5th Infantry Regiment
This Regiment was only ever raised as two battalions - The first was well equipped to TL–15 standards and undertook the Duke's enforcement actions while the second was equipped to just TL–13 and undertook security duties. Both were notionally elite units, but were in fact pampered and polished for ceremonial to the point where they spent little time in the field.
The Regiment was formally an auxiliary of the Imperial Marines but was never considered to be equipped or trained to current standards. The Imperial Marines tended to deride its members as "Toy Soldiers" because of their emphasis on appearance and political deployments.
The 5th "Duchy of Khouth" Infantry Regiment was formed when Khouth joined the Imperium. The Regiment's number came from the lowest number in service to the planet at the time the Imperial Army absorbed the planet's colonial forces. (Regiments 1-4 had all been destroyed fighting the Vargr in the previous decade).