The game's AI is the most simplistic I've seen in any game. The units check for a target, take the most direct route and attack it. Sure this sounds all well and good, but when defenses are involved, this becomes a burden and often units will attack higher level walls even though a lower level wall is directly next to it. Units will even attack different walls when standing side by side. They also attack walls for 40 seconds when they could have walked around them in 10 or less.