U.S. Army paratroopers, assigned to 4th Battalion, 319th Airborne Field Artillery Regiment, 173rd Airborne Brigade, check their protective masks before entering the gas chamber to conduct Chemical Biological Radiological Nuclear training at the 7th Army Joint Multinational Training Command's Grafenwoehr Training Area, Germany, March 31, 2015. The 173rd Airborne Brigade is the Army Contingency Response Force in Europe, capable of projecting ready forces anywhere in the U.S. European, Africa and Central commands areas of responsibility within 18 hours. (U.S. Army Photo by Visual Information Specialist Markus Rauchenberger/released)