when did sister corp units reserve activate for a battle when they have no units involved in the basic battle.
Here 2 panzer DIVISIONS (no less), activate.

Moderators: Joel Billings, Sabre21
The command organisation plays an important role in determining any reserves committed to a battle. The lower the Command Battle Modifier (15.6.3.4), the higher the chance the unit will be committed from the reserve (especially those units with a Command Battle Modifier below -10%). This means units attached to the same HQ as battle have a better chance of being committed than those attached a higher HQ. There’s also a better chance of motorized units being committed as you would expect.