Player Embed Code: Download Embed Share DOD News Update: SEAC Responsibility Shifts to Army Command Sgt. Maj. John W. Troxell Defense.gov Dec. 11, 2015 | 0:59 Army Command Sgt. Maj. John W. Troxell assumed responsibility as senior enlisted advisor to the chairman of the Joint Chiefs of Staff from Marine Corps Sgt. Maj. Bryan B. Battaglia. Troxell is the third person to serve in the position since its creation in 2005.