I really appreciate all of your responses. It turns out that it wasn't nearly the problem I thought it was going to be. You were right - I have pushed the Almohads back to Tunisia and I've only seen 4-5 units of AUM. (I'm playing on hard difficulty). Most of the time I've got the rest of the Army routing by the time the AUM becomes a factor and they run as soon as the javelins start to fly.

I appreciate all of your help everyone