Colonel

ColonelHalo: Ghosts of Onyx, page 58, "... pinned with the eagle insignia of a colonel." is the highest field grade commissioned officer rank of the UNSC Marine Corps, UNSC Army, and UNSC Air Force, equal in rank to a Captain in the UNSC Navy. The rank insignia appears to be the same as the modern U.S. counterpart, one silver eagle.
Given that other ranks command the same unit groups as their modern day U.S. counterparts do, it is highly probable that a UNSC Colonel commands an Air Force wing, Marine regiment or an Army brigade; this, however, has yet to be observed in the Halo universe. A Colonel may also serve as a staff officer for higher unit groupings, such as divisions.
==Sources==
Category:UNSC Air Force Ranks
Category:UNSC Army Ranks
Category:UNSC Officer Ranks
Category:UNSC Marine Ranks