Historical information:

The Sturm-Infanteriegeschütz 33B was a German self-propelled heavy infantry gun used during World War II. A new, fully enclosed, and heavily armored superstructure was built on the chassis of the Sturmgeschütz III. It mounted the improved sIG 33/1 infantry gun, offset to the right side, for which 30 rounds were carried. It could only traverse 3° left and right, elevate 25°, and depress 6°. A Maschinengewehr 34 machine-gun was fitted in a ball mount on the left side of the superstructure with 600 rounds. Its traverse limits were 15° left and 20° right, and it could elevate 20° and depress 10°.

Sources differ as to the development history. Chamberlain and Doyle say that Alkett was ordered in July 1941 to convert a dozen Sturmgeschütz III Ausf. E chassis and that these were finished in December 1941 and January 1942 - but not issued. On 20 September 1942, another dozen Sturmgeschutz IIIs were ordered to be converted, and the existing vehicles were rebuilt. Trojca and Jaugitz contend that all twenty-four were built by Alkett starting in September 1942 from repaired Sturmgeschütz III Ausf. B, C, D and E chassis.

The first dozen were delivered by the end of October 1942 and assigned to Sturmgeschütz-Abteilungen (Assault Gun Battalions) 177 and 244, then fighting in Stalingrad. The remaining dozen vehicles could not be delivered to Sturmgeschütz-Abteilungen 243 and 245, also fighting in Stalingrad, after the Soviets surrounded the German 6th Army on 21 November. Instead, the vehicles were formed into Sturm-Infanterie-Geschütz-Batterie/Lehr-Bataillon (Assault Infantry Gun Batterie/Demonstration Battalion) XVII. The battalion was assigned to the 22nd Panzer Division as the Germans attempted to relieve the trapped 6th Army. The Division was virtually wiped out in the fighting and the battery was assigned to the 23rd Panzer Division where it became the Sturm-Infanterie-Geschütz-Batterie/Panzer-Regiment 201 (also known as 9. Kompanie/Panzer-Regiment 201) for the rest of the war. The last strength report to mention them lists five remaining in September 1944.