Ok on campaign #4 as Rohan trying to finish off Isengard's last army Mordor starts seiging one of my eastern towns. I send a general and 3 Eodred horse archers to try and save the town or get them to back off while more troops come up. Instead the stack of 6 units attacks and I laugh maniacally. My plan to empty the quivers of my horse archers then withdraw. Only the withdraw button for my units is greyed out. So why couldn't I withdraw? Did having the HA's in loose formation have anything to do with it? Thanks.