Monday, 2 July 2018

A Timely Purchase

Soviet trials of the PzIII medium tank, purchased in the summer of 1940, are frequently discussed by military history enthusiasts. The conclusions that various authors make from these trials seem rather mixed. Let us try to figure out the real influence of the study of a PzIII Ausf.G tank purchased at the dawn of war using archive documents.
The result of cooperation

The Red Army's Main Auto and Armour Directorate (GABTU) had nearly no information about the PzIII until the start of WWII. The reason for that was simple. Unlike the PzII and the PzI, German medium tanks were not available in large numbers. Various issues led to the first PzIII tanks being shown at a parade in Berlin only on April 20th, 1938. These were PzIII Ausf.A and PzIII Ausf.B tanks. Both variants, as well as the Ausf.C and Ausf.D that followed were built in very limited numbers.

The vehicle that was to be Germany's main tank was pursued by technical issues, chiefly with the suspension. After Porsche K.G. designed a torsion bar suspension, the Z.W.38 came to be. However, this tank did not go far from the initial concept. However, after a six month delay, the Z.W.38, later indexed PzIII Ausf.E, was put into production. Initially, the numbers were not high, and a rate of more than 20 tanks per month was only reached in August of 1939. In total, only 96 tanks of this type were built. Considering that the PzIII Ausf.D was the most numerous PzIII variant before that with only 30 tanks built, this was already an achievement.

As of September 1st, 1939, the Wehrmacht had only 51 PzIII tanks in its ranks. It's not surprising that nearly nothing was known about it in the USSR.

PzIII Ausf.G NIIBT proving grounds, August 1940

The Red Army first familiarized itself with the PzIII tank in late September of 1939. This happened in Western Ukraine, which was a part of Poland at the time. On September 19th, the Soviet 24th Light Tank Brigade entered Lvov, after which it engaged the German units in the city. The brigade lost a BT-7 tank, and the Germans lost a few anti-tank guns. The fighting quickly stopped. Afterwards, at the end of September, the 24th Light Tank Brigade formed a special group. Its objective was a Polish repair yard at Tomaszów Lubelski. It was known that Polish tanks were there, plus an unknown amount of captured German tanks. A bold raid managed to extract "two German anti-tank guns, 9 Polish tanks, 10 tankettes, and up to 30 cannons".

The same tank from the rear. The smoke grenade launcher can be seen.

Two German tanks were found among the trophies. Incorrect interpretations of this information led to a number of sources claiming that a German PzIII was extracted in this way. This is incorrect. Documents clearly state that no German medium tanks were obtained in the fall of 1939. However, two PzII tanks were obtained, one Ausf.B and one Ausf.C. One of the vehicles was used as a spare parts donor, then shot up.

Purchased in late spring of 1940, the tank was very interesting to Soviet specialists.

However, one PzIII tank was stolen after all. This episode is described in the memoirs of A.V. Yegorov, who served in the 24th Light Tank Brigade. The incident occurred during a visit to a German tank unit quartered in Poland.

