Don't forget that drones are evolving very fast and their potential is frightening. What about swarm of unmanned AI and computer vision capable drones spreaded across fields and forests waiting for their prey? You can make antipersonnel drones much smaller as you don't need even to kill the enemy - just to wound. You can place a big batteries across that zones so drones could go recharge theirselves and continue serving. Eventually you can just drop thousands of such killers above the territory or even some city and they will kill every human they find. Ok, then we can make unmanned drone hunters and human killer bots will start to enhance their defense capabilities. That will start another round in evolution where humans on the battlefield are just spectators. Or prey if they unlucky.