Colonel (UNSC)

Colonel is a commissioned officer rank of the UNSC Marine Corps and UNSC Army, equal in rank to Captain in the UNSC Navy. Their rank insignia appears to be the same as their modern U.S. counterparts, one silver eagle.

Given that other ranks command the same unit groups as their modern day U.S. counterparts do, it is highly probably that a UNSC Colonel commands a regiment or a brigade. This has yet to be observed in the Halo universe though. A Colonel may also serve as a staff officer for higher unit groupings, such as divisions.