This is a story related achievement and cannot be missed.
In the mission "Recovery" in the second half after rescuing the hostage there will be some tanks outside the building. Go to the armory stock up on ammo and fight your way out of the city. You will afterwards face a lot of korean troups i the woods and i recommend you just run on highspeed trough their lines to complete the level quickly as they can get quite annoying. At the end of the mission you will find Prophet and the achievement should pop immediately.