ARMA thrives in this area, and a recent expansion to ARMA 3: S.O.G. Prairie Fire is a great entry point for those who don’t play milsim games typically. There’s a beautifully crafted campaign that is designed as coop first, and was made with input from former US Special Forces MACV-SOG members.

Outside of this example, the community has scenarios like Antistasi, which is a dynamic gamemode that consists of two factions fighting to control a region, and your third insurgent force taking over. No scripted events, just AI making tactical decisions in response to your actions. The most predictable things are QRFs and increasing attacks on your positions as your war levels increase.

I have never had a session of Antistasi turn out similarly, other than people attaching to the roles they love (pilot,engineer,medic,etc.) Mods increase this to a next-level experience with TFAR for radio simulation, ACE for improved ballistics and medical systems, etc. There is a LOT to find, from WW2 to present day.

There are other more roleplay style servers, and I had a blast creating execution videos of in-game politicians and carbombing city squares on a roleplay server in 2014 or so as the Islamic State.

Great fun, great skills you can learn here (I learned a LOT about logistics and communications from ARMA, Foxhole, and Squad.) Game actually runs decently now too.

Check out “War of Rights”, it’s much like this.

Be warned that the community is incredibly toxic - but even so, it’s an interesting peek into the mindset of a typical soldier in that type of warfare. There is extremely little information available to you; you very rarely know if the round you just fired (that you spent thirty seconds loading) hit anything.