U.S. Marines from 3rd Battalion, 8th Marines, utilize a makeshift terrain model prior to a ground assault, while participating in Integrated Training Exercise 3-15, at Marine Corps Air Ground Combat Center Twentynine Palms, Calif., May 17, 2015. MCAGCC conducts relevant live-fire combined arms training, urban operations, and joint/coalition level integration training that promotes operational forces readiness. (U.S. Air Force photo by Senior Airman Juan A. Duenas/Released)