"This meeting may not have been memorable if not for one unforeseen event that took place. My subordinate, Senior Lieutenant Tkachenko, displayed "initiative" that I later got an earful about from my superiors.
When after inspecting the tanks, the hosts and guests went to the mansion for a banquet, Tkachenko fell behind. He climbed into a German T-III tank, carefully inspected the controls, and figured out what did what. He tried to start the engine: pressed the starter, increased the fuel supply, and the engine started. He came up with a daring plan: to steal the tank and study it carefully. The Germans told us that this was their newest tank...
The Germans found out about this missing tank on the same day. We received a complaint. Colonel Fotchenkov, the head of our delegation, could not answer anything, and was very surprised when I reported about Tkachenko's actions. He called us both up. As soon as we reported of our arrival, he descended upon the Senior Lieutenant:
"You understand nothing of politics, comrade Tkachenko!" Fotchenkov exclaimed, not attempting to hide his fury. "Your poorly thought out actions could cause serious complications in our relationship with Germany! What were you thinking?"
"I was thinking about my Motherland, our army!" Tkachenko replied.
Fotchenkov was marching up and down the office. He stopped in his tracks. He didn't expect such an answer.
"Get a load of this guy's lofty excuses!" This time he was talking to me. "He was thinking about his Motherland, about our army. Did you think about how our country always precisely respects its agreements and deals with other nations?"
Tkachenko was silent. Perhaps he only now realized the consequences of his action...
"Comrade Colonel, listen to me," the senior lieutenant pleaded. "I am a reconnaissance commander, I thought only to find out information about the vehicles of the enemy."
"Reconnaisance is not done so brashly!" Fotchenkov retorted. "This is not a permitted technique, comrade Tkachenko."
"In battle this information would cost tens, maybe hundreds of lives," the senior lieutenant tried to reason. "I tried to preserve those lives..."
The conversation ended with a formal reprimand for me and Tkachenko, as well as immediate orders to retrieve the tank and return it to the Germans."
Of course, it would not have been possible to study the tank in such a short period of time. However, in the fall of 1939 a diagram of a German medium tank with its approximate characteristics and weak points was composed. The diagram showed a PzIII Ausf.D. It is likely that Senior Lieutenant Tkachenko stole this type of tank.

The same tank from the right, antenna raised.

Full scale study began only in the summer of 1940. By that point, mutual cooperation was set up between Germany and the USSR. The Germans purchased raw materials, the USSR purchased tools. Nearly 6500 German tools were received, which came in very handy later. The inverse of the popular quote "the German sword was forged in the USSR" was true: the Soviet sword was forged using German tools.

In addition, the USSR obtained German armament and vehicles. This included German Sd.Kfz.7, Sd.Kfz.8, and Sd.Kfz.9 halftracks. 3 samples of each were purchased. Finally, a tank was bought, a PzIII Ausf.G. This was one of the last PzIII tanks armed with a 37 mm gun. As of July of 1940, the PzIII Ausf.G was built with a 50 mm KwK 39 L/42 gun. The Soviet military did not know about this. Either way, the purchase of a German tank was very fortunate.

Upsetting the balance

Study of the tank began immediately upon its delivery to the USSR. The vehicle was delivered to the NIBT proving grounds in Kubinka in early June of 1940, along with the halftracks. On June 10th, a plan of inspection was composed. In addition to members of the General Staff and People's Commissariat of Defense, the document mentioned engineers from leading tank factories. Various components of the PzIII were disassembled for study. A fairly detailed album with technical descriptions was composed by September 4th, 1940. 

Photograph showing the driver's observation device. These observation devices were installed on early models of the PzIII.

A large white spot follows in the history of this PzIII. It is known that mobility trials were held, but no report is present at the RGVA (Russian State Military Archive) and RGAE (Russian State Economics Archive). One can confidently say that the Soviet testers rejected the German air filter. Because it worked so poorly, it was taken off the tank and replaced with a domestic one. During the war, captured tanks that were repaired, as well as the SG-122 and SU-76I were immediately equipped with Soviet air filters.

The tank travelled for 800 km during mobility trials.

The dual MG-34 mount is visible. The Germans got rid of it in the summer of 1940.

Since the report is missing, one can only make some assumptions based on other available information, specifically the characteristics that the NIBT proving grounds prepared about its tanks. The most interesting item is the top speed of 69.7 kph. Many debates raged about this number. In reality, the tank could indeed accelerate up to this speed. The Z.W.38 was designed as a combat vehicle with very high mobility. The tank, equipped with a Maybach Variorex 328 145, could attain the top speed of 67.07 kph in tenth gear. Considering errors on the speedometer and the road conditions, 69.7 kph could indeed be a realistic figure. Either way, the table of technical characteristics of foreign tanks composed on March 7th, 1941, states this as the tank's maximum speed.

