U.S. Marines with 1st Battalion, 6th Marine Regiment,

U.S. Marines with 1st Battalion, 6th Marine Regiment, 2nd Marine Division (MARDIV), lead their pack mules back to lower base camp after transporting crew served weapons to the Forward, where the battalion has their front line defense, during Mountain Exercise 5-15 at the Marine Corps Mountain Warfare Training Center, Bridgeport, Calif., Sept. 22, 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)