"Obama has killed more people with drones than died on 9/11. Many of those killed were civilians, and only a tiny percentage of the dead were al-Qaeda or Taliban leaders. Obama's targeted killings off the battlefield are not only illegal and immoral; they also make us less safe due to the blowback from those who have lost family and friends. There was not much opposition to these killings among the American people." http://www.truth-out.org/news/item/...drone-warfare-illegal-immoral-and-ineffective
I think you'd have to go back to the days of uniformed troops meeting each other face to face in rank and file to find a form of warfare that kills fewer civilians per enemy combatant than drone warfare does.