Characteristics of foreign tanks, March 1941. The PzIII's top speed is 70 kph.

Further actions of the GABTU in relation to the SP, and the future T-50 tank, and modernized T-34 also confirm these findings. The initial concept of the SP (aka T-126) was of a tank with a top speed of 30 kph, later 35. This was the speed that the T-26 could attain. But the T-135, later T-50, had different requirements: 50 kph. The prototype T-50 could go even faster, 52 kph. The Kirov factory prototype was even faster than that, at 64 kph. This speed has a direct cause. In some documents, the T-50 is directly compared with the PzIII.

In the T-34 modernization project dated January 1941, the top speed is given as 65-70 kph. A 600 hp V-2K engine would be installed to provide that speed. However, the factory admitted that this sort of speed was impossible. The draft requirements for the A-43 tank examined in April of 1941 state the stop speed of 60 kph for the tank with 45 mm of armour and 55 kph for the tank with 60 mm of armour.

Driver's combat observation device.

As you can see, the speed of the German tank was an unpleasant surprise for the GABTU. However, there was one caveat that came with that speed. Heinrich Kniepkamp would have smirked if he ever found out about the noise that was raised around this German tank. The problem was that the PzIII could not drive for long at that speed. At speeds over 40 kph, the road wheel rims started to layer and peel off after a short time. The speed was limited to 40 kph as a result. Starting with the PzIII Ausf.H, the 6-speed ZF SSG 77 synchronized gearbox limited the tank's speed to 42 kph, even though the NIBT proving grounds managed to accelerate a captured tank to 50 kph.

The observation devices were interesting to Soviet engineers.

The top speed was not the only feature of the tank that influenced Soviet tank design. After trials at Kubinka, the PzIII went on tour through Soviet tank factories. Some Russian historians claim that Soviet tanks were copies of the PzIII, but let's leave those claims on their conscience. Not a single clone was built in the USSR. Individual components were either copied or creatively reworked, however. About the same thing happened in Germany a year later, when the study of a captured T-34 forced the Germans to make significant changes to their plans. Neither case involved direct clones. Both tank building schools developed in their own way.

The turret direction indicator was later copied on the T-50.

Leningrad factories were the first to get acquainted with the German tank. The tank was carefully inspected by staff of the Kirov factory, Izhora factory, and factory #174. After that, it was partially disassembled. One spare track link, a torsion bar, and a road wheel were kept as samples. The observation devices, aforementioned components that were removed, turret traverse mechanism, and other minor components were considered interesting. Factory #174 composed diagrams of nearly every component. Samples were taken from the hull for study, and oil was drained for study as well. 

The MG mount itself was not very interesting, but the idea of a dual MG was used on the T-50.

The influence of the German tank on the Kirov factory was minimal. KV family tanks received commander's cupolas. It was first used on the T-150, but the design was nothing like the German cupola. The Soviet cupola was meant only for observation and did not have a hatch in the middle.

The influence of the German tank on another vehicle, the T-50, was much more noticeable. Aside from the increased requirement for top speed, some German elements migrated onto the vehicle. The most noticeable was the commander's cupola, which was also different from the German variant. The turret also received a dedicated commander's station. The idea of a dual machinegun mount was also borrowed. The military liked this idea, since it improved the density of fire. However, that is where the influence ended. The Kirov T-50 was largely an original tank that was already fully formed before the German tank arrived at the factory.

Smoke grenade launcher.

The theory that the T-50 was a copy of the German tank holds no water. The SP program began back in February of 1940, and the full scale T-126 model was presented on July 9th. The tank already took its shape by then. As for the parts borrowed from the PzIII, they are listed in the report prepared by the T-50's chief designer, S.A. Ginzburg, on April 10th, 1941.

