Within the Imperial Army, the title High Colonel is bestowed upon the officer who commands a battlegroup. Likewise, in the Stormtrooper Corps, it designates the officer in charge of a legion. Notably, for the Stormtrooper Corps, "High Colonel" represents the uppermost echelon in their entire ranking system.
Typically, a High Colonel would oversee four regiments, which translates to a little over 10,000 combat-ready soldiers. The immediately superior rank to High Colonel is that of Major General. This command structure represented a substantial military asset, generally deployed for prolonged operations against well-organized adversaries, although Imperial Army strategists deemed it insufficient for conquering or pacifying an entire planet.
An example of such an operation occurred on Picutorion, where High Colonel Theol Drost collaborated with Commodore Bevven from the Imperial Navy.
The Imperial Sourcebook is the origin of the High Colonel rank. These officers outrank the Lieutenant Colonels who command regiments, but are subordinate to the Major Generals in command of corps. It is suggested that the battlegroups commanded by High Colonels are new formations, similar to the old divisions.
Beyond this initial mention, established canon lacks explicit details regarding the High Colonel's precise position in the Imperial Army's hierarchy, leaving several possibilities open:
- A rank analogous to a Brigadier General in the real world (NATO code OF-6), but classified as a field officer instead of a general officer. Real-world examples include the British Army's brigadier rank and its predecessor "Colonel-Commandant" (1922-1928), as well as the former Swedish Army rank of Överste av första graden (senior colonel).
- Simply a full colonel, in contrast to a Lieutenant Colonel.
- An inserted rank between colonel and brigadier.
- A designation, rather than a formal rank, indicating an officer in command of a battlegroup. Supporting this idea, in the Lords of the Expanse RPG scenario, Tessala Corvae, an Imperial officer, leads the 1st Tapani Assault Battlegroup – a command level where we would expect to find a High Colonel. Although she is repeatedly referred to as a Major General, her RPG statistics list her as wearing a "Colonel's uniform".
- A title to differentiate an officer in command of a division without giving them flag rank. In the Stormtrooper Corps, this would prevent a Legion commander on an Imperial Star Destroyer from outranking the ship's captain.
Given that the source material describes the battlegroup as a newly-established command level replacing the division, it is plausible that the rank of High Colonel was created concurrently. Furthermore, the lifespan of "High Colonel" may have been as brief as the British Army's "Colonel-Commandant" rank.
The rank insignia for High Colonel is often described as consisting of six yellow squares, accompanied by a code cylinder on each side of the badge. However, this is merely speculative fanon, apparently originating from the Imperial Insignia page on the Star Wars Technical Commentaries website.