U.S. Marine Corps Lance Cpl. Brandon J. Pena, top,

U.S. Marine Corps Lance Cpl. Brandon J. Pena, top, and Lance Cpl. William B. Salvate, bottom, both riflemen with Alpha Company, 1st Battalion, 6th Marine Regiment, 2nd Marine Division (MARDIV), provide security for the company as they execute a cliff assault, during basic mountain training at the Marine Corps Mountain Warfare Training Center in Bridgeport, Calif., Sept. 17, 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)