"In response to your letter #144353 sent on January 27th, 1941, I report that the experience from the T-III tank was used in the following components of the T-50:
Position of crew and armament in the turret
Like on the T-III tank, the commander of the T-50 is located in the rear of the vehicle, behind the brass catcher. To allow for 360 degree vision, a commander's cupola is installed on the turret, 240 mm tall, equipped with seven (either on the pilot batch) observation prisms, unlike the vision blocks on the T-III, which noticeably increases the commander's safety.
Like on the T-III tank, the T-50's 45 mm gun has two coaxial machineguns. In order to reduce the size of the turret front and increase the protection offered by the armour, the T-50, unlike the T-III, cannot independently aim the cannon and its machineguns.
In addition, the T-50 uses the following T-III-style devices:
  1. Three-colour light indicators for commander-driver communication.
  2. Gun position indicator.
  3. Portable lamp with an electromagnet.
  4. Individual elements of the ammunition and tool racks.
As for the transmission, even though it was very interesting, neither the layout nor the individual components could be used on the T-50. Unlike the T-III, the T-50 has a rear transmission.
Nearly all designers, testers, and researchers were familiar with the T-III. A number of components, such as the spare gearbox and spare shock absorber, were completely taken apart and diagrams were drawn. A number of components were photographed.

A number of engine elements were used when designing the new engine at our factory."
Tales about a significant number of parts copied from the PzIII when building the T-50 are exaggerations.  The A-43 (T-34M) received even less from this tank. It was thoroughly studied at factory #183 when it arrived in December of 1940. Specialists took samples from the torsion bars, suspension arms, track pins, and armour. The engine, suspension, transmission, armament, and observation devices were taken apart and studied. Drawings of the more interesting elements and parts were made. Of course, the study of the German tank came in handy when designing the A-43, but aside from the addition of a cupola and a third turret crewman nothing else was used. The torsion bar suspension for the T-34 was proposed long before the German tank appeared, and its design was different. As for the running gear of the first A-43 variant, it was closer to the T-50 running gear than that of the PzIII.


The same tank at the NIBT Proving Grounds in September of 1941. The number 37 indicates the caliber of the gun.

In March of 1941, as a result of demands by the Stalingrad Tractor Factory, the German tank was sent to Stalingrad. On June 20th, by the demand of the chief of the proving grounds, it was returned to Kubinka. The vehicle stayed there until the evacuation to Kazan. Its brief characteristics made it into the reference book composed in September of 1941. To make the vehicle look more "authentic", German crosses were painted on it. Later, the tank's trail vanishes. Perhaps, it was sent to Kazan and then used to repair the PzIII Ausf.H that was tested in the winter and summer of 1942.

A trick with the armour

In addition to Leningrad tank factories, the PzIII was studied at the Izhora factory. This was the leading Soviet organization in the field of armour study. Later, the Armour Institute, or NII-48, was formed from it. The tale of how the tank's armour went through trials should be told separately, since a rather creative retelling of the trials has very little in common with reality. According to this legend, a tank allegedly captured in Poland was shot at in the spring of 1940. Allegedly, the results caused panic, since the armour was only penetrated 2 of 5 times.

In reality, the trials that were held in the fall of 1940 were with a hull and turret of the PzII Ausf.B. Firing at the right side with a 37 mm gun showed that German armour was brittle, but the welding seams were deemed good.

The right escape hatch that was studied at the Izhora factory.

The PzIII Ausf.G arrived at the Izhora plant in September of 1940. Of course, the hull was not shot up, since only one was available. The first order of business was to measure the plates, take samples from the sides and front, and determine hardness using the Poldi method. Later, specialists performed a chemical analysis, but since the samples were contaminated by a large amount of carbon in the steel, the data was deemed approximate. Conclusions were made that German armour was made from high-carbon steel. The hardness was deemed normal for this kind of armour.

Unlike the common misconception, the thickness of the plates was measured correctly: 30 and 20 mm. The sides of the turret and hull were made from homogeneous armour, and the front from heterogeneous.

