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From Support Tank to a Lead Role

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It often happens that tanks are built for one purpose, but become necessary for another. German tank building is an excellent example of this. The situation with medium tanks was the most complicated. The B.W. tank (Pz.Kpfw.IV) was envisioned as a small batch vehicle, but was several times more numerous than the Z.W. (Pz.Kpfw.III). The situation normalized only by the May-June 1940 campaign, but history repeats itself. By the middle of the war, the Pz.Kpfw.IV once again became the most numerous German tank, outlasting the PzIII in production.

A planned evolution

As with other types of German tanks, the development of the PzIV followed experience in battle. In Poland, it became clear that 30 mm of armour isn't enough anymore. Instead of small caliber autocannons, the Polish brought forth 37 mm anti-tank guns. Penetrating 30 mm of armour was not a problem. 

The conclusions were drawn quickly. The front of the hull and turret platform were thickened to 50 mm. However, German industry was in no hurry. The change was only introduced in the summer of 1940. The front of the hull was indeed thickened to 50 mm, but the front of the turret platform was only reinforced with applique armour due to its complex shape. The driver's station was placed in a protruding cabin, which was done away with on the Ausf.B-C (or rather, the radio operator was moved forward to get rid of the "step" in the front armour). The machinegun was also removed, which was a strange move. The Ausf.D-E regained the "step". Logic dictated that the "step" needs to go, but the machinegun needs to stay. Another issue was that the hull and turret platform were reinforced, but not the turret. Its thickness remained at 30 mm.

One of the first PzIV Ausf.F built at Grusonwerk in the spring of 1941.

A fully fledged increase in protection was only introduced into the next production series. According to the initial plans by In.6, dated December 1938, the 7.Serie/B.W. would only run for 128 units. In November of 1939 this order was enlarged: now In.6 wanted 500 tanks of this type from Krupp (or more precisely, the Grusonwerk factory). In addition to the increased amount of tanks demanded by the war, there was another reason. The PzIV turned out to be the best tank in the September 1939 campaign. Of course, the Armament Directorate still considered the PzIII to be the most necessary tank. Production had only reached the minimally acceptable amounts.

By the start of the fighting in France the PzIII was used by the hundreds. Nevertheless, the idea of creating a unified chassis with different turrets was no longer raised. It was clear that the PzIV had much fewer problems and at least equivalent mobility to the PzIII. All that was needed is the increased protection.

The same tank from the side. It was equipped with the stowage box behind the turret known as "Rommel's box".

The 7.Serie/B.W. (Pz.Kpfw.IV Ausf.F) began to take shape by the start of the summer of 1940. In addition to the thicker front armour, the sides were thickened to 30 mm. The vehicle was protected against the 3.7 cm Pak and analogous guns from the front and low caliber autocannons from the side. The mass of the tank increased, and it was necessary to change the running gear. Primarily, this affected the tracks. Wider Kgs.61/400/120 tracks were installed instead of the old 380 mm wide ones. As before, the track links were compatible with the ones used on the PzIII. The PzIV Ausf.F used a new idler built from tubes. The rubber tires on the road wheels changed from 470x75 mm to 470x90 mm. The diameter of the drive sprockets increased due to the introduction of the new tracks.

The changes to the chassis did not end there. New final drive access hatches with air intakes were introduced. The muffler became noticeably shorter. The auxiliary motor exhaust system changed even more drastically. The large and long muffler was removed in favour of a small box-shaped one.

The turret platform changed once more. The front plate was straightened out and the machinegun ball mount and driver's visor were redesigned.

There were plenty of changes to the turret platform as well. As mentioned above, the stepped shape of the front made it more difficult to protect. The plate was straightened out, which gave the radio operator a lot more room in his compartment. The machinegun ball mount was also changed. Just like on the PzIII Ausf.J, the Kugelblende 50 with a hemispherical armour cover was used. The Fahrersehklappe 50 driver's observation device was installed as well. The number 50 in both cases reflects the thickness of the armour. Due to the changes to this observation device, a new combat driving system with KFF 2 periscopes had to be introduced. The engine deck also changed. Ventilation openings were added to the hatches, the side hatches were changed, and a stock smokescreen system was added to the rear.

The turret was also altered.

The turret also had a number of improvements. For starters, the thickness of the armour was increased. This introduced changes not only to the design of the turret, but also the gun mount. Another change affected the side hatches. Earlier they only had one flap, but on the PzIV Ausf.F they received two. Visors above the hatches were introduced to keep out water. Another piece of equipment was added: the box for the crew's possessions behind the turret, known as "Rommel's box", since the tanks of the Africa Corps were the first to receive them. This box was installed on all German medium tanks starting with the spring of 1941.

