Sgt. Eric Masters, mountain leader instructor, Marine Corps Mountain Warfare Training Center, conducts a weapons check before going to the night vision live-fire range aboard the training center, Feb. 20, 2014. During the day the Marines traveled long distances, and at night coordinated battle skills while on the same challenging terrain. - Sgt. Eric Masters, mountain leader instructor, Marine Corps Mountain Warfare Training Center, conducts a weapons check before going to the night vision live-fire range aboard the training center, Feb. 20, 2014. During the day the Marines traveled long distances, and at night coordinated battle skills while on the same challenging terrain.