In reply to the previous post, no HA's (or any unit that can withdraw for that matter) can't withdraw while they are defendeing. When others say that they are excellent defenders, they are referring to the NC's ability to do extra damage to melee and catapults, the primary medium of any invasion force. Even spears don't offer that good a defence against NC's, and in some cases, it's 50/50. Also, the NC's high withdrawal chance and 2 movement points allow it to attack a stack in friendly lands and then move a turn away from the stack, preventing any sort of counterattacks. Hope that clears up any misconceptions.