Airmen assigned to the 28th Aircraft Maintenance Squadron duck and cover after a simulated attack during the Phase II portion of an operational readiness exercise at Ellsworth Air Force Base, S.D., July 11, 2013. This Phase II exercise demonstrated Airmen’s ability to respond to simulated threats and attacks as well as treatment to injured and contaminated victims that might become necessary in the event of a real-world emergency. (U.S. Air Force photo by Staff Sgt. Mark Leahy/Released)