[Lingchih]

Well, I've been playing with Elephants recently, and and I don't seem to have any problem getting them to attack rear. They do occasionally break off and attack the front army, but if I get their morale up, they do seem to usually go all the way to the commanders. A couple of sermon of courages will get their morale up to 12.

Granted, this means you need a strong force up front, so the elephants don't see any need to attack the frontmost army.