Battling them at bridges does NOT work, specially in the begining of their invasion when they attack with elephants :(
Also without the elephant they are too hard to hold at bridges cause they have to much missile and cavalry units

The best way for me was as same as with the Mongols ( If you assassinate every family member befor they take their first city, their armys will dissapear without becoming rebels :)

Although this metod of mine takes the most preparation and is not sure to succsed, since you have to complettgy cover a large territory with watchtowers to see whe they firts appear, and a LOTS of PROassassins, also you have to fight them of form obtainig the first city