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 used a Panzer IV chassis with the upper hull and turret replaced by a new casemate-style armoured superstructure housing a new gun, the "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 ( for an HE shell and for a propellant cartridge) made the work of the loader arduous, especially if the gun was elevated to a high angle.