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Description
Overview:*
In October of 1942, Alkett presented a design that mated a Skoda-built ball-mounted 15cm sIG Infantry Gun to a heavily armored Pzkpfw-IV chassis. The company provided a wooden mockup in spring 1943. The company presented it to Hitler who approved of the proposal ordering the manufacture of 40 to 60 before the summer (Kursk) Offensive. Production quickly commenced in April of 1943 using a combination of new and rebuilt Pzkpfw-IV hulls. Problems in manufacture caused fabrication of the StuPz-IV to stall until December of 1943. However, by January 1944 production commenced on schedule and continued until the end of the war. The army placed StuPz-IVs in specialized StuPz Battalions that acted independently from other units. These units saw action on East, West, and Italian Fronts. Early and mid-production vehicles had problems with suspension and drive train due to an over stressed chassis. However, late series had remedied these problems with weight reduction of the main armament and the replacement of rubber-tired road-wheels with steel road-wheels. Overall, the StuPz-IV proved to be an effective weapon in its role.

Production:
Alkett manufactured 46 StuPz-IVs in April and an additional 14 in May. All of these vehicles were early-series with about 15% fabricated on old Auf-E & Auf-F chassis. As mentioned before, a delay in production prevented the mid-series StuPz-IV from starting until December of 1943. Alkett produced 80 mid-series until switching to the late-series in May of 1944. By the war's end, Alkett had manufactured 166 late-series StuPz-IVs.

Design:
StuPz-IV had a large boxlike superstructure mounted on a Pzkpfw-IV Chassis. The front of the superstructure was made-up of a 100mm thick, well-sloped glacis plate. Designers fixed the main armament in a specialized ball mount for the 15cm StuH43. This arrangement allowed a wide range of traverse for the main armament of a non-turreted AFV. The StuPz-IV had a number of noticeable changes made during its manufacture, these features fall into three basic categories Early, Mid and Late.

Series Modifications:
The SturmPanzer-IV production can be divided into three stages - early, mid and late.
Early: (Displayed the following prominent features)
- A Pzkpfw-IV Auf-E, F or G chassis.
- 50mm thick applique armor bolted to the front hull.
- A Fahrersklappe-80 driver's visor.
- Three split hatches in the superstructure roof for crew entrance/exit.
- Two antennas mounted on the superstructure rear.
- Two fume extractors mounted under armored covers on superstructure rear below each antenna.
- 20mm thick applique armor bolted to the lower sides of the hull.
Mid:(Had the following features or changes made to its superstructure)
- A Pzkpfw-IV Auf-H chassis.
- Elimination of 50mm thick applique armor bolted to the front hull.
- Elimination of Fahrersklappe-80 driver's visor.
- Addition of a rotating periscope for driver.
- Split hatches reduced from three to two.
- Addition of sliding periscope mount to the superstructure roof.
- Addition of a splash guard in front of the commander's entrance hatch.
- Elimination of the antenna on the left rear superstructure.
- Elimination of one fume extractor fan.
- Moving the remaining fume extractor fan to the front superstructure top.
- Addition of a pistol port to the rear of both superstructure sides.
- Elimination of the Bosch headlight on the right front mud guard.
- Replacement of the original 15cm StuH 43 with a new light-weight StuH 43/1.
Late:(Had the following features or changes made to its superstructure & suspension)
- A Pzkpfw-IV Auf H or J chassis.
- Simplified casemate composed of five plates instead of seven (ie. front, sides, rear and roof).
- Addition of a Kugelblende-80 ball mounted machine gun to the front-left superstructure.
- Addition of a second fume extractor fan above machine-gun position.
- Elimination of the crew's large split-hatch on the right side of the superstructure top.
- Addition of two small hatches in place of the previously mentioned hatch.
- Replacement of the commander's split-hatch with a Sturmgeschütz-III G commander's hatch.
- Addition of a boxlike structure with a split entrance hatch to the rear superstructure.
- Addition of an anti-aircraft machine gun mount next to the commanders cupola (not all).
- Replacement of the rubber rimmed road-wheels with steel-rimmed road-wheels.

Combat:
Officials issued all vehicles to four independent Sturm panzer Abteilungs (Battalions). Each Abteilung was composed of about 45 StuPz-IVs. Each Abteilung consisted of three companies each comprised of 14 StuPz-IVs. Every company had one HQ section, with two command StuPz-IVs, and three platoons each composed of four StuPz-IVs.
--StuPz Abt.216: formed in April 1943, it participated in the Battle of Kursk, Group Center - July 1943. By February of 1944 the battalion was shipped to Italy where it participated in the Battle of Anzio, remnants remained in Italy until the end of the war.
--StuPz Abt.217: formed in April 1944, it entered combat at Normandy in the summer of 1944 during the D-day Invasion. It continued to fight on the West-Front until its eventual surrender in Germany at the end of the War.
--StuPz Abt.218: formed in January 1945, and entered combat on the East-Front against the Warsaw Uprising. It remained on the East-Front combating the Soviet Forces. Eventually the battalion was dissolved and remnant vehicles absorbed into PG Division 'Grossdeutchland'.
--StuPz Abt.219: formed in September 1944 in Germany. In December of the same year, the army moved it to Hungary where it participated against Soviet Forces in the Battle for Budapest; remnants relocated to Czechoslovakia where all vehicles were eventually lost.

Drawing:
This drawing depicts a mid production Sturmpanzer-IV with external equipment and schurzen.

*Note: The Sturmpanzer-IV was never known as the "Brummbär" by the Germans during the war; this was a term given by Allied sources. It was actually known as "Stupa" by German troops.

