Sunday, 22 January 2017

Pz.Kpfw.IV Ausf. D through E

The German army entered WWII with a rather strange system of armament. The PzIII medium tank, which was built as Germany's main tank, ended up being the least numerous in the Wehrmacht. As for the other medium tank, the PzIV, it was designed as a support tank, but ended up outnumbering the PzIII four to one. German industry could only equalize the number of both tanks by the end of 1939. By then, a new version of the support tank was in production, the PzIV Ausf. D, which was in a way a return to the original concept.

The Hull Machinegun Returns

The spring of 1938 was rocky for the PzIV. The 6th Waffenprüfamt wanted to get rid of Krupp's tank from the production lineup. A proposal was made to built a support tank on the PzIII chassis, joining both medium tanks into one.

On one hand, the idea was solid. However, the PzIII wasn't doing so well at the moment, but production of the PzIV went on, if not without hiccups. Krupp's engineers also managed to meet the weight requirements on the first try.

When Erich Wolfert, Krupp's chief engineer, criticized the idea of uniting both tank into one, he was victorious. The 6th Waffenprüfamt had to retreat, since Wolfert was supported not only by the arms giant, but by common sense.

However, the lesson wasn't learned, and the 6th Waffenprüfamt would struggle with the idea of one chassis for two types of tanks for the entire war. This obsession, initiated by Heinrich Ernst Kniepkamp, among others, hit the same walls every time. Seemingly, no lessons were learned.

PzIV Ausf. D in its initial configuration. The tank would look slightly different built in metal.

Meanwhile, the requirements for a support tank kept growing. In early January of 1938, discussions of a fourth modification of the tank began, indexed 4.Serie/B.W.

One of the first requirements was the return of the hull machinegun. Someone in charge finally understood that it's hard to shoot out of a pistol port, let alone hit something. A decision was made to use the Kugelblende 30 ball mount designed for the Z.W.38 (future PzIII Ausf. E). It was much better protected than the ball mount on the PzIV Ausf. A. Due to the return of the hull machinegun, the characteristic step of the turret platform front returned.

Diagram of the inside of the tank.

A meeting was held in Berlin on March 10th, 1938, where Krupp employees and representatives of the 6th Waffenprüfamt discussed the possibility of improving the tank's armour. The sides of the hull, turret platform, and turret were only 14.5 mm thick. It had to be 20 mm thick to protect it from 20 mm cannons at long ranges. In addition, the military wanted the floor to be 10 mm thick, up from 8 mm.

The answer to the new requirements came on April 12th. According to calculations, this thicker armour would increase the tank's mass by 1256 kg to almost 20 tons. Further changes to other elements of the hull followed. The maintenance hatches around the return rollers changed shape, as did the air intakes for the engine compartment. Track links with bigger teeth were designed in late April, and the amount of travel stops for the suspension was increased to five per side (one for each of the front three bogeys, two for the rearmost one).

Mass production PzIV Ausf. D, spring 1940.

Changes were made to the turret as well. First of all, the armour of the gun was changed. The design in use earlier was vulnerable to enemy fire. Bullets or shrapnel that hit in the opening between plates could jam the weapon. The development of new gun armour began in late May of 1938. The new gun mantlet was external, and did its job much better than the old. Its thickness was increased to 35 mm.

The observation ports on the side hatches and sides of the turret were replaced.

A large amount of spare track links hanging off the tank was a common sight.

By the time the contract for 4.Serie/B.W. was signed with Krupp on July 4th, 1938, the vehicle changed noticeably. According to the contract, Grusonwerk, one of Krupp's factories, was supposed to build 200 tanks of this type.

The contract was expanded in October. The SS ordered 48 tanks, indexed 5.Serie/B.W. These tanks weren't any different from the 4.Serie/B.W. These tanks, however, never made it into the SS, as a decision to order StuGs instead was made.

Tanks from the 4th and 5th series received the index PzIV Ausf. D. The tanks received serial numbers in the 80501–80748 range.

