Games with dragons, spaceships, and bears aren’t wargames. Call them conquest games or strategy games or crap but they aren’t wargames.
But doesn't make conquering it a French major fortress?
Based upon 19.1 bullet 1 I’d say no the fortresses you conquer can’t be used to bring pieces on the board. The cited bullet makes a specific exception to the rule, which implies you normally can’t. I’m sure the designer will weigh in on this question.