Gepanzerte Selbstfahrlafette fur Sturmgeschütz 7.5 cm Kanone Ausführung A/B (Sturmgeschütz III Ausf.A/B Hybrid)

German Reich (1940)
Self-Propelled Assault Gun – 6 to 20 Built

The early StuG IIIs were plagued with production delays, resulting in its late introduction to service. In May 1940, two more units equipped with StuG IIIs were to be formed. As the promised vehicles were instead transferred to SS forces, new vehicles had to be delivered in order to fully equip them. Given the production of new vehicles was temporarily delayed, the Germans simply reused what they had on hand, creating hybrid vehicles that incorporated parts from the Ausf.A and Ausf.B series, but also used an unmodified Panzer III chassis.

The First StuG IIIs Enter Service

The importance of having vehicles such as the Sturmgeschütz (English: Assault gun) was mainly heralded by Erich von Manstein. He argued for the introduction of a highly mobile, well-protected, and well-armed self-propelled artillery gun. Such vehicles were meant to provide infantry with mobile close-fire support during combat operations. Thanks to the self-propelled chassis, these could be quickly redeployed to respond to any new threat. Towed artillery, on the other hand, was often vulnerable to enemy return fire and needed time to change positions. This self-propelled artillery gun was to be an organic part of standard infantry divisions.
The Oberbefehlshaber des Heeres (German Commander in Chief of the Army) finally approved the project in 1935. The Waffenamt (English: Ordnance bureau) issued a production order for 280 vehicles. This included 30 vehicles of the initially marked 0-series (actually the Ausf.A version) and 250 of the second series. Due to many reasons, but mostly related to the rather underdeveloped German arms industry, production of the Ausf.A version actually began at the end of 1939. All 30 vehicles were finally completed by April 1940.
From March 1940, these vehicles were designated as Gepanzerte Selbstfahrlafette fur Sturmgeschütz 7.5 cm Kanone, which can be translated as armored self-propelled chassis for 7.5 cm armed assault gun. It is generally best known under the much shorter StuG III name. The first series of this vehicle received the Ausfuhrung (Eng. version or series) A designation.
Given the rather limited production run, it was only possible to equip a limited number of small combat units. The initial unit organization for StuG IIIs was quite simple, as it was limited by the available numbers. Six vehicles were used to form a sturmartillerie batterie (Eng. assault gun battery). These were divided into three zuge (Eng. platoons), each equipped with only two vehicles.
Prior to the start of a Western campaign in May 1940, the 24 available StuGs were distributed to four batteries: the 640th, 659th, 660th, and 665th. The remaining 6 StuG III Ausf.As were used to create an SS assault battery for the LSSAH (Leibstandarte SS Adolf Hitler) Regiment. These were to be attached to various infantry divisions, depending on the combat needs.

Why Build a Hybrid?

As the Ausf.A had a fairly small production run of only 30 vehicles, it was not possible to equip units such as the 666th and 667th batteries. An additional 6 to 20 vehicles were built using different components, such as the Panzer III Ausf.F or G hull and the superstructure taken from the StuG III Ausf.B. The front transmission unit was taken from the StuG III Ausf.A. The secondary literature disagrees as to why the Germans decided to do so and there are a few different explanations.
Author of Sturmgeschütz and its Variants, Walter J. Spielberger, mentions no explanation had been found in the German documentation to explain why these vehicles were built up to the time of publication.
Authors T.L. Jentz and H.L. Doyle (Panzer Tracts No.8 Sturmgeschütz) mention that, due to delays in the delivery of new transmissions, the production of the Ausf.B had to be postponed. As a temporary solution, some 20 hybrid Ausf.A/B vehicles were ordered instead. These were allocated to the 666th and 667th batteries.
Lastly, author T. Anderson (Sturmartillerie Spierhead Of the Infantry) gives a different account. According to him, the need for more vehicles arose when the StuG IIIs allocated to the 666th Batterie were instead given to the LSSAH. The 666th Batterie was planned to be formed on 20th May and was to reach full combat readiness by 20th June (it actually did so on 13th July 1940). Likely due to political connections, priority was given to SS formations, such as the LSSAH Division instead. The 666th Batterie was informed that its six StuG III vehicles were to be delivered by the end of June.
Based on this information, it can be assumed that the simple reason why these hybrids were built was out of a need to form additional batteries. The availability of guns and superstructures was not a problem. The delivery of new transmissions, on the other hand, was problematic. It was the main reason why the StuG III Ausf.B production was delayed. The Germans probably approached this problem with the simplest solution, reusing what they had on hand. Acquisition of a few Panzer III hulls for this project was not difficult, even if the production of the Panzer III was rather slow at this point of the war. As the StuG III used the Panzer III chassis, creating these hybrid vehicles could be done relatively easily. But in general, these hybrid vehicles are rarely mentioned in the sources, and nothing much is known about them.

