Senior Airman Paul Lopes, 51st Security Forces Squadron Combat Readiness Course instructor, returns simulated fire as he fends off 51st SFS defenders during a CRC, Dec. 19, 2019, at Osan Air Base, Republic of Korea. The course challenges Osan’s newest defenders on their readiness and skills to defend the base. (U.S. Air Force photo by Staff Sgt. Greg Nash)