Marines with 1st Marine Division take part in a Combined Armed Staff Trainer exercise aboard Marine Corps Base Camp Pendleton, Calif., Nov. 17, 2015, in preparation for Exercise Steel Knight 2016. The CAST exercise was a division-level evolution, which allowed Marines to maintain designated skillsets in support of a simulated, large-scale operation.(U.S. Marine Corps photo by Cpl. Demetrius Morgan/RELEASED) - Marines with 1st Marine Division take part in a Combined Armed Staff Trainer exercise aboard Marine Corps Base Camp Pendleton, Calif., Nov. 17, 2015, in preparation for Exercise Steel Knight 2016. The CAST exercise was a division-level evolution, which allowed Marines to maintain designated skillsets in support of a simulated, large-scale operation.(U.S. Marine Corps photo by Cpl. Demetrius Morgan/RELEASED)