Name

According to a German war document dated February 1944, this vehicle did not receive any special designation and was known simply as Gepanzerte Selbstfahrlafette fur Sturmgeschütz 7.5 cm Kanone Ausführung A. They received 90401 to 90500 chassis number designations. Despite using components from the Ausf.B, the designation Ausf.A was used, mainly due to it being equipped with the older type of transmission. Thus, the name was not changed, mostly due to bureaucracy and to avoid confusion with the allocation of spare parts. To distinguish between these two series, this article will refer to it as StuG III Ausf.A/B for the sake of simplicity, even though this was not an official designation.

How Many Were Produced?

Production numbers for this vehicle range between 6 to 20. Authors Walter J. Spielberger, T.L. Jentz, and H.L. Doyle mention a number of 20 vehicles being built. T. Anderson initially mentions that 6 vehicles were to be allocated to the 666th Battery. Nevertheless, later on, he cited sources such as P. Müller (Historyfacts), who argued that, based on German production documents and statistics, it is likely that 20 such vehicles were produced. Based on the evidence, the larger number of 20 seems more plausible. The firm responsible for producing these 20 Ausf.A/B vehicles was Daimler-Benz.

Design

This vehicle was quite similar to the Ausf.A, although there are some unique features that help distinguish the two.

Hull

The StuG III Ausf.A/B hull generally had the same design as other WWII German vehicles and can be divided into three major sections. These were the forward-mounted transmission, central crew compartment, and rear engine compartment. The front hull was where the transmission and steering systems were placed and it was protected with an angled armor plate.
The first difference between the Ausf.A and the Ausf.A/B hull, which was taken from the Panzer III Ausf.F and G, was in the front of the hull. The hybrid StuG III used different square-shaped, two-part hatch brake inspection doors, which were located on the front hull. In the case of the Ausf.A/B, these would be opened horizontally and not vertically, as was the case on the standard StuG III vehicles. In addition, the Ausf.A/B also was provided with two armored ventilation ports located on top of the front hull armor plates. Their purpose was to provide cooled air to the front-mounted steering brakes.

Suspension and Running Gear

The StuG III Ausf.A/B used the standard Panzer III suspension, which consisted of six road wheels on each side. These were suspended using a combination of individual swing axles together with torsion bars, which were placed in the bottom of the hull. The upper movement of each wheel’s swingarm was limited by contact blocks covered in rubber. Additionally, the first and the last wheels were equipped with a hydraulic shock absorber. At the front, there was a 360 mm wide 21-tooth drive sprocket. On the back of the hull was the idler with an adjustable crank arm. The number of return rollers was three per side.
The major difference was that the older and unnecessarily complex (prone to malfunctions and breakdowns) 10-speed SRG 32 8 145 transmissions were replaced with a much simpler and reliable 6-speed ZF SSG 77 type. In addition, StuG III Ausf.A/B had two (one on each side) emergency escape hatches located on the lower hull sides. These were located behind the first idler.

Engine

The power unit was the same twelve-cylinder, water-cooled Maybach HL 120 TRM engine giving 265 hp @ 2,600 rpm. This engine was placed at the rear of the hull and was separated from the central crew compartment by a firewall. The firewall had a small door. Its purpose was to provide the crew members with access to the engine if needed.
The engine was held in place by three rubber bushings. With this power unit, the StuG III Ausf.A/B’s maximum speed was 40 km/h, while the cross-country speed was 20 km/h. The fuel load of 310 liters was stored in two fuel tanks placed below the radiators in the engine compartment. With this fuel load, the operational range was 160 km on roads and 100 km cross-country. To avoid any accidental fires, these fuel tanks were protected by firewalls. One minor change was the introduction of a cast cover for the external crank starter port.

Superstructure

The overall superstructure design was left unchanged. It was taken from the Ausf.B, which compared to the Ausf.A, received a slightly modified gunner’s periscope hatch design. One minor difference that the Ausf.A/B vehicle had was the lack of a driver bullet splash deflector, which would be normally located in front of his vision port. The reason for this was the hull hatch design, which opened differently on this vehicle and prevented the installation of this deflector.

Armor Protection

The StuG III Ausf.A/B was constructed using the early Panzer III chassis, which was only protected by 30 mm of frontal armor. Given that standard StuG III was protected by 50 mm of frontal armor, additional armor plates had to be added in order to reach this level of protection. To this end, an additional 20 mm of armor was bolted to the lower front hull armor. The upper glacis appears not to have received the extra 20 mm of armor, which is a bit unusual.
Sources disagree on the effectiveness of this bolted armor plate. Authors F. Kurowski and G. Tornau (Sturmgeschütz – Die Panzer der Infanterie) mention that the Germans made a mistake during the drilling of the holes for the bolts. Namely, the holes were drilled straight instead of being tapered. The consequence of this alleged mistake was that the 20 mm plate was not well connected with the hull armor and thus offered less protection. In addition, if the vehicle was hit in this area, there was a chance of metal splinter ricocheting inside the vehicle, possibly wounding, or, in a worst-case scenario, killing a crew member. This was reported by some of the crews, who criticized this mistake. It must be noted that there is no mention of this flaw in any of the German war documents regarding the use of these vehicles. Besides that, while it complicates the production of new vehicles a bit, no major issue was noted with this kind of armor arrangement. Due to a lack of proper information, the full truth can never be known for sure, but there may have been some issue with this armor, as these vehicles appear to have seen limited service. Because of this, it is possible to assume that some mistakes were made during its construction.

