Question on combat %'s from different OOB

[Disgruntled Veteran]

So I've been wondering this for a bit and the manual is clear..but not fully clear on how this works.

What I'm talking about is the % penalty you pay when a unit from a different OOB takes part in a battle. Is the % penalty applied just to the supporting unit or does it affect the entire combat force. For instance:

XVIII Corps with 3 defending divisions gets attacked and it is the primary combatant. Now lets add a reserve regiment from a unit thats adjacent but in a different AG. So lets say the penalty is 20% (I don't remember exactly what it is)does that 20% count against just the reserve regiment or the entire force? If its the entire force it often will hurt the battle more than it would help. This is crucial when planning your defense.

The manual makes it sound like it affects the entire force. I hope that's not the case. Anyone know for sure?

[cpt flam]

from what I have seen
the "original" corp will be full strength
others will be down from 6 to 30 per cent

[gingerbread]

The combat result screen says it all, the penalties applied are listed for each command. The 'Comm HQ' is also stated and units in that command does not have penalties.