Experience from Two Campaigns

Mass production of the PzIV Ausf. D began in October of 1939. Unlike the PzIII, whose production was rushed, there were no bursts in the production of the support tank. 45 tanks were assembled by the end of 1939, and further production was 20-25 tanks a month on average. 129 tanks of this modification were delivered by May 1st, 1940.

Torn off turrets were a common occurrence for the PzIV Ausf. D. France, May 1940.

In March of 1939, it was decided that the Wehrmacht would keep buying these tanks, and tanks from the 6th series would be indexed PzIV Ausf. E. A new contract for 223 tanks of this type was signed in July of 1939. Overall, this tank was supposed to be the same as its predecessor, but some changes began to appear in May.

For starters, the driver's observation device, which hasn't changed since the PzIV Ausf. B, was replaced with the Fahrersehklappe 30. Instead of massive parts that traveled up and down, this device had a 30 mm thick protective shield that could be lowered. It was much better at protecting the observation device, and its design was simpler.

The large ventilation hatch on the roof of the turret disappeared, and a fan was added in its place. A hatch for signal flags replaced the periscopic observation device. The commander's cupola changed shape.

PzIV Ausf. D, April 1940 production, with armour added to the front of the turret platform and the middle front plate.

It became clear that the Ausf. E would not enter production in its current shape and that the Ausf. D needs changes after the Polish campaign of 1939. The problem was that the Poles actively used the Armata przeciwpancerna 37 mm wz. 36 Bofors gun against German tanks. Even though Polish shells weren't of the best quality, they could confidently penetrate German tanks from any angle. Even thickening the front plate to 30 mm didn't help.

An investigation began in the fall of 1939 to determine if it was possible to further load the PzIV with armour, increasing its mass to 21.4 tons. Trials showed that the tank could take it.

The 6th Waffenprüfamt made changes to the 4.Serie/B.W. and 5.Serie/B.W. order on December 18th, 1939. The last 68 tanks were supposed to have hulls with 50 mm of front armour. However, by the start of the French campaign on May 10th, 1940, the PzIV Ausf. D was still produced with 30 mm of front armour.

PzIV Ausf. E from the 20th Tank Division, summer 1941.

The first battles showed that this delay was a mistake. Of course, short barreled 37 mm guns used by a number of French tanks, such as the FCM 36 and Renault R 35, could not penetrate this armour, but they weren't the main opponent of German tanks. The French had good anti-tank artillery, and 30 mm was not a problem for it. Even worse, a number of French tanks carried 47 mm guns.

Losses of PzIV tanks were even worse than in Poland. Out of 279 PzIV tanks present on May 10th, 97, or a third, were lost irreparably. The fighting in May-June showed that the short 75 mm gun is powerless against tanks with shell-proof armour.

It was clear that the issue had to be solved, and fast. Krupp reported that applique armour for the hull and turret platform was produced and tested. The front of the turret platform received an additional 30 mm of armour, raising the overall thickness to 60 mm. The sides were reinforced with another 20 mm of armour. Later, extra armour for the front plate was added, along with carriers on the top and bottom.

The army did not receive a single set of applique armour before the end of the campaign. Supplies started on June 25th, by which point they were no longer needed. Widespread equipment of tanks with added armour began in July. The thickness of the front plate, turret front, and gun mantlet was increased to 50 mm.

Not all PzIV Ausf. E received applique armour.

Another serious modification to the PzIV Ausf. D was made in August of 1940. According to a decision made on June 3rd, the last 68 tanks of 4 and 5.Serie/B.W. would be built with 6.Serie/B.W. turrets and turret platforms. The last vehicles of this type were delivered to the army in October of 1940, after which the PzIV Ausf. E entered production.

Tanks of this type received serial numbers 80801–81006. They can be differentiated from the last 68 PzIV Ausf. D only by serial number. Additional mix-ups were caused by the fact that not all PzIV Ausf. E, not to mention Ausf. D, received applique armour on the front of the turret platform.

PzIV Ausf. D with additional Vorpanzer armour, 1942.

