They would win urban warfare fast, but not just that. After killing everyone in the city there could be other robots that clean the bodies away neatly in body bags (to avoid more blood stains), and even robots that clean blood stains, remove food items from fridges and shut down devices and lights to preserve energy (also, fireman robots could put off fires). All that could happen without us. Soldiers would not have to kill women and children, robots could simply "remove" them.
Robots could also remove personal items from homes and steal valuable items. Then the city could be just left waiting for new settlers.
How great is that? I can't wait to see when robot technology gets into that level.