I'm playing World Of Tanks beta right now. The MMO is designed around WWII tank battles where you start out with a small insignificant tank and work towards higher tier tanks, tank Destroyers, and Self propelled Artillery guns, and advancing your tanks crews.
There is going to be clan based functions where you battle for and defend terratories on a European battle map.
Currently there is the German and Russian lines with the US line being patched in within the next week or 2.
http://game.worldoftanks.com/about