Will try to defend as often as possible. Even when on the attack will try to leave a mini-army in a good defensive position ie: 2-3 missle, 2-3 cav/inf on a nice lil hill or the like where they can quickly be brought to bear. Also this gives you the chance to feign attack and withdraw through the range of this force and then engage with them.

My goal when attacking or defending is to bring every available form of attack to the battle.I wont engage in melee at all if possible until all arrows/bullets are gone. This may be overkill but an arrow/bullet is cheaper than a soldier. Also I find the idea of missle units being engaged and dying while they still have ammo entirely repulsive. Far better to run em out of ammo then lose them in melee no? Same goes for HA when I happen to use em.

Since the AI seems to LOVE attacking even when they are the defender,Ill happily oblige that deathwish.