Tanks on railroad platforms, 1941. The main changes to the rear part of the tank include the shorter muffler, the smaller auxiliary engine muffler, and smokescreen device.

Preparations for mass production of the PzIV Ausf.F began in June of 1940. By then, the PzIV made a good showing in France, which resulted in an increased demand for this type of vehicle. Knowing that Grusonwerk's abilities were finite, In.6 decided to seek out other ways to increase production. Manufacturers that were already involved in tank production were not considered. Instead, two factories that had never built tanks before were contracted: Vogtländische Maschinenfabrik AG (VOMAG), a manufacturer of trucks and buses from Plauen, and Nibelungenwerk from Saint Valentin, Austria. This factory belonged to Steyr, and was built after the Anschluss to produce tanks. Both factories were only adjusting to wartime footing, and thus the production run was relatively small: 100 tanks of this type from each.

PzIV Ausf.F near Moscow.

The contracts for the PzIV Ausf.E took up resources, and so the predecessor's production run had to be cut short for the PzIV Ausf.F to come in. Nevertheless, the first 13 tanks were delivered in May of 1941, 38 in June, same in July, 42 in August, and 45 tanks per month came out of Grusonwerk after December. The newer manufacturers delayed a bit longer: VOMAG delivered its first two tanks in August of 1941 and reached a monthly output of 12-14 tanks by the end of the year.

Nibelungenwerk was doing much more poorly: the first PzIV was delivered only in November, and two more in December. 470 PzIV Ausf.F were delivered by the end of February of 1942: 393 from Grusonwerk, 64 from VOMAG, and 16 from Nibelungenwerk. Compared to the production of the PzIII this was relatively few tanks, but remember that five factories with extensive experience were building the PzIII Ausf.J.

A tank from the 5th Tank Division captured by the Red Army. NIBT Proving Grounds, 1944.

A late start for the PzIV Ausf.F meant that only a handful of these tanks took part in Operation Barbarossa. These tanks only began arriving on the front lines en masse by the end of the summer and early fall. There were no significant differences between the new tank and the PzIV Ausf.D-E. Of course, the thicker armour was a bonus, but only when dealing with 45 mm guns.

Same tank seen from the front.

As it often happens, the protection did not keep up with the increase in the power of anti-tank guns. The Red Army was already actively using guns 76 mm in caliber and greater, and 50 mm of armour was not enough to save against them. More and more often, the PzIV would see T-34 and KV tanks on the battlefield, against which the 75 mm KwK L/24 was ineffective. 7.5 cm Gr.Patr.38 Kw.K. HEAT ammunition was introduced in late 1941 (officially, February 1942). This round had a high penetration, but was not a cure-all.

The strip of metal along the side of the turret platform was used to keep spare road wheels.

The PzIV Ausf.F did not see significant changes during its production run. However, one change was made almost as soon as production started: a hitch to carry a fuel trailer. In practice, this kind of device did not see a lengthy service, as the trailers were abandoned in the fall of 1941. Another device that was removed was the smoke projector. Its installation stopped towards the end of production, in February of 1942.

PzIV Ausf.F with additional armour, France, 1942-43.

The reinforced armour program known as Vorpanzer should be discussed separately. Discussion of this type of improvement began in July of 1941. Strangely enough, it was experience from North Africa that triggered it, not the Eastern Front. According to German information, the British were using new types of anti-tank artillery that could defeat even tanks with 50 mm of armour. That was not the case, but the Germans designed a countermeasure. A set of applique armour was designed for the PzIV Ausf.E and Ausf.F that covered the front and partially the sides of the tank. This armour was 20 mm thick. It was planned that all tanks of this type would receive this armour starting with spring of 1942, but in practice it was only installed in February of 1942 and was almost never used on the PzIV Ausf.F. There is a photo of a tank of this type with extra armour not just on the front of the turret, but on the turret platform as well, and the design of this armour is similar to the type used on the PzIII Ausf.J-N. Whether or not these tanks were used in battle is an open question.

A more promising platform

Issues with the penetration of the 7.5 cm KwK L/24 became obvious during the French campaign. Considering that protection was gradually increasing, it was obvious that the short-barreled weapon will not remain effective for long, and the issue of improving the firepower was raised. Funnily enough, the Germans proposed a longer 75 mm gun back in the mid-30s, but it was supposed to be installed on a 30 ton tank. As a result of a long brainstorm, the VK 30.01(H) and even the VK 65.01 ended up with the same 7.5 cm KwK L/24. The Germans ended up tricking themselves, and German tankers realized for themselves what a 75 mm gun for a medium tank ought to look like.

