There is a free First / Third person MMORP Game called world of tanks. It take pre WWII tank to end of WWII tanks from German, USA, USSR. You advance down the tech tree of each country researching new tanks, artillery, and Anti-Tanks Tanks. Each one you research new tracks, guns, radios, engines and turrents. All of it based off the real tanks of that era and what mods they actually had. The battles are usually 15vs15 with some matches being 4v4 also you can platoon up if you buy a premium account. New patch that coming out allows free 2 person platoons. Has built in voice chat, the graphics are great, controls are simple and easy to get use too.
If your playing it add me to your friends list also we can create a tank company.