Battle Line
Can cards in your hand, or unplayed Tactics cards, be used to prove a flag cannot be beaten?
The Flags section says the claimant may use only open information and that unplayed Tactics cards cannot prevent a claim.
No. A claim is proven only from the open information on the table. Your own hand and unplayed Tactics cards are ignored. Tactics cards already in play still count, because they change the formations.