The AI does cheat of course, just as it did in MTW and STW. Just as it does in most strat games (Civilisation anyone?). It is programmed to because this is the only way it can provide a challenge to the player. It is just a pity that when you do see a large AI army it is always a bizarre mix of units. After getting hit by waves of pitifully small armies of hastati it was good to see a ful stack oming at me. Shame it consisted entirely of velites, but never mind.