Taken from tactics_manual.doc included in the docs folder:
A Commander has two features: Commander Radius and Commander Level. Radius shows the distance his commands work; Level defines effectiveness of his orders.
The units inside the Radius never panic, even under a heavy fire, and they never surrender or leave their positions, even if the enemy gets closer or their weapons got broken.
If a Commander got wounded, his Radius and Level decrease. To see Radius and level, use the [ \ ] key.
In tactical mode, the [ \ ] key is mapped to "Show order list and current targets" button; the 'o' button in the lower left button block.
The button has three states: (1) off, (2) show pulsing green lines, and (3) show orders and targets.
I think the pulsing green lines in state (2) are the command radii.
I used to think of them as communication links and that they only related to the speed at which orders are transmitted. But if they show the command radius then the quote from the manual suggests any unit connected to a command unit by a pulsing green line will never panic, surrender, or leave their positions. Is this true? It doesn't seem to fit with my game experience, but I've not focused on this too much before.
I have some questions of my own about the Command Level button, but I'll ask them in a separate thread.