The devil's Brigade has been created at first in the WWII as a join force of the US-Canada unit who fough behind 1942-1944 in artic condition and mountain climbing This unit was the most decorated force of the allied armies. It became a legend and was a precursor in the special force.
The UNSC finally reactivated this unit in early October 2594 for special operation. It has the exactly same number of soldier. The unit fough during the whole war and wasn't desactivated. This unit was under the command of Colonel Genevieve Tanner and was an ODST force extremly effective. Some of the other Marines and odst force said about it that they were hungry for blood and fought with unparalleled verocity.