Army Staff Sgt. Mark Mercer, foreground, reassembles an M-16A2 rifle during the Army Training and Doctrine Command Drill Sergeant of the Year competition on Fort Jackson, S.C., Sept. 8, 2015. Mercer, a Reserve drill sergeant assigned to the 98th Training Division, is in a head-to-head competition with Army Staff Sgt. Russell Vidler. U.S. Army photo by Sgt. 1st Class Brian Hamilton