Walkthroughs for custom maps.

Suddenly realized that I can't clearly explain when the computer-controlled opponent leaves the castle and when it doesn't, and consequently, when it breaks through using a teleport/clone, and when it only breaks through using a force field. Typical situation: the computer-controlled opponent has dragons/phoenixes, archers with no shots/blinded/forgetful, and no mana left, and no archers of its own. What will the enemy flying units do?