I had this funny experience. I was moving my main hero (but with a small army) past an enemy town with a hero and an army. I saw that his army was about three times larger than mine. I thought I needed to get out of there quickly. The AI was sitting in the castle. I took all of his mines. The AI just sat there. I ran around his territory back and forth, collecting resources. It still just sat there. I got tired of it and moved to another part of the map. The AI just sat there and didn't even try to retake the mines. I wondered for a long time, is it too embarrassing for it to take back what's rightfully theirs after someone else has taken it? :)