A competitor in the 2018 Advanced Combat Skills Assessment uses a range finder during the mental and physical challenge, 19 June 2018, on Andersen Air Force Base, Guam. The ACSA tested security forces teams from throughout the Pacific Air Forces on core tasks of base defense, to include landnav, tactics, mental and physical challenges, and weapons firing. (U.S. Air Force photo/Senior Airman Zachary Bumpus)