Okay, I have seen how the AI handles reenforcements and there is no way I want it doing so. (Attack the spearmen head on with the General's heavy Cav while the Principes throw their javs.)

I read in one of the faq's that I should be able to control them myself if there are a total of less than 20 units. There is a icon next to them on the initial screen after you initiate the battle that says next to it that the AI will control them. However, I cannot toggle it. I only have 9 total units, 4 in a beseiged city and 4 outside supporting. Do I have to change a game setting somewhere to allow me to toggle this?