Rome 2 Tips and un-/under-documented features

[Slaists]

I thought I saw the answer to this previously but I cannot find it. How do I force the army to stay in a formation without creating one large group? I want to be able to have in effect sub groups (eg right center and left) that move in a coordinated fashion. I think this has always been possible but I never learned how.

@Seyavash

1. Arrange your army the way you want it.
2. Select all (CTRL + A would do it)
3. In the field (not on unit cards), left click-hold on one unit in that army (while everybody is selected)
4. while holding down the left mouse button, drag the cursor to where you want your army to go; you will see a ghost of your army in the formation you selected moving there
5. upon releasing the cursor, the army will move to the target place and arrange themselves in the original formation
6. if you pres CTRL while doing #4, you'll be able to change the rotation of the army
7. while your army is marching (looking all messy) you can select everyone again (not waiting for them to stop) and give them a new location; they will still remember their original formation from step 1.