I also remember Arma 2 having a scenario where you played as a Chernarusian rebel or something and had to fight off a Russian offensive and you could build your base structures and purchase units for a squad that followed you.
That reminds me, speaking of Arma 2, there's a mode in it called warfare that's almost exactly as I described and it's interesting, however with the way my computer is I can't really play more than an hour of it without it lagging because of how much stuff gets made. You can play it singleplayer with ai commanders and squads and stuff. There's also warfare be (benny edition) that I think has more stuff in it or something, idk. It seems to work better though.
btw I'm looking for games that can be played in singleplayer as well because that's my kinda thing.