Sturmpanzer IV Brummbar
Sturmpanzer IV Brummbar

Sturmpanzer IV Brummbär: Meet the Sd.Kfz. 166 Assault Gun!

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The “Brummbar,” officially designated as the SdKfz 166, was a formidable armored combat vehicle from late World War II (1939-1945), based on the Panzer IV (Panzerkampfwagen IV) Medium Tank. It is best known by its nickname, the “Brummbar,” and featured robust armor and weaponry.

Its primary armament consisted of a potent 150 mm field howitzer, and its primary role revolved around providing crucial support to ground forces, particularly in urban environments where its firepower could wreak havoc on structures.

The Sturmpanzer IV did not conform to the conventional tank design, as it did not feature a rotating turret. Instead, it housed its formidable howitzer armament within a fixed superstructure, earning it the classification of an “assault gun” rather than a traditional tank.

Naming Process of the Sturmpanzer IV Brummbär

The Sturmpanzer, alternatively referred to as Sturmpanzer 43 or Sd.Kfz. 166, was a German armored infantry support gun derived from the Panzer IV chassis and used on all fronts during World War II.

This vehicle saw action in pivotal battles such as Kursk, Anzio, and Normandy, and it played a role in the Warsaw Uprising.

Interestingly, Allied intelligence referred to it with the nickname “Brummbär” (German for “Grouch”), although this moniker was not actually used by the Germans themselves.

The German soldiers affectionately called it the “Stupa,” a shortened version of the term “Sturmpanzer.” Translated from German to English, “Sturmpanzer” means “Storm Tank,” while “Brummbär” translates to “Grizzly Bear.”

All views drawing of the Sturmpanzer IV <a href="" rel="nofollow"> Source</a>
All views drawing of the Sturmpanzer IV Source

Development on the Panzer IV Medium Tank Chassis

The Battle of Stalingrad highlighted a significant gap in the German army’s arsenal – a pressing need for an infantry support vehicle capable of delivering substantial fire support and destructive capability. This requirement was especially evident for a weapon that could efficiently reduce an average city house to rubble in just two or three shots, like the Sig 33 heavy infantry gun.

The existing vehicles were obsolete, with no viable stop-gap solutions in place, such as the sIG 33 B mounted on a Panzer III, or they were merely outdated, as seen in the case of the sIG models on Panzer I and II vehicles.

The self-propelled assault guns currently in service were fulfilling their roles as mobile artillery but faced a deficiency in armor protection for both the crew and vital components.

Originally designed for a specific purpose, the StuG III also faced a shortage of large-caliber guns suited for its intended role. So it increasingly found itself pressed into service as an improvised anti-tank solution.

As early as 1941, there was a recognition of the necessity for a vehicle of this kind. On June 9th of that year, a request was made to mount a 15 cm sIG on a heavily armored frame.

The demand for a novel self-propelled gun, partly influenced by Adolf Hitler himself, was firmly established in early 1942, as Germany found itself fully engaged in warfare on multiple significant fronts.

As the new “Panther” Medium and “Tiger I” heavy tanks started to proliferate, an opportunity arose that led to the relegation of the outdated Panzer III and Panzer IV series medium tanks to secondary roles or adaptations for other essential functions.

During the course of the war, the German Army frequently adopted alterations to existing tank models, including the Panzer 4 series. These modifications became a prevalent practice, especially towards the war’s conclusion, and served as cost-effective measures to meet battlefield requirements and attempt to alter the course of engagements

On the 14th of October 1942, Alkett, the German manufacturer, showcased their design blueprints to Hitler. Their concept featured a modified sIG (15 cm sIG 33) mounted on a Panzer IV, resembling the design of a Sturmgeschütz (StuG). Hitler gave his approval for the design and requested that the new sIG should fire thinly encased shells to enhance their high-explosive effectiveness.

Sturmpanzer IV Brummbar Prototype in 1943 <a href="<a href="" rel="nofollow"> Source</a>
Sturmpanzer IV Brummbar Prototype in 1943 Source

On February 7, 1943, the initial model photographs were presented to Hitler, and he stipulated a requirement for an initial production series of 40 vehicles. In an order issued on the same date, February 7, 1943, it was explicitly requested that these vehicles be finished by May 12, 1943.

