Republic of Korea Marines quickly put on gas masks June 3 at Doksukri Training Area, Republic of Korea, during Korean Military Exchange Program 15-9. U.S. and ROK Marines took nuclear, biological and chemical individual safety measures while practicing water purification procedures in midst of a simulated attack. The ROK Marines are with Engineer Battalion, 1st ROK Marine Division. The U.S. Marines are with 9th Engineer Battalion, 3rd Marine Logistics Group, III Marine Expeditionary Force. (U.S. Marine Corps photo by Cpl. Joey S. Holeman, Jr./ Released)