Sturmgeschütz IIIG Development

Guderian’s opposition to the assault gun had eroded with experience. Not only was its frontline utility indisputable, it could be manufactured faster and in larger numbers by less experienced enterprises than the more complex turreted tanks. Guderian correspondingly advocated restoring the panzer regiments’ third battalions and giving them assault guns as a working compromise.

The vehicles he intended were significantly different from the original assault guns and their underlying concept. The mission of supporting infantry attacks had become secondary at best. What was now vital was holding off Soviet armor. The self-propelled Marders, with their light armor and open tops, were well into the zone of dangerous obsolescence. In 1943 the Weapons Office ordered the development of a smaller vehicle mounting a scaled-down 75mm gun on the chassis of the old reliable 38(t). The 16-ton Hetzer (Baiter) was useful and economical, and continues to delight armor buffs and modelers. It was, however, intended for the infantry’s antitank battalions, and did not appear in combat until 1944—one more example of diffused effort that characterized the Reich’s war effort.

On the other hand, the Sturmgeschütz IIIG, with its 75mm L/48 gun, seemed highly suited to tank destruction and was readily available—until Allied bombing intervened. The factory manufacturing the bulk of IIIGs was heavily damaged in late 1943. To compensate, Hitler ordered the available hulls to be fitted to Panzer IV chassis. The result proved practical enough to encourage the production of over 1700 Jagdpanzer IVs by November 1944, despite Guderian’s protest at the corresponding fallout of turreted tanks. The new name of “tank destroyer” suited the vehicles’ new purpose, though their predecessors continued in service under the original title, creating confusion during and after the war that remains exacerbated by the vehicles’ close resemblance.

Panzer III Development

The Panzer III represented half of that future. Its design orders were first issued in 1935, and for security purposes it was initially designated “platoon commander’s vehicle.” The first four prototypes, offered by four different firms, were tested in late 1936. The winner was Daimler-Benz, but the contract proved a mixed blessing. The original specifications were for a tank weighing 15 tons and capable of 25 miles per hour. Daimler made the weight by limiting the armor to Panzer II levels, and adapted a suspension system from its civilian vehicles that restricted the speed to 20 miles per hour. The result was more tinkering. A reworked suspension and a more powerful engine improved the speed even when the armor was increased to as much as 30mm, offering reasonable protection against large fragments from artillery shells and glancing hits from antitank rounds. The design’s final weight was 19.5 tons—still well below the 24 tons that were the limit of German field bridges.

All this took time. The Panzer III went through no fewer than four type designations before the Model E was considered sufficiently refined to manufacture in some numbers. Even then the first general-production version of the tank was one letter later. The Mark F went into production in September 1939—just too late for the Polish campaign.

Replacing the panzers’ material losses was not a simple one-for-one process. The workhorse Panzer III was increasingly outclassed by its Soviet opponents—less from any qualitative improvement than because the Russians were beginning to learn how best to take tactical advantage in particular of the T-34’s powerful gun and high maneuverability. The Panzer III’s chassis was too light, its turret ring too small, to be a useful transition to the next panzer generation. They were issued as stopgaps, and by mid-1943 appeared in no more than company strength.

The Panzer IV, in contrast, had a future. Improved muzzle braking enabled it to carry the 43-caliber Tank Gun KwK 40, and a more powerful 48-caliber version introduced in late 1942. More than 1,700 of these F and G models were produced or upgraded before they gave way in March 1943 to the definitive late-war Panzer IVH. Its armor was significantly increased: 80mm on the front and 50mm on the turret, 30mm on the sides and 20mm in the rear—the latter reflecting Red Army infantrymen and antitank crews’ willingness to come to close quarters for a kill. The additional protection increased weight to 25 tons and reduced speed to 21 miles per hour, but the Model H could still move and maneuver well enough. Its 75mm, 48-caliber gun was roughly equivalent to the T-34’s main armament, and effective against almost anything it could reach.

The Panzer IVH/J integrated a useful set of upgrades into a state-of-the-art light medium tank, intended to equip one battalion in each panzer division. More than 3,000 would be built in 1943, and more than 3,100 in the war’s final 18 months. They were nevertheless regarded as stopgaps, holding the line for a new generation of exponentially more powerful armored fighting vehicles.