Some tank units attempted to make their own tank armour in early 1941, but orders from the top told them to stop. Nevertheless, another modification known as Vorpanzer appeared. It featured massive applique armour on the front of the turret. PzIV Ausf. D, E, and F tanks were modified in this way. It appears that Vorpanzer tanks were used exclusively by the Großdeutschland tank division. There are claims that these tanks were only used for training, but front line photographs discredit the idea.

For Crossings and Other Purposes

The full volume of 4th, 5th, and 6th series was never completed. Some of the PzIV Ausf. D tanks were used for other purposes. 16 March-April 1940 production tanks were used to make Brückenleger IV b bridgelayers. These vehicles were included in engineering battalions attached to tank divisions. They were used by units who fought in France in May-June of 1940.

Brückenleger IV b. A batch of 16 such vehicles was made in the spring of 1940.

Meanwhile, Krupp built 16 sets of turret platforms and turrets. Later, tanks with numbers 80685, 80686 and 80687 were converted into regular PzIV Ausf D. According to report for May 1941, 13 of 29 PzIVs built were from 4.Serie/B.W. 247 Ausf. D vehicles were used by the military as ordinary tanks. The last tank, 80625 , was used as a test chassis.

Brückenleger IV from the 39th Tank Engineering Battalion, 1941.

The situation with the PzIV Ausf. E was different. Instead of 223 tanks that were to be built initially, 206 were finished, 200 of them as tanks. 4 6.Serie/B.W. chassis were sent to Magirus where they were used to make Brückenleger IV c bridgelayers. Like bridgelayers of earlier series, they were sent to the 39th Tank Engineering Battalion and participated in fighting on the Eastern Front in the summer of 1941. 

Pz.Kpfw.IV Ausf.E 81005 and 81006 had a new suspension.

The fate of the last two tanks of the 6th series, 81005 and 81006, was even more interesting. On December 14th, 1940, the 6th Waffenprüfamt allowed Krupp to develop a new suspension. Its main feature was that the diameter of the road wheels grew to 700 mm, and they had to be interleaved to fit. The width of the track links increased to 422 mm. These tanks were tested actively in 1941-42, after which tank 81005 turned up in the training facility at Wünsdorf. At least one tank was converted to an ammunition carrier for the Karl Gerat 040.

Tauchpanzer IV from the 18th Tank Division.

Finally, a portion of the mass production tanks were converted to rather interesting vehicles. 48 PzIV Ausf. D tanks were converted into Tauchpanzer IV to cross rivers along their floor. Special waterproof tarps were added to the tank, as well as covers for the air intakes. A hose with a buoy was used to supply air to the tank. A small amount of PzIV Ausf. E tanks from the January-March 1940 production were also converted. These tanks were used in June of 1941 in the 18th Tank Division.

In Support of Blitzkrieg

Production of the 7.Serie/B.W., or PzIV Ausf. F, began in April of 1941. This tank was made with experience from the first two years of the war, but it only became the army's main support tank in the fall of 1941. They were a minority of the 441 PzIV concentrated at the Soviet border on June 22nd, 1941. The majority of them were PzIV Ausf. D and E.

By then, tanks of these modifications began to look differently. On February 14th, 1941, the first German tanks arrived at Tripoli, and the Afrika Corps was formed on the 16th. In connection with this, a "tropical" modification for the ventilation system was developed.

In March, a container for personal items was added to the back of the turret. Since it was originally designed for the Afrika Corps, it earned the nickname "Rommel box". It wasn't used on all tanks. On some tanks, it was not installed on the turret, but on the side of the hull. Some units designed their own "Rommel box", whose shape was different from the original.

This was just the start of all possible modifications that were introduced at the division, and sometimes battalion level. The equipment of a PzIV for 1941 alone is a topic worthy of its own sizeable article.

PzIVs in Africa were in their element. 20 tanks were sent in February, 3 of which were lost on the way, and 20 more arrived in April. The only seriously dangerous enemy of the PzIV was the Matilda tank, due to its thick armour. However, the 2-pdr (40 mm) cannons of these tanks could only penetrate the applique front of the PzIV at close range, and these situations were rare.

