SAN DIEGO (Dec. 7, 2020) Marines with Headquarters Battalion, 1st Marine Division participate in a Chemical, Biological, Radiological, and Nuclear Defense response during Steel Knight/Dawn Blitz (SK/DB) 21 on Marine Corps Air Station Miramar, Calif., Dec. 7, 2020. SK/DB 21 affords 1st Marine Division the opportunity to showcase its readiness within the education, planning, and execution continuum. (U.S. Marine Corps photo by Cpl. Alexa M. Hernandez)