Spoiler Alert, click show to read: 


Note that it is vulnerable to missile fire, so heavy cavalry is a must. Especially when dealing with onagers. thats why I use two general units, as they can take on a regular cavalry unit fairly quickly, and can then procedd to stomp on the enemy missiles. It is also virtually impenetrable to enemy units, but, just in case, it is good to have backup units. I usually take 15 phalanx, 2 archer, 1 onager, and 2 cavalry, but I grabbed to many this way and my phalanx had no supporting units. I usually have 1 or 2 units waiting within the circle for backup, and they patch when neccessary. Note that the onager is just for fun, and it does cause the enemy to lose morale and men. Please be careful when firing downhill, as the men in front of them are likely to take any misfored shots. If you do not win the battle, you will at least make sure that they lose alot of their men. More men than you lose, at any rate.

For the defense of a city:
Spoiler Alert, click show to read: 






Self Explanitory, pretty much. Strong defense on the walls they will attack, and if that fails, a decent defence in the center. Works pretty much all of the time.


(I copied my post from tactics thread)