Description
Overview:*
In October of 1942, Alkett presented a design that mated a Skoda-built ball-mounted 15cm sIG Infantry Gun to a heavily armored Pzkpfw-IV chassis. The company provided a wooden mockup in spring 1943. The company presented it to Hitler who approved of the proposal ordering the manufacture of 40 to 60 before the summer (Kursk) Offensive. Production quickly commenced in April of 1943 using a combination of new and rebuilt Pzkpfw-IV hulls. Problems in manufacture caused fabrication of the StuPz-IV to stall until December of 1943. However, by January 1944 production commenced on schedule and continued until the end of the war. The army placed StuPz-IVs in specialized StuPz Battalions that acted independently from other units. These units saw action on East, West, and Italian Fronts. Early and mid-production vehicles had problems with suspension and drive train due to an over stressed chassis. However, late series had remedied these problems with weight reduction of the main armament and the replacement of rubber-tired road-wheels with steel road-wheels. Overall, the StuPz-IV proved to be an effective weapon in its role.

Production:
Alkett manufactured 46 StuPz-IVs in April and an additional 14 in May. All of these vehicles were early-series with about 15% fabricated on old Auf-E & Auf-F chassis. As mentioned before, a delay in production prevented the mid-series StuPz-IV from starting until December of 1943. Alkett produced 80 mid-series until switching to the late-series in May of 1944. By the war's end, Alkett had manufactured 166 late-series StuPz-IVs.

Design:
StuPz-IV had a large boxlike superstructure mounted on a Pzkpfw-IV Chassis. The front of the superstructure was made-up of a 100mm thick, well-sloped glacis plate. Designers fixed the main armament in a specialized ball mount for the 15cm StuH43. This arrangement allowed a wide range of traverse for the main armament of a non-turreted AFV. The StuPz-IV had a number of noticeable changes made during its manufacture, these features fall into three basic categories Early, Mid and Late.

Series Modifications:
The SturmPanzer-IV production can be divided into three stages - early, mid and late.
Early: (Displayed the following prominent features)
- A Pzkpfw-IV Auf-E, F or G chassis.
- 50mm thick applique armor bolted to the front hull.
- A Fahrersklappe-80 driver's visor.
- Three split hatches in the superstructure roof for crew entrance/exit.
- Two antennas mounted on the superstructure rear.
- Two fume extractors mounted under armored covers on superstructure rear below each antenna.
- 20mm thick applique armor bolted to the lower sides of the hull.
Mid:(Had the following features or changes made to its superstructure)
- A Pzkpfw-IV Auf-H chassis.
- Elimination of 50mm thick applique armor bolted to the front hull.
- Elimination of Fahrersklappe-80 driver's visor.
- Addition of a rotating periscope for driver.
- Split hatches reduced from three to two.
- Addition of sliding periscope mount to the superstructure roof.
- Addition of a splash guard in front of the commander's entrance hatch.
- Elimination of the antenna on the left rear superstructure.
- Elimination of one fume extractor fan.
- Moving the remaining fume extractor fan to the front superstructure top.
- Addition of a pistol port to the rear of both superstructure sides.
- Elimination of the Bosch headlight on the right front mud guard.
- Replacement of the original 15cm StuH 43 with a new light-weight StuH 43/1.
Late:(Had the following features or changes made to its superstructure & suspension)
- A Pzkpfw-IV Auf H or J chassis.
- Simplified casemate composed of five plates instead of seven (ie. front, sides, rear and roof).
- Addition of a Kugelblende-80 ball mounted machine gun to the front-left superstructure.
- Addition of a second fume extractor fan above machine-gun position.
- Elimination of the crew's large split-hatch on the right side of the superstructure top.
- Addition of two small hatches in place of the previously mentioned hatch.
- Replacement of the commander's split-hatch with a Sturmgeschütz-III G commander's hatch.
- Addition of a boxlike structure with a split entrance hatch to the rear superstructure.
- Addition of an anti-aircraft machine gun mount next to the commanders cupola (not all).
- Replacement of the rubber rimmed road-wheels with steel-rimmed road-wheels.

Combat:
Officials issued all vehicles to four independent Sturm panzer Abteilungs (Battalions). Each Abteilung was composed of about 45 StuPz-IVs. Each Abteilung consisted of three companies each comprised of 14 StuPz-IVs. Every company had one HQ section, with two command StuPz-IVs, and three platoons each composed of four StuPz-IVs.
--StuPz Abt.216: formed in April 1943, it participated in the Battle of Kursk, Group Center - July 1943. By February of 1944 the battalion was shipped to Italy where it participated in the Battle of Anzio, remnants remained in Italy until the end of the war.
--StuPz Abt.217: formed in April 1944, it entered combat at Normandy in the summer of 1944 during the D-day Invasion. It continued to fight on the West-Front until its eventual surrender in Germany at the end of the War.
--StuPz Abt.218: formed in January 1945, and entered combat on the East-Front against the Warsaw Uprising. It remained on the East-Front combating the Soviet Forces. Eventually the battalion was dissolved and remnant vehicles absorbed into PG Division 'Grossdeutchland'.
--StuPz Abt.219: formed in September 1944 in Germany. In December of the same year, the army moved it to Hungary where it participated against Soviet Forces in the Battle for Budapest; remnants relocated to Czechoslovakia where all vehicles were eventually lost.

Drawing:
This drawing depicts a mid production Sturmpanzer-IV with external equipment and schurzen.

*Note: The Sturmpanzer-IV was never known as the "Brummbär" by the Germans during the war; this was a term given by Allied sources. It was actually known as "Stupa" by German troops.