http://www.smashingames.com/games/steamofwar.html Steam of War.
Great game, you need to think tactically to succeed. it's short but fun.
A couple of hints i found quite useful;
*keep a scout next to your artillery, artillery can't actually see what they're shooting but scouts can see far enough.
*put damaged vehicles at the back, a damaged tank moves as fast as a artillery so use them as a back guard to soak fire away from the expensive artillery.