Early StuG IIIG models

The Ausf G was the last production series of the StuG. RoIling off the assembly-line in December 1942, the Ausf G was produced until the end of the war, with no major design changes. In 1942, the decision was made to use Pz Kpfw III Fgst for StuG production, since the Pz Kpfw III was being phased out and replaced by the Panther. In response to this request, 165 Pz Kpfw III Ausf M Fgst were used as chassis for StuG Ausf G, with production from February to November 1943. In 1944, 173 Pz Kpfw III, returned to the factory for overhaul, were converted to StuG Ausf G. 

 StuG III Ausf. G (Sd.Kfz. 142/1; December 1942– April 1945, ~8423 produced, 142 built on Panzer III Ausf. M chassis, 173 converted from Panzer III): The final and by far the most common of the StuG series. Upper superstructure was widened: welded boxes on either sides were abandoned. This new superstructure design increased its height to 2160 mm. Backside wall of the fighting compartment got straightened, and ventilation fan on top of the superstructure was relocated to the back of fighting compartment. From March 1943, driver's periscope was abandoned. In February 1943 Alkett was joined by MIAG as second manufacturer. From May 1943, side hull spaced armour plates (Schürzen) were fitted to G models for added armour protection, particularly against Russian anti-tank rifles, but were also useful against hollow-charge ammunition. Side plates were retro-fitted to some Ausf. F/8 models, as they were be fitted to all front line StuGs and other tanks by June 1943 in preparation for the battle of Kursk. Mountings for the side plates proved inadequately strong as many were lost in the field. From March 1944, improved mounting was introduced, as a result side skirts are seen more often with late model Ausf G. From May 1943, 80 mm thick plates were used for frontal armour instead of two plates of 50 mm + 30 mm. However, a backlog of StuGs with completed 50 mm armour existed. For those, a 30 mm additional armour plate still had to be welded or bolted on, until October 1943.

A rotating cupola with periscopes was added for the commander for Ausf G. However, from September 1943, lack of ball bearings (resulting from USAAF bombing of Schweinfurt) forced cupolas to be welded on. Ball bearings were once again installed from August 1944. Shot deflectors for cupolas were first installed from October 1943 from one factory, to be installed on all StuGs from February 1944. Some vehicles without shot deflectors carried several track pieces wired around the cupola for added protection.

From December 1942, a square machine gun shield for the loader was installed, allowing an MG 34 to be factory installed on a StuG for the first time. F/8 models had machine gun shields retro-fitted from early 1943. The loader's machine gun shield was later replaced by rotating machine gun mount that could be operated by the loader inside the vehicle sighting through a periscope. On April 1944, 27 of them were being field tested on the Eastern front. Favourable reports led to installation of these "remote" machine gun mounts from the summer of 1944.

Later G versions from November 1943, were fitted with the Topfblende pot mantlet (often called Saukopf "Pig's head") gun mantlet without coaxial mount. This cast mantlet with organic shape was more effective at deflecting shots than the original boxy mantlet armour of varying thickness between 45 mm and 50 mm. Lack of large castings meant that the trapezoid-shape mantlet was also produced until the very end. A coaxial machine gun was added first to boxy mantlets from June 1944, and then to cast Topfblende from October 1944, in the middle of "Topfblende" mantlet production. With an addition of a coaxial, all StuGs carried two MG 34 machine guns from fall of 1944. Some previously completed StuGs with boxy mantlet had a coaxial machine gun hole drilled to retrofit a coaxial machine gun, while Topfblende produced from Nov. 1943 - Oct. 1944 without machine gun opening could not be tampered with. Also from Nov.1943, all-metal return rollers of a few different types were used due to lack of rubber supply. Zimmerit anti-magnetic coating to protect vehicles from magnetic mines were used from September 1943-September 1944 only.

Notice that on this gunner's side of the recoil shield there are two black objects and an associated electrical wire. The top one is a signal light and the lower a simple on/off switch. After the loader rams his round into the breech, he pushes his safety switch (on his side of the gun) and this light would glow to indicate to the gunner that the weapon was loaded, locked, and ready to fire. The wire hanging down from the on/off switch leads to an emergency back-up firing device, should the palm switch on the traverse wheel fail to electrically fire the gun.