PzIV Ausf.F with a dummy 50 mm KwK 39 L/60 gun. The gun in this photo is often mistakenly identified as a tapered bore gun, but that is not the case.

Further development of the situation was no less strange than its start. Hitler interfered with the program, and it's hard to call his decision short sighted. On February 19th, 1941, he gave the order to urgently design a long-barreled version of the 5 cm KwK 38 L/42. Recall that the gun didn't get its "full" 60 caliber barrel, unlike the 5 cm Pak 38. At the time, there was a requirement that a tank gun cannot overhang past the dimensions of the hull. However, there was a desperate need for a longer cannon. The 60 caliber version was to be installed not only on the PzIII, but on the PzIV. As a result, the German army received two different tanks with nearly identical characteristics. One PzIV Ausf.F received a dummy gun. Later, a proper 5 cm KwK 39 L/60 was tested in a PzIV Ausf.D turret.

Diagram of the 7.5 cm KwK 40 L/43.

Another gun was developed in parallel, this one with a caliber of 75 mm. A number of variants were proposed at a meeting on March 12th. One of them had a 40 caliber barrel (the same one that was proposed in the 30s). The penetration at 400 m against a plate sloped at 30 degrees increased from 39 to 70 mm. The muzzle velocity increased from 398 m/s to 670 m/s. Another alternative was a 33 caliber barrel with a muzzle velocity of 580 m/s and penetration of 59 mm.

As a result, the engineers settled on an intermediate variant with a 34.5 caliber barrel. This gun was tested in a PzIV Ausf.F with serial number 82091, but it was not put into production. On November 18th, 1941, the 4th Department of the Armament Directorate initiated the development of a much more powerful gun based on the 7.5 cm Pak 40 anti-tank gun. The length of the rifled barrel was the same as the Pak 40, 2470.5 mm, but the overall length was cut down from 46 to 43 calibers. The length of ammunition was reduced from 969 to 748.3 mm. This had to be done in order to preserve the loader's ability to load the gun and allow the tank to carry an acceptable amount of ammunition. The gun received a single baffle muzzle brake. The gun received the name 7.5 cm KwK 40 L/43. The difference in muzzle velocity was only 30 m/s, and the penetration remained higher than any tank gun before it.

PzIV Ausf.F2. This tank was produced at VOMAG in April of 1942.

The new gun was put into production as soon as possible. It was clear that the single baffle muzzle brake would not last long, and it was soon replaced with a a double baffle one like on the Pak 40. Initially, 30 new guns were expected in March of 1942, 70 in April, 90 in May. In practice, only 18 guns were delivered in March, and VOMAG only delivered one tank with this gun. Initially, the tank was called Pz.Kpfw.IV Ausf.F-Umbau (altered Pz.Kpfw.IV Ausf.F). A new index was introduced on March 21st: PzIV Ausf.F2. The short-barreled version was renamed PzIV Ausf.F1. 104 new guns were delivered in April, 56 in May, 87 in June, 114 in July. This allowed production of the PzIV Ausf.F2 to ramp up: the three factories released 80 tanks in April, 85 in May and 72 in June.

These tanks had next to no changes compared to their predecessors, aside from the gun. Due to the longer barrel, a guard was installed to protect the antenna from damage. Later, a number of PzIV Ausf.F tanks were converted in the field. The amount of ammunition carried increased: thanks to redistributing the ammunition racks, the tank carried 87 rounds of ammunition instead of 80.

A later production model, without observation ports along the sides of the turret. This tank could already be an Ausf.G, despite the single baffle muzzle brake.

The index PzIV Ausf.F2 did not last for long. An order for 1400 tanks of 8.Serie/B.W. heralded a name change. A new index, PzIV Ausf.G, was introduced on June 5th, 1942, and approved on July 1st. The PzIV Ausf.F2 was retroactively renamed to PzIV Ausf.G. This fact confuses many historians and enthusiasts. Additional confusion is caused by the guns. The "classic" Ausf.F2 has a gun with a single baffle muzzle brake, but a number of vehicles received a gun with a double baffle muzzle brake before the name change. Additionally, stocks of old guns still had to be depleted, plus single baffle muzzle brakes remained in production until September of 1942 at the least. A number of tanks called PzIV Ausf.G carried single baffle muzzle brakes.

