Originally Posted by
dvk901
Actually, the AI is somewhat limited as far as what it can 'see'. It's hard to say 'definitively' what and how far their vision is, but years of testing by others and by myself have shown that the AI's vision is 'flat'...in otherwords, they are standing on the ground (not overseeing the map as the player does) and can see up to either a hardcoded distance, or up to a point where their vision is obstructed by mountains and forests. This was one reason that map makers had to be careful how the map was constructed terrain-wise, and movement points had to be adjusted to a setting that would prevent the AI from losing sight of its own armies...which would then get 'stuck'.
So, at a certain distance from a faction you border, you could have 20 stacks sitting there waiting and the AI wouldn't know it because it can't see them.