowly defined areas. Almost all still have humans “in the loop” (eg, remotely pulling the trigger for a drone strike) or “on the loop” (ie, able to oversee and countermand an action). But tomorrow’s weapons will be able to travel farther from their human operators, move from one place to another and attack a wider range of targets with humans “out of the loop” (see ). Will they make war even more horrible? Will they threaten civilisation itself? It is time for states to think harder about how to control them.