I had the exact same problem but with the Jerusalem I had that an Cairo and Gaza the mongals kicked me out of Damascus then the Damd Timurids turned up they kicked me out of all but Gaza I had a massive assult on Jerusalem and got my butt kicked I had a stack of mounted and dismounted Knights and Cannon they had a few elephants and oooch I gave the region up but not before a battle in the open which I would only do where I had the higher ground and bombarded them.