Battlefield 3's Back to Karkand expansion pack launched yesterday, and EA is celebrating the launch with a new gameplay trailer. From EA: "This launch trailer features gameplay footage from the legendary Battlefield map Sharqi Peninsula, now reimagined and powered by the Frostbite 2 engine." If you've got the Limited Edition version of Battlefield 3, the Back to Karkand expansion is yours free. If not, you're out of luck. Or out $15. One or the other.