The result of a PzIV meeting a KV-2, summer 1941.

The conditions of the Eastern Front were different. Only 15 PzIVs were irreparably lost until the end of June, mostly because their enemies were T-26 and BT tanks from a completely different weight class. The chaos of the first few weeks of the war also left its mark. However, 109 tanks, a quarter of the initial amount, were scrap by the end of July. 68 more joined them in August. In total, the Germans lost 348 PzIVs in 1941, over three quarters of their initial amount.

German tankers could squarely point the blame at the 6th Waffenprüfamt, which treated the issue of armour very lightly. The tanks were up-armoured according to experience from September of 1939. The fact that the French had 47 mm L/32 tank and anti-tank guns which, as Soviet trials proved, could penetrate 50 mm of German armour from 400 meters, was ignored.

The characteristics of the 47 mm Canon de 47 Mle.1937, which had a length of 50 calibers, were even more distressing. It could penetrate 57 mm of armour from a kilometer away. The Germans should have assumed that the French weren't the only ones who had more powerful anti-tank artillery than the Poles.

PzIV Ausf. E from the 20th Tank Division, NIIBT proving grounds, August 1941.

The Wehrmacht had to pay with tanks and men for the miscalculation of their leadership. Things went well enough while the main opponents were T-26 and BT tanks, but T-34 and KV-1 tanks armed with 76 mm guns appeared more and more frequently. Some tanks were also only partially up-armoured, which reduced the chances of survival under fire from even 45 mm guns.

The KV-2 also made an appearance. A hit from a 152 mm shell turned the German tank into a heap of scrap. Of course, a penetration from any other shell also had grave consequences. Ammunition detonation was a common occurrence for the PzIV. It's worth noting that the PzIV was powerless against the T-34 and KV-1. Stock armour piercing shells had almost no effect, and Hitler did not allow the use of  7.5 cm Gr.Patr.38 Kw.K. HEAT shells, available in April of 1941, until February of 1942.

The same tank from the front. You can see impacts and the cracked applique armour around the driver's vision port.

In August of 1941, a captured PzIV Ausf. E tank from the 20th Tank Division was delivered to the NIIBT proving grounds at Kubinka. The tank was rather beaten up: there were several hits to the front and the applique armour around the driver's vision port was cracked. Proving grounds employees composed a brief evaluation, estimating the mass of the "Medium Tank T-IV Mod. 1939-40" as 24 tons and its top speed as 50 kph. After preliminary calculations, the following conclusions were made:
  • The armour of the T-IV can be penetrated by artillery of all calibers.
  • The tank's turret, observation hatches, and the radio operator's machinegun mount are vulnerable to high caliber machineguns.
Captured PzIVs became a common occurrence after 1941. Nevertheless, the NIIBT proving grounds didn't attempt to repair the captured tank, nor obtain a functioning specimen.

This is mostly due to the fact that the Soviet military had little interest in the tank. It was treated as an auxiliary to the PzIII, especially since their mass was similar. This is also why the StuG III Ausf. B was not put into working order. Study of the PzIII and Pz38(t) took priority, and it was considered pointless to waste time on secondary tanks. 

Unlike the StuG III, the PzIV's armour was vulnerable to the 45 mm gun.

Trials were held in September of 1942 where the tank was subjected to shots from various guns. First, it was fired at by the DShK machinegun. The side of the turret was not penetrated even at 50 meters, but the side and rear of the hull could be penetrated at 100 meters.

The results of trials against the 45 mm gun were even more interesting. The 50 mm front plate could be penetrated at 50 meters. It's worth noting that the same gun could not penetrate a captured StuG's front. The 40 mm (20+20) thick side armour was penetrated from a distance of 400 meters.

