Staff Sgt. Michael Gwin, 28th Security Forces Squadron military working dog handler, his dog Rex, and Airman Keith Leflore, 28th SFS defender, stand ready at the gate at Ellsworth Air Force Base, S.D., April 25, 2013. Defenders guard the Liberty Gate 24 hours a day by defenders to keep the base secure. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)