Another change causing confusion is also connected with the weapon. A gun with a 48 caliber barrel was tested in March of 1942. Thanks to this change, the muzzle velocity of the gun matched the Pak 40 at 820 m/s. The new gun, indexed 7.5 cm KwK 40 L/48, was put into production on August 15th, 1942. However, this did not mean that the 43 caliber gun vanished. The two guns were installed in parallel until April of 1942. For instance, tank 82937 on display at Patriot Park was built in October of 1942, but still had the 43 caliber gun. Earlier 48 caliber guns also had the single baffle muzzle brake, which was only replaced with the double baffle one in September of 1942. In April of 1943, the double baffle muzzle brake changed its form somewhat.

Ammunition rack diagram for long-barreled PzIV tanks.

The new gun shifted the balance of power in the opposition between the PzIII and PzIV. There were plans to install the 7.5 cm KwK 40 L/43 along with the PzIV turret on the PzIII chassis. This version would bear the name PzIII Ausf.K. The problem was that significant improvements to the PzIII chassis were needed to enact this change. The fact that it was not that easy to convert an Ausf.J to an Ausf.K heralded the end of the PzIII. All factories that built the PzIII moved to production of the Panther in early 1943. The issue with that was that the new tank was almost twice as heavy as its predecessor. The role that the PzIII used to play was passed over to the PzIV.

The overall volume of production grew as VOMAG and Nibelungenwerk got used to tank production. The monthly production rate grew to 100 by October, and the three factories delivered 155 tanks in December. 870 PzIV Ausf.G were delivered in 1942 overall, twice as many as all other types of the PzIV by then. The figures from 1942 paled in comparison to next year: production crossed the 200 unit threshold in March and 272 tanks were delivered in May. This became possible to the Nibelungenwerk coming into its groove and delivering 115 tanks in May.

An example of the confusing PzIV Ausf.G. A VOMAG tank produced in September of 1942 still has observation ports on the sides of the turret.

The PzIV Ausf.G turned out to be the most dynamic variant of the tank. In addition to three different guns, other changes and improvements were made, some of which significantly affected the tank's performance and look. One of the biggest changes was the removal of observation ports from the side of the turret and the fright side of the front.

The issue was first raised on January 2nd, 1942, but the ports began vanishing only in April. This does not mean that they disappeared suddenly. The process took until October of 1942. There are photos of tanks that have a single baffle muzzle brake, but no observation ports. Another example is the PzIV with serial number 83072, located in the Munster tank museum (Germany). The tank was produced in September of 1942, but it still has a full set of ports.

A tank produced around the same time without ports.

A more significant change was the reinforcement of the front armour of the hull and turret platform. Experience in 1941 showed that 50 mm was no longer enough. The armour had to be reinforced further. Unlike the PzIII, this was not spaced armour. 30 mm applique plates were welded to the front of the turret platform and hull. This increased the weight of a PzIV Ausf.G to 23.6 tons.

The installation of applique armour was a lengthy enterprise. The first 8 reinforced PzIV Ausf.Gs were ready at Grusonwerk in May of 1942, 16 were delivered in June, July, and August, 14 in September, and up to half of all tanks starting with November. The original plan was to equip all tanks with additional armour starting with July of 1942.

All tanks received extra armour only in January of 1943. A portion of the tanks produced in spring-summer of 1943 had this armour held on by bolts. The thicker armour finally tipped the scales away from the T-34 and in favour of the PzIV. While the 50 mm armour could be penetrated from a kilometer away, the thicker armour was only vulnerable at point-blank range. However, that was just the theory. Applique armour was a much less reliable method of protection than a solid 80 mm plate. The weakened zones of the machinegun ball mount and driver's observation port were still present. The turret front was still only 50 mm thick. It was not possible to make it thicker without overloading the chassis.

The first tanks with reinforced front armour and without observation ports were built in June of 1942. These tanks still had single baffle muzzle brakes.

The stowage also changed. The practice of installing extra stowage that prospered in 1941 was frowned upon, but it was decided to standardize the practice rather than forbid it. The first change was the introduction of the stowage box on the PzIV Ausf.F. A second stage began in June of 1942. A mount for two road wheels was added to the left side of the hull. A holder for seven spare track links was also added to the front of the hull. These changes didn't completely eliminate field conversions, but at least reduced them. 

