Battle Line
Can you claim a flag against an empty opposing side with a completed 8-9-10 Wedge of one colour?
The Flags and Formations sections make a Wedge the highest formation and the tie rule decides the flag, so the claim is proven from the table.
Yes. Once the 8-9-10 Wedge of one colour is on your side, the opponent's best possible formation can only tie it, and a tie goes to the player who completed first, so you may claim it on your turn. Unplayed Tactics cards are ignored. The claim does not work if Fog or Mud is already on that flag, because those change how the flag is decided.