...U.S. officials confirm that the terrorist group appears to have crossed a threshold with its use of unmanned aircraft. Two years after the Islamic State first used commercially purchased drones to conduct surveillance, the militants are showing a growing ambition to use the technology to kill enemies, U.S. officials and terrorism experts say.
The threat to troops is serious enough to prompt U.S. and Iraqi commanders to issue warnings to soldiers near the front lines. But a far bigger worry, U.S. officials say, is the potential for future attacks against civilians. Islamist militants have long discussed the possibility of using drones as remote-controlled missiles that can deliver explosives or even unconventional weapons such as deadly nerve agents. In recent weeks, the notion of terrorist drones has moved a step closer to reality, terrorism experts say....
