Taking the case of the Columbia Country, which was annexed by the Black Forest People, it could only be considered an average province in the Kingdom of Alpha; however, once fully mobilized, it could also raise an army of between 100,000 and 200,000 troops.
The combat effectiveness aside, as long as people can be organized, that represents a non-negligible deterrent.
By using twenty percent elite calculation, such a troop deployment, as the defending side, would already be enough to dissuade the Black Forest Kingdom from any rash actions.
It's not a question of whether or not they can conquer the area, but rather that occupation would result in a loss greater than any gain. The consumption of a large amount of military power is secondary; the key issue is the difficulty of establishing rule after the war.
