The first option allows to choose the mode :
* you are the CinC of each side (M1)
* you are the Cinc of one side and Great Tactical AI controls the other side (M2)
* GT AI controls the 2 sides.
At the beginning of battle, the GT AI builds a tactical plan for the side managed by itself.
(take a look at the French text in the blog :
http://www.jm-mathe.fr/)
So, the idea in order to keep the initial position is:
a) choose the mode (M1) where you are the CinC of each side
b) send orders for 2 sides
c) launch the battle
d) in F7, modify the option M2 to keep the control of only one army. GT AI tries to do the best to control the other one.
Clear?
Enjoy
JMM