Chess but with Tanks

Indie developers Urban Squall came out with the first of the Battalion java games several years ago.  Since then, each new addition to this turn-based military strategy game has been an improvement over the last.  There's even the Battalion: Arena, where players can challenge the AI, one another, or conduct team battles on custom maps.  All of the Battalion chapters are hosted and available for free play at Kongregate.com. 

I'd recommend starting with Nemesis and working your way up.  But listen; don't start playing these damn games unless you have at least a week of obsessive gaming time to devote to them.  Because that's what'll happen.