U.S. Air Force Lt. Col. William Clayton, 20th Force Support Squadron commander, performs a pull-up during a 20th Security Forces Squadron Combat Challenge at Shaw Air Force Base, S.C., March 24, 2017. Airmen participated in teams through the challenge and were pushed physically and mentally through a series of obstacles, games and team workouts. (U.S. Air Force photo by Airman 1st Class Christopher Maldonado)