Half of the hatch before firing.

Later, permission was obtained from the GABTU to extract one component for study and firing. The evacuation hatch door was chosen for samples. The component was replaced with an identical one produced by the Izhora factory. The Kirov factory cut the extracted part in half. One half stayed at the factory, the other was given to Izhora. It turned out that the hatch made made from high carbon steel that was different from the type used in main armour and hull plates.

The result of the trials. The plate shattered after the first hit with a 45 mm shell.

Firing trials were held to determine the robustness of the armour. The shell used was a 53-BR-240 blunt tipped shell at a range equal to the limit of penetration for a 30 mm plate (velocity of 533.8 m/s). The result of the trials was unexpected. The first hit shattered the plate into 8 pieces. Later, the plate was shot at with the 12.7 mm DK machinegun. It turned out that the limit of penetration was 150 meters. There was a suspicion that this behaviour came from the size of the part or the thermal effect of cutting. To confirm this, the Izhora factory produced an identical component from Soviet FD 5634 armour steel. It was first cut in half and then shot at the limit of penetration (525.4 m/s, then 564.2 m/s). The shells did not penetrate, and only two bumps formed. The problem was clearly not with size or the thermal effect.

The result of firing at the same component made from Soviet steel.

The Izhora factory considered this result incomplete, since the other parts of the tank were made from different steel. However, trials of the rest of the hull were not possible at the time.

Panic about "bad shells" mentioned by some authors was noticeably absent in late 1940 and early 1941. In October of 1940, trials of the 45 mm anti-tank gun mod. 1937 showed that it could penetrate 30 mm of armour at an angle of 30 degrees from 1000 meters. The worry was caused by 40 mm plates, which could only be penetrated from 150 meters. Insufficient robustness of shells was indeed noted, but it was only critical when firing at plates 40 mm thick and higher.

The insufficient penetration was already known, which was one of the reasons work on the 57 mm ZIS-2 began. As for 30 mm plates, they were penetrated without problems at long range. Data from later trials also confirms this. For instance, when firing on the side of the StuG III Ausf.B with a 53-BR-240 shell produced in 1938, the T-70 penetrated its side from 850 meters. The same result was observed when firing on other 30 mm plates. Issues only arose when firing at thicker armour, but this was not news for the Soviets.

9 comments:

  1. I was wondering if the demand for duel coax Machine Guns originated with the large scale use of Pz. 1's which used two guns because they employed MG-13's. I can't imaging how in 1940 at the time the Wehrmacht was desperately short of MG-34's for it's infantry that they would seriously consider using two side by side pointing in the same exact direction in their tanks.

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  2. This is actually a late Panzer III Ausf. E or F, not a G model. Some sources said that two Panzer III (3,7 cm) Ausf. E were sold to Soviet Union.

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  3. Honestly, I find it interesting that the armor was deemed brittle, something which I would have thought would only really start showing up in late-war machines.

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    1. Probably related to the German economy kind of having tanked by the late Thirties due to cockeyed Nazi policies. Having access to the world market isn't all that useful when your currency effectively has no value abroad and you have to conduct your trade with bilateral barter deals.

      Not sure who controlled the major sources of alloying elements at the time but chances are good many of them weren't finding it in their interests to sell such strategic materials to an increasingly threatening troublemaker either. (Compare the US cutting oil sales to Japan over the Chinese war.)

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    2. I have a document up with an order to cut nickel from helmets in 1940, so the issues with alloys started coming up a lot earlier than the end of the war.

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    3. German tank production was expanding and it's difficult to keep making thicker and thicker armor plates. And despite everything else we should not discount the possibility that Germany did give away a tank with inferior armor.

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    4. I have also read comments about the quality of late war German helmets, but I thought it had more to do with working surface. In later models they were "trimmed" to save material.

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  4. Ausführung G? As in Hamlet becoming Gamlet is Russian? ;)

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