Stormtroopers, a term used to apply to specialized units during the Great War who had mastered the art of trench raiding. So effectively, that they were generally able to traverse the distance between the two trench lines with little to no exposure in no-man's-land.
It was an entirely alien concept that made use of small, specialized teams, which were highly mobile, and equipped with the most modern of weapons. Realistically, the submachine guns, semi-automatic rifles, and general-purpose machine guns that were currently being produced to replace the older weapon platforms would be ideal for this conflict.
But these weapons were state secrets of the German Reich. And because of this, Bruno chose to make use of older equipment that he had already displayed in the Russian Civil War. Such as the Mauser C96 "Trench Carbine" which was based upon the 1917 prototype that was beaten by the MP 18 during military trials. Albeit with an added select fire capability.