Initially designated as “Gerät 581 – Sturmpanzerwagen 604/16 (ALKETT) sIG auf PIV mit kardanischem Fahrwerk” unofficially, this nomenclature was altered to Sd.Kfz 166 in April 1943.

Nonetheless, due to wartime shortages and resource allocations in other areas, there was a delay in the quantitative production for several months. It wasn’t until November of that year that production began to accelerate. Initially, the Sturmpanzer IV was designed to utilize rebuilt ex-Panzer IV tanks, but eventually, even new chassis were reconfigured to meet the increasing demand.

Following initial trials, it was determined that the new assault tank, equipped with a five-person crew, 38 rounds of ammunition, and a spacious fighting compartment, would have an estimated weight of 28.2 tons.

In contrast to the typical German wartime production approach for modified vehicles, Sturmpanzer IVs were actually manufactured within German Army facilities. Initially, production took place in Vienna, and later, starting from June 1944, it shifted to Duisberg, instead of relying on specialized company factories.

The StuH 43 L/12 – Gun of  the Self-Propelled Armored Vehicle

Skoda undertook the development of a new gun, resulting in the production of 6 units in March, 40 in April, and 14 in May. During the same month the gun received its official designation as the “15 cm Sturmhaubitze 43/1 (L/12)” or assault howitzer.

However, the short-barreled 15 cm (150 mm) StuH 43 L/12 series guns posed challenges. It was heavy for a tank chassis, and substantial recoil exceeded the design parameters of the superstructure, and the system’s sheer weight placed significant strain on the chosen engine installation, impacting both reliability and operational ranges.

The heavy infantry gun was mounted within a ball-type socket and had a relatively short length of only 12 calibers.

Machine guns served as a versatile defense against both infantry and low-flying aircraft. However, the crew of the Sturmpanzer IV typically depended on accompanying infantry units to fend off enemy anti-tank threats, as Stupa operations were characterized by deliberate, methodical street-by-street maneuvers, often at a slow and cautious pace.

Ammunition for the StuH 43

The “Brummbär” possessed the capability to utilize two distinct types of ammunition. It could fire the 15 cm lgr 38 FES, a high-explosive round weighing 38 kg, with a length of 660 mm, and a velocity of 240 m/second. Alternatively, it could deploy the 15 cm lgr 39 Hl/A, an anti-tank hollow charge round weighing 25 kg, measuring 572 mm in length, and traveling at a speed of 275 m/second.

Additionally, efforts were underway to develop a “mine grenade” although this project remained unfinished.

The crew compartment held a stockpile of 38 high-explosive (HE) projectiles, alongside 600 rounds of 7.92 mm ammunition for self-defense MG 34 gun(s) in case they were installed.

Crew members of Stupa <a href="<a href="" rel="nofollow"> Source</a>
Crew members of Stupa Source

Crew of the Stupa

The crew of the Sturmpanzer IV benefited from the protective design of the superstructure. Although the fighting compartment offered ample space for the necessary crew of four (later increased to five), the commander occupied the rear portion of the superstructure, directly behind the gun mount.

The commander utilized a rooftop periscope to designate targets for the gunner and provide guidance for field fire when necessary.

Among the crew, one or two members were responsible for managing ammunition, while a fourth crewmate operated the main gun. The fifth crew member assumed the role of the driver, positioned at the vehicle’s left front.

Sturmpanzer IV with extra side skirt armour in Italy, March 1944 Source
Sturmpanzer IV with extra side skirt armour in Italy, March 1944 Source

Armour of Sturmpanzers

The superstructure’s armor boasted sloped surfaces on all sides, including the roof. The frontal plate, in particular, featured a formidable thickness of 100mm (2.54 inches). However, the earlier models suffered from a vulnerability in their side armor, which was limited to a mere 30mm (1.18 inches). This made them susceptible to enemy anti-tank weapons, especially at close quarters, where the Sturmpanzer IV was expected to engage.

To address this weakness, some vehicles received supplementary armor plating affixed to the lower section. This extra armor aimed to obstruct incoming shots from penetrating the vulnerable area after being deflected by the angled bow plate.

