This is a story related achievementand cannot be missed.
SPOILER
Mission: Assault
Once you destroyed the AA guns you will get the quest to destroy a huge korean cruiser which can be found in the harbor. Once on it kill all the enemies on your way and go to the control room. Once finished with this step you will have to destroy it with an air strike. Go off and just to be sure like 50 to 100 meters away and then lock on with your binoculars.