When I was in the National Guard, I was in a ROC unit. ROC means Rear Operations Center, and it was the rear command post for the XVIII Airborne Corps. What that means is that while the regular army guys ran the battle in the main command post, our job was to make sure that all of the supplies and replacements got up to the battle. Our secondary mission was to take over the battle if the main command post was taken out.
Every year we had to take part in a War Fighter exercise. War Fighters are exercises that help to train officers and senior sergeants how to run the headquarters. Most captains have to take a staff position to get their ticket punched and prove that they are worthy for promotion to major. Sergeants have to move to staff positions since most units don’t need a lot of master sergeants or sergeant majors.
The common thread here is that this is where they got trained for the staff jobs they had to do instead of leading soldiers in combat.