On each side of the upper structure, there were closable MP 40 sub-machine gun or pistol ports for close-quarters defense.

The rear of the upper structure featured two escape/entry hatches, and two open-top boxes were added to house the ventilation system for the fighting compartments. Mounted on the back of these boxes were the two antenna sockets.

Additionally, substantial accessory and tool boxes were affixed to the vehicle’s right side. Moreover, extra road wheel mounts were added to the rear of the engine compartment.

Maybach HL 120 TRM on test in a workshop <a href="<a href="" rel="nofollow"> Source</a>
Maybach HL 120 TRM on test in a workshop Source

The Maybach HL 120 TRM Engine

The vehicle drew its power from a solitary Maybach HL 120 TRM series 12-cylinder engine, boasting a robust 300 horsepower output.

This gasoline engine, designed by Maybach AG and produced by Maybach and other licensed manufacturers, was a common fixture in several German tanks and half-tracks both before and during World War II. Before the mid-1930s, German military vehicle manufacturers had the freedom to select power plants from various engine suppliers. However, by October 1935, the design and production of nearly all tank and half-track engines had been centralized within a single entity, Maybach AG, located in Friedrichshafen on Lake Constance.

The vehicle’s range with this engine was limited to just 130 miles, which somewhat constrained the Sturmpanzer IV’s overall strategic utility.

Production line of Sturmpanzer IV Heavy Assault Gun<a href="<a href="" rel="nofollow"> Source</a>
Production line of the Heavy Assault Gun Source

Production of Sturmpanzer IV Heavy Assault Gun

Production of the vehicle commenced in April 1943. In that month, the Nibelungen plant at St. Valentin converted 20 units from reconstructed or repaired vehicles, followed by an additional 32 in May. The upper structures were crafted by Eisenwerke Oberdonau and Böhler at Kapfenberg.

The Austrian companies Saurer and Simmering-Graz-Pauker oversaw the overall production program.

Following the initial series, Bismarckhütte took over the production of the superstructures of Sturmpanzer Brummbär.

In total, 368 vehicles were manufactured by Deutschen Eisenwerke and Nibelungenwerke, with chassis numbers ranging from 80801 to 84400, 86601 to 87100, and 89101.

Production came to a halt in March 1945, almost at the end of the war, resulting in a total of 306 new and 62 reconstructed vehicles overall the Second World War.

Early version of Sdkfz 166 Stupa <a href="<a href="" rel="nofollow"> Source</a>
Early version of Sdkfz 166 Stupa Source

First versions

Production of the initial batch of 60 vehicles commenced in April 1943. Out of these, 52 were assembled using brand-new Panzer IV Ausf. G chassis, while the remaining 8 were constructed by refurbishing Ausf. E and F frame. Approximately half of these units underwent a rebuilding process that commenced in December 1943, primarily aligning them with the specifications of the second series.

The original 60 production models were based on Panzer IV E and G variants. Notably, the original PIV/E base remained unaltered, retaining its partial armor on the chassis sides and the extended exhaust pipes. While the upper structure was removed, no modifications were made to the engine covering.

These early versions required a crew of four but lacked any form of self-defense capabilities, such as the 7.92mm defensive machine guns present in later production models.

The Updated Brummbar Version

Production resumed in December 1943 with an additional 60 vehicles, exclusively utilizing new Ausf. H base, and this continued until March 1944. The Sturmpanzer’s first taste of combat in the Battle of Kursk highlighted a vulnerability in its lightly armored driver’s compartment, prompting reinforcement measures.

To enhance crew comfort, the gunner’s hatch was removed, and a ventilator fan was installed. An attempt was made to reduce stress on the front suspension by replacing the front two rubber-rimmed road wheels with internally sprung, steel-rimmed ones, although this was only partially successful.

The most significant change involved the introduction of all-steel road wheels. The number of these wheels varied between individual vehicles, ranging from the front pair to all eight wheels per side. Some vehicles in this series featured a new exhaust system with two protruding pipes.

While the upper structure remained largely unchanged, alterations were made to the driver’s compartment. The driver’s visor was replaced with an angled mirror system, reminiscent of late Panzer V production. Rain protection plates were added above some mirrors.

