As long as there 20% or greater in the hex. On this board that would include all of them. Personally, I don't like this board if I need to attack to take the town hexes. Even a small force can hold out the whole game. Towns reduce the bombardment effect and the hill gives the defender a +1 advantage in assaults, never mind the -2 and -1 for towns and height for direct fire. Which means even if you get some sort of positive column shift, your still shoot two columns down.