Sergeant Major of the Marine Corps

Sergeant Major of the Marine Corps was the highest rank that could be held by an enlistee within the Republic Marines. Selected from those holding the rank of sergeant major, the rank&mdash;and the resulting office&mdash;was only held by one being at a time. Promotion to this rank was at the appointment of the Commandant of the Marines, upon the retirement of the previous holder. Candidates were shortlisted based on a number of factors including combat history, service record, and citations or recommendations.

Those who served in this position worked as advocates for the enlisted personnel and non-commissioned officers within the Marine Corps, occasionally liaising with senior officers from the 's and  as well as their counterparts in those branches. More frequently, their duties involved advising the sitting Commandant in regards to officer-enlisted relations and the general mood of enlistees and non-commissioned officers.

Behind the scenes
The concept of this rank is based on its real-world counterparts in the, ,  and , all of which have their own "top enlisted rank."