The instruments that were stored on the fenders changed in August of 1942. The lights were radically changed in September of 1942: the front lights and NOTEK light were replaced with two waterproof Bosch lights. These cylindrical headlights were equipped with flaps that allowed them to be used at night. The rear lights were replaced with one convoy light, also waterproof. To simplify production, the ports from the driver and radio operator hatches were removed. A new simplified guard rail on the barrel was installed starting with November.

A tank with widened Winterketten track links.

A lot of attention was paid to using the tanks in winter. Some thought was given to a "winter package" back in the summer of 1940, but serious work began in the spring of 1942. In addition to a cold weather starter, a snow plow was developed that could be attached to the front tow hooks. The most noticeable addition was the development of winter tracks, "Winterketten". They were wider than regular tracks, which reduced ground pressure. Winterketten were introduced in November of 1942. Little is written about their effectiveness, but there are serious reasons to believe that this feature did not prove itself. The USSR developed extended track links before the war, with poor results. The extended links became bent and broke fairly quickly. Bent German Winterketten come up in archaeological excavations often, suggesting that this issue was never solved.

A tank supplied to Bulgaria. The tank has smoke grenade launchers on the turret and a single piece commander's cupola hatch. Spaced armour is not yet installed.

A significant change was introduced in 1943. A new commander's cupola appeared in February, the biggest feature of which was the use of a one piece hatch, rather than two. Smoke grenade launchers were added to the sides of the turret. They did not last long and were no longer installed as of May 1943. Another change in February of 1943 was the removal of the KFF2 combat driving system.

This tank still has an antenna in the old location.

In April of 1943 another change was made that significantly affected the look of the tank and its characteristics. This change was the addition of skirt armour, which is often referred to as anti-HEAT armour. In reality, this feature was introduced to protect against the PTRD and PTRS anti-tank rifles. Soviet anti-tank rifles, introduced in the fall of 1941, were not particularly effective for frontal fire, but successfully penetrated the sides of German tanks. The skirt armour was developed for this reason. A 10 mm thick horseshoe-shaped piece of armour was attached to the turret, with doors on the sides. Mounts were installed on the hull for 5 mm thick armour. Since this armour was split into 5 sections, it could easily be removed and installed by the crews. Trials held on February 20th, 1943, showed that the anti-tank rifles could penetrate the skirt, but not the main armour.

Hitler gave the order to install the armour on March 6th. They were installed en masse starting in April. In addition, tanks that were produced earlier also received this armour starting with May of 1943. The skirt armour improved the tank's flank protection, but there were issues. The extra armour added 600 kg of weight, and the tank didn't get any lighter. Its mass went up to 25 tons and top speed dropped to 38 kph. The skirts also clipped the ground and obstacles. As a result, it was common to see tanks without this armour. Many only had it installed on the turret.

Additional side armour, a major change introduced in 1943.

The final changes to the PzIV Ausf.G took place in May of 1943. First of all, the antenna port moved from the right side to the rear left of the hull. This allowed the complex folding mechanism to be removed. The guard rail on the gun barrel was also no longer needed, and thus removed as well. New air filters were finally introduced. They were first discussed in August of 1942. It was planned that the air filters would be covered by extra armour, but the solution was much simpler. A port was added to the right side of the hull and two filter bins attached. The filters were introduced in May of 1943, but not to all tanks. Analogous changes were introduced into the very first tanks of the 9th series, named PzIV Ausf.H. These two variants were produced in parallel for some time. The last PzIV Ausf.G was delivered in June of 1943. 1930 were built in total: 907 by Krupp, 430 by VOMAG, 587 by Nibelungenwerk.

One of the last PzIV Ausf.G produced in June of 1943. This tank already has an antenna port in the rear.

The modernization of the PzIV Ausf.G and its further development is lost among the much more popular Tiger and Panther. There are even claims that 1943 was the start of its decline. The production amounts suggest exactly the opposite. The PzIV became the workhorse of the German tank branch and remained in this role until the end of the war. After all of these changes, the tank became a much more dangerous opponent than the PzIII. Its gun could penetrate the T-34 and KV, and not just at close range, but at medium distances. The KV-1 was also replaced in production with the KV-1S, which had thinner armour. Its front could be penetrated by the KwK 40 from 900 m. The PzIV Ausf.G and PzIII Ausf.J-M made up the majority of German tanks at Kursk. The modernized PzIV was a dangerous opponent, with better armament than Soviet tanks and partially better protection. It is not surprising that the production rates of the PzIV only grew. The next two variants became even more numerous, and the PzIV Ausf.J became the most produced tank variant in German history.


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