U.S. Air Force Staff Sgt. Chris Evans teaches Electronic Warfare Counter Measures (ECM) systems theory to former Communication Navigation (COMNAV) Airmen at Rosecrans Air National Guard Base, Mo., Sept. 10, 2014. The ECM and COMNAV career fields officially merged into one career field, Integrated Communication Counter Measures Navigation Systems, Aug. 1, 2014. (U.S. Air National Guard photo by Tech. Sgt. Theo Ramsey/Released)