It was a gameplay decision. Remember orders are sent from the Army HQ (which would be the human player) to the next level down HQ and then to the actual unit HQ. Each step of the way delay, based on the distance that the courier has to travel and the Leadership Value of the HQs is added.
Fore more information about couriers in
General Staff click on this link:
http://general-staff.com/tag/couriers/I've attached a screen shot of my original
UMS II: Nations at War which had, technically, four levels of command) but really just three (you couldn't 'order' Montgomery or move him):

What I wanted to avoid was turning this into a massive chain of command game where it took hours to send orders from the Army HQ to the individual units. It was my decision so feel free to yell at me.
