Command Sergeant Major (CSM) is an E-9 rank of the UNSC Army and is a senior non-commissioned officer. It is equal in grade but not rank to Sergeant Major. It's the equivalent to the rank of Command Master Chief Petty Officer in the UNSC Navy, Sergeant Major in the UNSC Marine Corps, and Command Chief Master Sergeant in the UNSC Air Force.
A Command Sergeant Major serves as NCO of a battalion or larger unit. These positions are named with the name of the unit size followed by Sergeant Major, as in "Battalion Sergeant Major" or "Brigade Sergeant Major."
The CSM is responsible for all enlisted personnel within his/her unit, and represents them in the unit headquarters.