Sometimes you get a better result if you leave some of your cavalry or swords in the fort with your archers, if you can. This leaves a little reserve which can give a nasty shock and lower the enemy's morale even more, after it has dropped during the siege.
Experiment with the calculator to see what works best, but as stud says archers belong in the fort and not outside.
well,old tactic...2/3 units inside fort are archers and rest cavalry