Staff Sgt. Juan Fisher, 11th Marine Expeditionary Unit embarkation chief, re-enlists during a hike on Oct. 25, 2013. For most of the hike, the Marines wore Mission Oriented Protection Posture, or MOPP gear. The Marines wore the gear because during the hike, they were exposed to CS gas as part of their annual Chemical, Biological, Radiological and Nuclear training. U.S. Marine Corps photo by Gunnery Sgt. Rome Lazarus/Released.