As early as June 9, 1941, in a memo, a need of a 150 mm gun to be carried for infantry support was indicated.4
On October 20, 1942, Hitler saw Alkett's plans and wanted 40-60 to be built as soon as possible.4 On February 7, 1943, it was decided that the first 40 were to be completed by May 12, 1943, with another 20 to be finished after that. Prototypes first appeared in 1943.
The Sturmhaubitze 43 howitzer was a specially developed to go in a ball mount. The 150 mm gun could fire a 83.8 lb HE shell 4,675 yards at a muzzle velocity of 787'/sec.6
The commander sat towards the rear and used a roof mounted periscope to see. The driver sat on the left side and had a sliding shutter visor similar to the Tiger I's.4,8 Later models had a periscope for the driver.4,8
From April 1944 on it had a ball mounted machine gun in the left had corner of the superstructure and a cupola for the commander. Late models installed a ball mounted machine gun in the hull and Schürzen (side skirts).4,8
Due to the excess weight caused by the superstructure the front two wheels were replaced by steel rimmed wheels.4