I knew that, if you don't storm a castle, when it falls it gets downgraded one level (castle to keep etc)but I only just noticed that if you invade a province and the enemy retreats out of the province without a fight, (ie right out, not to the castle), the same thing happens? I was left with just a fort, and an eight year wait to rebuild the keep that was there before.

Why? After a long seige I can just about see the castke will be a it bashed up, but how come it gets damaged when the enemy has just legged it?

Any ideas on how this can be avoided? The defending army was quite small, and the attacking army pretty big, but the enemy had an enormous stack in an adjacent province to the one I was attacking and if I had slimmed my army down they would have sent in masses of reinforcements.

BTW, is it just me or is the fact that the AI gets to move all its armies after you have made all your moves one of the worst bits of the strategy game?