The Sturmpanzer was a development of the Panzer IV tank designed to provide a vehicle offering direct infantry fire support, especially in urban areas. It was known by the nickname Brummbär (German: "Grouch") by Allied intelligence, a name which was not used by the Germans. German soldiers nicknamed it the "Stupa", a contraction of the term Sturmpanzer. Just over 300 vehicles were built and they were assigned to four independent battalions.
It used a Panzer IV chassis with the upper hull and turret replaced by a new casemate-style armored superstructure housing a new gun, the 15-centimetre (5.9 in) Sturmhaubitze (StuH) 43 L/12 developed by Skoda. It fired the same shells as the 15 cm sIG 33 heavy infantry gun. Thirty-eight rounds, with separate propellant cartridges, could be carried. It used the Sfl.Zf. 1a sight. The combined weight of the shell and cartridge (38 kilograms for an HE shell and 8 kilograms for a propellant cartridge) made the work of the loader arduous, especially if the gun was elevated to a high angle.