Furthermore, the gun mantlet received additional armor, and a ventilator was installed in front of the loader’s hatch, while the two rear ventilators were removed. Only one antenna socket was installed instead of the previous two.

Additionally, the loader’s hatch was removed, and the tool boxes were relocated to the right side of the vehicle.

Late version of Sturmpanzer IV Brummbar stuck in the swamp, left by the crew in 1945<a href="" rel="nofollow"> Source</a>
Late version stuck in the swamp, left by the crew in 1945 Source

Late versions

In early 1944, a redesign of the superstructure was implemented, incorporating the base and HL120 TRM112 engine from the Ausf. J model. This redesigned version of the vehicle entered production from June 1944 to March 1945.

Among the notable changes were a revamped gun collar and a general reduction in the superstructure’s height. A machine gun was fitted to a ball mount in the front of the superstructure to accommodate an MG 34 gun with a 600-round capacity.

Additionally, modifications were made to the vehicle commander’s position, utilizing the cupola from the Sturmgeschütz III Ausf. G, which could be fitted with a machine gun for anti-aircraft defense.

Deployment and Combat History of the Assault Gun

On April 19th, 1943, an order was issued mandating the establishment of a Sturmpanzer Abteilung by May 20th, 1943. The initial war strength report, known as Kriegsstärkenachweis (K.St.N.) No. 1150, initially specified a staff company comprising two command tanks.

According to K.St.N 1175, dated November 1st, 1941, each of the three combat companies was tasked with deploying 13 Sdkfz 166 Sturmpanzer IV vehicles. However, following the recognition of their special status by Hitler, new K.St.N. reports were issued, namely No. 1156, 1160, and 1164.

Initially, the staff company was intended to field 3 Panzer III command tanks, but this plan was later revised to include 3 Brummbär vehicles instead. Each company was structured to include 3 platoons, each consisting of 4 Brummbär vehicles, with an additional 2 for the company commander and his second-in-command.

Despite the K.St.N. specifying the use of Panzer III command vehicles, they were never actually provided to any of the established formations, even as the war progressed. Therefore, the intended strength of a Brummbär Abteilung ultimately amounted to 45 Sturmpanzer IV vehicles.

Sturmpanzer IVs of the Sturmpanzer-Abteilung 216 during Operation Citadel in 1943 <a href="<a href="" rel="nofollow"> Source</a>
Sturmpanzer IVs of the Sturmpanzer-Abteilung 216 during Operation Citadel in 1943 Source

Sturmpanzer-Abteilung 216

The inaugural combat deployment of the Sturmpanzer took place with Stu.Pz.Abt. 216, which was established in late April 1943. Shortly after its formation, the unit relocated to Amiens in early May for training on the new assault vehicles. The division was structured into three line companies, each comprising 14 vehicles, along with a battalion headquarters boasting three vehicles.

On June 10, 1943, it arrived in Central Russia, preparing for Operation Citadel (Unternehmen Zitadelle), the German offensive against the Kursk salient. For this mission, it was temporarily attached as the third battalion of schweres Panzerjäger Regiment 656 (“Heavy Anti-tank Regiment 656”), operating under the 9th Army within Army Group Center’s command.

Staying in the Orel-Bryansk region, it underwent a transition to the Dnepropetrovsk-Zaporozhe area by the end of August. There, the vehicles were refitted, and the unit remained until the Zaporozhe Bridgehead was abandoned on October 15.

The battalion executed a retreat to Nikopol, actively participating in the defense of the German salient in that area until it was eventually withdrawn back to the Reich by the end of December.

Sturmpanzer IV on the Nettuno - Anzio front in Italy, February 1944. <a href="" rel="nofollow"> Source</a>
Sturmpanzer IV on the Nettuno – Anzio front in Italy, February 1944. Source

The Allied landing at Anzio on January 22, 1944, led to the battalion regaining its independence and being transferred there in early February, this time with 28 vehicles. Its purpose was to partake in the planned counterattack against the Allied beachhead, known as Operation Fischfang.

Although this operation failed to achieve its objectives, the battalion continued its presence in Italy for the remainder of the war. By the time of the Po Valley offensive in April 1945, the battalion still possessed 42 vehicles. However, to prevent capture or due to losses during the retreat, all these vehicles were destroyed before the war came to an end in May.

