The HQ, when activated, allows units in the same hexagon as the HQ and the ones next to the HQ hexagon to launch offensives.
ok, when the HQ is present, adjacent armies can attck. But how do armies go onto the offense, eg.start heading towards Russia? Do you bring the HQ with you? Do you build more? Or is there some type of supply line? I actually find it a bit odd that you have to have an HQ by you to launch an offensive.
Now, I could see that having an HQ present increases morale, fatigue,supply, etc,etc,etc. But to need an HQ present to launch attacks seem a bit unrealistic.