U.S. Marine Corps Staff Sgt. Jeremy H. Miller, left,

U.S. Marine Corps Staff Sgt. Jeremy H. Miller, left, instructor team leader, Marine Corps Mountain Warfare Training Center (MCMWTC), teaches Marines with Alpha Company, 1st Battalion, 6th Marine Regiment, 2nd Marine Division (MARDIV), about mountain weather conditions, during a pre-environmental training class prior to the start of Mountain Exercise 5-15 at MCMWTC, Bridgeport, Calif., Sept. 6, 2015. Marines participate in a month-long field exercise focusing on core mission essential tasks such as assault climbing, animal packing and small unit movements, to strengthen expeditionary high altitude warfare tactics in a mountainous environment against a hybrid threat, as they prepare for world-wide deployment. (U.S. Marine Corps photo by Cpl. Kelly L. Street, 2D MARDIV COMCAM/Released)