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How to Obtain: Complete a Special Ops Mission Mode game on Hardened or Veteran with no player getting downed.
The best and easiest map to do this is on is "Milehigh Jack". As its quite short and not much room for the enemy AI to maneuver, it's the perfect place. I'd start out on a lower difficulty to get where people spawn, and what's best when.
Just be on your toes, and using your flashbangs is a must. The only hiccup in this level is the timer, but once you know what you're doing, it's a breeze. For more helpful info on some Veteran tactics please see the "The Best of the Best" achievement up top.
Antother great map is resistance movement. Once again, use the easier difficulties to get a feel for the level, then do one of the harder difficulties to learn the specifics of those difficulties. Practice, don't worry about civilians, and just try as hard as you can.