A U.S. Marine with Headquarters Battalion, 1st Marine Division (1st MARDIV), writes in a log book while participating in a chemical biological radiological and nuclear drill during Exercise Steel Knight aboard Camp Pendleton, Calif., Dec 11, 2013. Steel Knight enables 1st MARDIV to test and refine its command and control capabilities by acting as the headquarters element for a forward-deployed Marine expeditionary force. (U.S. Marine Corps photo by Lance Cpl. Adrianna Stalker, 1st Marine Division Combat Camera/Released)