Squad is a good army simulation game i recommend finding a good rp server where people actually take everything serious you enjoy yourself more when you got like a whole squad who actually listen and not just do what ever they want which you normally get on most servers. well speaking from my experience
There is something similar but World War 2/1 Related one wich i like better in my opinion Call of arms might be complicated and weird to understand at the beginning.
Rainbow Six: Vegas 2. That is if you can deal with the 65 FOV as I can only play it for 15 minutes at a time without being sick but, it is an awesome game.
Escape from Tarkov is pretty tactical if that is what you are looking for.