Many times I've seen AI Armies/Corps stop and lay siege to a town with only a wounded/locked leader or a supply wagon/small force in the city or town!
IMHO this should be changed, looked at or addressed.
There must be some way for the AI to determine if there are no troops or very few troops in a town. If a Leader is present then it is either killed/wounded or relocated. If only a small force is present , then a direct assault should be conducted.
Mind you In the campaign game the wounded leaders wont be much of an issue but I have seen it happen. As for a single Militia (without Artillery and low intrenchment) against a sizable corps, I figure it would capitulate in a day.
Bigus