After reading about the First Crusade, I decided to make a map on it. I've experimented greatly with this, and have found you can win easily, or lose terribly, depending on how you go about it.
To win, you must kill all enemy defenders, before reinforcements can arrive and smash your poor army to pieces.
The map is nearly 100% accurate, with a little creative rendering the the scenery to try and add some spice to it.