Other than that, the remaining armor was the same, with the hull’s sides and rear being 30 mm thick. The front superstructure armor plates were 50 mm thick. Like the hull armor, the superstructure side and rear were also 30 mm thick. The angled-spaced armor was 9 mm thick and placed at a 30° angle. The top armor was 10 mm, while the top of the engine compartment was slightly thicker, at 16 mm. The gun mantlet was 50 mm thick. The StuG III was one of the most well-armored vehicles in the German arsenal at that time.

Armament

The armament remained unchanged. The main armament consisted of a semi-automatic 7.5 cm StuK 37 (Sturmkanone – assault cannon) L/24. It was primarily designed to engage enemy-fortified positions, but was also equipped to deal with early enemy armor designs. A total of 44 spare rounds were carried inside the vehicle.

Crew

Like in the Ausf.A, the crew of this vehicle consisted of four: the commander, driver, loader, and gunner. The loader was positioned to the right of the gun, with the remaining crew placed opposite. The driver was positioned on the left front side of the hull. Just behind him was the gunner, and right behind him was the commander.

Operational Use and Fate

What precisely happened to the StuG III A/B vehicles is not known. They were delivered too late to participate in the German invasion of the West in May 1940. While at least two batteries received these vehicles, there is little information on their use. What is strange is that these units were mainly photographed using the later Ausf.B vehicles.

Author T. Anderson mentions that one vehicle was lost in combat, but does not provide more details about when this happened, but it was likely in the Soviet Union during 1941. If there was a flaw in the design of the bolted armor plates, there is the possibility that these were removed from service and then reallocated to training units, or even reused in their original configuration. In either case, their final fate remains unknown.

Other Hybrid StuG III

This would not be the last time that the Germans built hybrid StuG III vehicles. Such vehicles were constructed due to production limitations, being repaired with parts that were available onhand or, more commonly, for use as training vehicles.

Conclusion

The StuG III Ausf.A/B was an interesting attempt to produce more StuG III vehicles in a short period of time. Given that very little is known about their performance, a proper conclusion on them would be difficult to make. The fact that only a limited number were made may give an indication that its overall design had some flaws. On the other hand, the production of the later Ausf.B may suggest that such a hybrid vehicle was not needed.

Gepanzerte Selbstfahrlafette fur Sturmgeschütz 7.5 cm Kanone Ausführung A/B Technical specification
Crew	4 (Commander, Gunner, Loader, and Driver)
Weight	20.7 tonnes
Dimensions	Length 5.38 m, Width 2.92 m, Height 1.95 m
Engine	Maybach 120 TRM 265 hp @ 2,000 rpm
Speed
Range	160 km, 100 km (cross-country)
Primary Armament	7.5 cm L/24
Elevation	-10° to +20°
Superstructure armor	front 50 mm, sides 30 mm, rear 30 mm, and top 10-16 mm
Hull armor	front 30+20 mm, sides 30 mm, rear 30 mm, and the top and bottom 15 mm

Sources

D. Doyle (2005). German military Vehicles, Krause Publications.
D. Nešić, (2008), Naoružanje Drugog Svetsko Rata-Nemačka, Beograd
Walter J. Spielberger (1993) Sturmgeschütz and its Variants, Schiffer Publishing Ltd.
T.L. Jentz and H.L. Doyle (1999) Panzer Tracts No.8 Sturmgeschütz
T.L. Jentz and H.L. Doyle (2006) Panzer Tracts No.3-2 Panzerkampfwagen III Ausf. E, F, G, H.
D. Nešić, (2008) Naoružanje Drugog Svetskog Rata-Nemačka, Beograd
P. Chamberlain and H. Doyle (1978) Encyclopedia of German Tanks of World War Two – Revised Edition, Arms and Armor press.
H. Scheibert (1994) Panzer III, Schiffer Publishing
Walter J. Spielberger (2007) Panzer III and its Variants, Schiffer Publishing Ltd.
B. Carruthers (2012) Sturmgeschütze Armored Assault Guns, pen and Sword
M. Healy (2007) Panzerwaffe Volume two,Ian Allan
T. Anderson (2016) Sturmartillerie Spierhead Of the Infantry, Osprey Publishing
K. Sarrazin (1991) Sturmgeschütz III The Short Gun Versions, Schiffer Publishing

https://www.armedconflicts.com/StuG-III-Ausf-A-2-Serie-t191752
https://www.hl-barbara.de/index.php/die-garnison/wehrmacht/sturmartillerie/fotoalbum-batterie-666
https://tanks-encyclopedia.com/stug-iii-ausf-a/