Finally, the PzIV was pitted against the 76 mm F-34 gun installed in the T-34 medium tank. The front plate was penetrated from 500 meters (entrance diameter of the breach was 90 mm, exit diameter 100 mm). The next shot from 800 meters cracked the plate in half. Firing from 800 meters at the side of the tank, she shell penetrated the side armour, blew up inside, and penetrated the other side. An HE shell fired at the side of the tank tore off the turret hatch, the second shot tore off the commander's cupola, and a hit to the engine compartment (20 mm armour) formed a 130x350 mm breach. No more shots were fired, the situation was already clear.

In addition to shooting at the tank, NII-48 specialists performed an analysis of the hull and turret design.

One of the PzIV Ausf. D tanks that was armed with a 7.5 cm KwK 40 cannon and equipped with spaced armour.

The few remaining PzIV Ausf. D and E tanks were modernized in July of 1942. Instead of the stock gun, they were equipped with the long barreled 7.5 cm KwK 40. Starting in May of 1943, spaced armour was added to the hull and turret. By that point, these tanks were taken off the front lines and handed over to training units, including the NSKK.

These tanks were present in tank units located in France. One of them (PzIV Ausf. D, serial number 80732, produced in July of 1940) was captured by the British in the summer of 1944. Today, it can be seen at the Bovington Tank Museum.


  1. What is "Waffenampt"? Such a word does not exist in german or english. I suppose You mean WaPrüf6, instead. That translates into Waffenprüfamt 6 (amt without -p)

    The tank subjected to shooting trial wass burned out. Any ballistic trials are meaningless therefore due to secondary heat treatment.

    1. Your valuable input is appreciated, as always.

    2. I like that tone of vague insinuations without actually committing to anything.

  2. I was very suprised to see that the Soviets used burned out tanks for firing trials. Burned out vehicles were declared as irrecoverable because the exposure to heat followed by slow air cooling is the hallmark of temper embrittlement, changing the steel to a different crystalline condition, and significantly reducing the impact toughness and ductility of the armor plate. Even if burned out vehicles were restored to working condition, the armor did not offered the same level of resitence as before.
    I have always thought that the soviets may have lacked the fundamental knowledge of heat treatment steel alloy dependent embrittlement ranges by studying the metallurgy of their projectiles (some of which have the least desirable heat treatment imaginable: soft and brittle) but this case gives a very direct evidence for this preumption.
    To restore the original condition of the armor plate of a burned out tank would require complete annealing and reheat treatment to the specifications.

    1. So let me get this straight... you're trying to claim that the engineers of a major heavy-industrial nation, who cheerfully engaged in extravagant shenanigans like this when working on their alloys, were ignorant of something that was fairly well understood by *Medieval* metalworkers and very much an exact science by the late 1800s?


    2. From what I see is that if the tank was burnt out it was only the rear part of the tank. I am looking at the side were the back 5 road wheels lost their rubber. Maybe burnt off? The three front ones look fine as well as the return jacks. So a fire may not have had any affect on the front armor of the tank.

      As to why the 45mm gun did better on the tank than the StuG is the lower front hull of a StuG was 50mm @ 20° while the PZ IV was 50mm @ 15°.

    3. Mobius,

      Steel is a good heat conductor, not the best one but that´s why we can cook in steel pans. Unless You erect an asbestos barrier between the origin of the fire and all steel plates, the temperature will buildt up from plate to plate, inside the plates -expanding from the centre through the section- even at considerable distance from the origin of fire. When the area of the heat affected steel reaches the plate surface, surface oxydation sets in, which appreciably changes the colour tone as is visible in the scorching of the frontal plates. But it´s "too late" already much earlier.

