Marines with 1st Combat Engineer Battalion, 1st Marine Division, I Marine Expeditionary Force, fire antipersonnel obstacle breaching systems during Exercise Pioneer Express at Camp Roberts, Calif., Sept. 8, 2015. The exercise prepares Marines to successfully execute expeditionary operations by refining command and control methods, reconnaissance, mobility, counter-mobility and survivability operations. (U.S. Marine Corps photo by Lance Cpl. Caitlin Bevel) - Marines with 1st Combat Engineer Battalion, 1st Marine Division, I Marine Expeditionary Force, fire antipersonnel obstacle breaching systems during Exercise Pioneer Express at Camp Roberts, Calif., Sept. 8, 2015. The exercise prepares Marines to successfully execute expeditionary operations by refining command and control methods, reconnaissance, mobility, counter-mobility and survivability operations. (U.S. Marine Corps photo by Lance Cpl. Caitlin Bevel)