Fay, 375th SFS military working dog, performs an escort during muzzle aggression training March 20, 2015, at the 375th SFS Military Working Dog Kennels at Scott Air Force Base, Ill. K-9s can work with the military, depending on their health, they can be retired due to medical conditions or until they are eight, which is when most kennels try to retire their dogs. (U.S. Air Force photo/ Senior Airman Tristin English)