      The difference of 15° to 20° obliquity is a not a substantial factor for AP ammunition in general (safe only old ww1 vintage naval soft capped AP which have their working boundary in this obliquity range) and soviet AP ammunition in particular. It will deform always striking cal/thick plates, leaving a blunt nose or-more likely- a broken nose. Penetration through the plate thus is not effected by piercing but by punching out a plug of armor, requiring a different penetration mechanism. Plugging is particularely sensitive to changes in the plates impact strength, which in turn is the most negatively affected aspects of secondary heat treatment caused by burned out steel.
      These penetration mechanics have a relatively flat change in velocity in the range of 0° up to 30/40° obliquity compared to projectiles which stay intact, which is sometimes mistakenly interpreted as evidence for a superior obliquity performance when in fact it represents only that the penetration is "capped" -at a significantly lower level.
      Pz III 30mm + 30mm frontal plate wasn´t penetrated either and the combined effect of laminated plates is hardly more than 53mm.
      To expect penetration of an intact 50mm frontal plate is possible but requires either the projectile to perform well above specifications or the plate to perform well below specification.

  3. Mobius,
    the front plate down from the nose plate and up to the driver plate is showing scorching. Material from this tank would not be tolerated as test armor by either US, german or british standarts.

    You seem to underestimate the complexity of temper britellness. For some alloy conditions, solutions were not found until the 1970´s. Mistakes in heat treatment of armor plate were made by all sides during ww2 to varying degrees.
    Soviet Russia was very recently industrialized by massive help from abroad, and Silicon manganese steels were nothing new or "extravagant" but already 30 years old when the soviets started to experiment with them.
    And yes, we have evidence from metallurgical studies of soviet ww2 ordnance products that they payed no attention to temper britellness or, alternatively, if they indeed realized it, they did not care about it´s effects and did not even try to remedy the problem. If they considered burned out tanks as suitable ballistic test samples, how can You even think they understood the problem?

    1. I was not referring to the material, but the paces it was put through. *OBVIOUSLY*.

      As far as munitions go I'd hazard a guess quality control problems related to the massive production volumes involved and the often rather ad-hoc industrial conditions might of have been relevant. I mean I've read of some pretty hilarious manufacturing cock-ups in other contexts stemming from the exact same reasons.
      Those shells still seem to have killed an awful lot of German tanks though so "good enough for governement work" I guess...

      Why they used burnouts as test targets I couldn't rightly say. Maybe just a lack of more intact specimen? This was after all the phase of the war when the Germans were still usually gaining ground and recovering their salvageables...

      And it's not like the conclusions are exactly wrong anyway, whatever the shape of the test subject.

    2. They shot up a hull they had lying about. Did you miss the part where Soviet specialists didn't care about the PzIV enough to obtain a functional one? This wasn't done because, as you imagine, they were primitive Asiatics that didn't understand fire.

    3. No need to become ironic, Peter. I do not buy into national, ethical or racial thumb chesting.

    4. This comment has been removed by the author.

  4. Lack of fundamental understanding of heat treatment is not just manifest in soviet ammunition, also gun tube and breech materials, welds and armor plate have plenty of evidence for it. Ammunition is only the best known case because the track record of these failures extend from ww2 into the period after Korea. Considering that the Soviets and the germans both used AP(BC)HE or APC(BC)HE ammunition, the ability to repair most of the damaged german A.F.V. speaks volumes to the lack of effectivity of soviet ammunition. There are also good materials among soviet ordnance items, particularely moderate thickness, high hardness silicon manganese plates. But the items are inconsistent in quality indicating either a lack of quality controll or a lack of process skill. Sometimes the alloy content is high enough to allow for full hardenability but the heat treatment is so poor that only parts of the sections are hardened and only incompletely so with other areas beeing both, soft and brittle. A mindless waste of critical alloys. As if one would have applied the heat treatment which worked at a specific section thickness for a specific alloy condition uncritically to thinner or thicker sections, alike. The same issue reoccur with ammunition, which -taken together with other evidence like the use of burned out tanks as ballitic targets- points very strongly towards a lack of fundamental heat treatment knowledge.
    As I mentioned previously, the test result is worthless as it was directed against secondary heat affected plate. It´s worse even, that the soviets issued the result of this trial as part of their service fighting instructions, as You won´t see a burned out Pz IV engaging in firefights.

    1. Do you feel the need to keep doing this thing where you'll write 259 different comments of a paragraph each about how everything that Peter posts is a communist lie? If you don't like him you could just go away, you know.