In my most recent campaign they decided to stand near Yerevan after I had just captured it,so I evacuated the city and left them to it.About 50-60 turms later 16 full mongol stacks turn up,bypass all the defended cities and lay siege my my city of antioch.What you do when they stand still and do nothing,as I'm pretty sure that they stood around long enough that the reinforcement waves that come later,added to their army,I didn't feel like taking that many stacks on in a field battle..