Me, I like my video game wars unrealistic enough that I can cross an entire battlefield in five carefully-placed strafejumps but you, you may fancy them more simmy. If you like your shooty-shoots militaristic and damned demanding, yet you haven't hopped into the Arma 3 [official site] APC yet, hey: give it a go, as the whole game's free to try in a free trial weekend on Steam.
The free weekend version includes most of Arma 3, except its paid DLC and the second and third chapters of its singleplayer campaign. Beyond that, sure, go wild, run around in the hills with your pals, carefully follow the virtual reality training, check out its multiplayer modes, go play weird player-made scenarios, go play serious player-made scenarios, fiddle with the scenario editor to make your own, or try to join a virtual battalion and be screamed at by a virtual drill sergeant with a crackly microphone. You can play most of Arma 3, I'm trying to say.
You should find Arma 3 in your Steam Library now if you want to install it. The trial will end at 10pm on Sunday, while the big Bohemia sale will end on Monday.