Want 15 easy Achievement points? Here's a quick guide to getting "Assault Trooper". Load up Call of Duty 3 and play The Island (mission 2) on Easy. Use only the BAR sparingly in 1 and 2 shot bursts, and melee and use grenades as often as possible. Let your squadmates deal with the spray-and-pray. If you only use the BAR, and finish the mission, you'll get it. Enjoy your Achievement!