U.S. Marines with 5th Marine Regiment, 1st Marine Division, I Marine Expeditionary Force (I MEF), set up camouflage netting while wearing mission-oriented protective posture suits and M50 joint service general purpose masks to protect from a simulated chemical attack during Exercise STEEL KNIGHT 14 aboard Marine Corps Air Ground Combat Center Twentynine Palms, Calif., December 14, 2013. STEEL KNIGHT enables participating I MEF units to hone their conventional warfighting capabilities by practicing the skills needed to deploy and fight as part of a Marine Air Ground Task Force. (U. S. Marine Corps photo by CWO3 Benn Barr, 1st Marine Division Combat Camera/Released)