Airman 1st Class John Stumpf, 28th Security Forces Squadron response force member, inspects a commercial truck prior to authorizing entrance to Ellsworth Air Force Base, S.D., Feb. 10, 2016. Security forces personnel are the Air Force's first line of defense and it is their job to uphold the law on all Air Force installations. (U.S. Air Force photo by Airman 1st Class Denise M. Nevins/Released)