Destroyed Sturmpanzer IV related to Sturmpanzer-Abteilung 217<a href="<a href="" rel="nofollow"> Source</a>
Destroyed Brummbar related to Abteilung 217 Source

Sturmpanzer-Abteilung 217

Stu.Pz.Abt. 217 came into existence on April 20, 1944, at the Grafenwöhr Training Area. It was initially formed using personnel from Panzer-Kompanie 40 and Panzer-Ersatz Abteilung 18. However, it lacked any armored fighting vehicles until the end of May when 19 Sturmpanzers were finally delivered.

The unit departed for the Normandy Front between July 1 and 2 but had to detrain in Condé sur Noireau, which was about 170 kilometers (110 miles) behind the front lines. This detour was necessary due to extensive damage inflicted on the French rail network by the attacking forces.

During the road march towards the front lines, many of the battalion’s vehicles experienced breakdowns. The first recorded combat deployment of Sturmpanzers from the unit was on August 7, near Caen. By August 19, the battalion had 17 operational Sturmpanzers, with an additional 14 undergoing maintenance. Most of the battalion avoided being trapped in the Falaise Pocket and managed to retreat northeastward.

By October, the unit’s strength dwindled to just 22 vehicles, which were divided between the 1st and 2nd Companies. The surplus crew members were reassigned to Panzer-Ersatz Abteilung 18.

The battalion participated in the Battle of the Bulge but only advanced as far as St. Vith. For the remainder of the war, it found itself continuously retreating and was eventually captured in the Ruhr Pocket in April 1945.

Sturmpanzer-Kompanie z.b.V. 218 during Warsaw Uprising 1944 <a href="<a href="" rel="nofollow"> Source</a>
Sturmpanzer-Kompanie z.b.V. 218 during Warsaw Uprising 1944 Source

Sturmpanzer-Kompanie z.b.V. 218 and 2./218

In August 1944, Sturmpanzer-Kompanie z.b.V. 218 was established and deployed to Warsaw, where it became part of Panzer Abteilung (Fkl) 302. Following the suppression of the Warsaw Uprising, it continued its service on the Eastern Front until it was ultimately eliminated in East Prussia in April 1945.

Initially intended to serve as the core for Sturmpanzer-Abteilung 218 in January 1945, it was never withdrawn from the front lines for this purpose.

Simultaneously, Sturmpanzer-Kompanie z.b.V. 2./218 was also formed, but it was dispatched to the Paris region on August 20th. Although its activities in France are not well-documented, its personnel were later assigned to Panzer-Ersatz Abteilung 18 at the year’s end, with the intention of incorporating them into the establishment of Stu.Pz.Abt. 218.

It was officially ordered to be formed on January 6, 1945, initially consisting of three companies equipped with a total of 45 Sturmpanzers. However, during February, it received Sturmgeschütz III assault guns instead of the initially planned Sturmpanzers.

Destroyed armor of Sturmpanzer-Abteilung 219 in 1945 <a href="<a href="" rel="nofollow"> Source</a>
Destroyed armor of Sturmpanzer-Abteilung 219 in 1945 Source

Sturmpanzer-Abteilung 219

Originally intended to be formed from Sturmgeschütz-Brigade 914, Stu.Pz.Abt. 219 underwent a change in plans, as it was instead associated with Sturmgeschütz-Brigade 237 in September 1944. By mid-September 1944, the brigade relocated to the Döllersheim Training Area for the purpose of reorganization and re-equipping.

With merely ten Sturmpanzers in their possession, the battalion received orders on October 15th to partake in Unternehmen Panzerfaust, the German operation aimed at preventing Hungary’s surrender to the Allies. All these vehicles were allocated to the First Company, which promptly set out for Budapest on the following day. However, due to bomb damage to the rail network, its arrival was delayed until October 19th, by which time it was no longer necessary, as a pro-German government had already been established.

Subsequently, the battalion was transported by rail to St. Martin, Slovakia, for further training. It was later redeployed to the vicinity of Stuhlweissenburg to provide relief to besieged German forces in Budapest.

The battalion remained in the Budapest area until it was compelled to retreat due to the advancing Soviet forces until the end of the war and was captured.

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