Battle Territory bonus can be found on a cell marked with a gift box icon on the world map. It appears twice in every zone and awards an X amount of max. Trimps. The default amount of max. Trimps awarded per gift box is 5, however, that amount can be increased with the Trumps perk.
The bonus to max. Trimps from the Trumps perk to battle territories already unlocked by the player is persistent, which means that it stays even if the player uses a respec. Because it is persistent, it is possible to put all your points from your previous run into Trumps, then respec at a higher zone putting more points into other perks while keeping the additional population.
Battle Territory bonus is also affected by the Carpentry perk.