Indeed it was the Mongols!!! Now just where and how they got elephants is beyond me....they just showed up with a very ´small but powerful jihad. When I went to attack it I noticed that despite me having a very heavy duty army with lots of powerful unit types the blue/red bar was way in their favor. I backed off to examen the stack and saw two elephants a decent general and a few other so so units. I brought in another stack that was just behind the city and attacked...needless to say it was still a bloody route...