Friday 20 May 2022

The Necessary Pair

Why the Panther couldn't replace the Pz.Kpfw.IV and why the Germans spent the whole war with two medium tanks.

The German tank building school was among the best in WW2. One could say it finished in second place overall. For instance, the Panther was a very competitive medium tank. The T-34 and Medium Tank M4 had advantages over it in production qualities and modernization potential, but the Panther surpassed them in armour and firepower while maintaining decent mobility. This tank was supposed to become Germany's main tank. It became the most numerous tank in the Germany army by the second half of 1944. Three factories built this tank, putting out 350 units monthly at the peak of production in the summer of 1944. The Panther was also a key part of the future of German tank building. This tank was supposed to be the only medium tank remaining in production by the second half of 1945. It would even be developed further. The Panther Ausf.F with improved frontal protection was supposed to become the main variant.

Three German medium tanks in one shot, July 1943. The Pz.Kpfw.III was on its way out, the Pz.Kpfw.IV was here to stay, and the Panther that couldn't quite replace it.

There is a common misconception that once the Panther appeared on the scene production of other medium tanks either stopped or began to wind down, after which it quickly became Germany's main tank. In reality, peak production of the Panther coincided with peak production of Germany's other medium tank, the Pz.Kpfw.IV. The difference in production volumes was not so great, which is a feat considering that only one factory build Pz.Kpfw.IV tanks starting with the summer of 1944: Nibelungenwerke. Medium SPGs are incomparable, as only the StuG 40 and StuH 42 outnumbered the vehicles built on the Pz.Kpfw.IV chassis, even though it was considered outdated in early 1944. This seems like a paradox, but there were good reasons why the Pz.Kpfw.IV entered production in November of 1937 and stayed there so long and why production of two medium tanks continued throughout the entire war.

In opposition to Kniepkamp

To start, let us explain why Germany ended up with two medium tanks in the fall of 1939. The Germans were not alone in this, although their reasons were special. For instance, by early 1940 the British had three medium tanks in production, but these tanks had different classifications. Pairs such as the Crusader/Covenanter and Centaur/Cromwell came later, but this time they also had different reasons. They were essentially the same type of tank on a different chassis (or sometimes just with a different engine). The French also had their own reasons for having two medium tanks. The Char D2 was designed for the infantry and the SOMUA S 35 was designed for the cavalry. Officially, it was an armoured car and not a tank at all. The Germans arrived in this situation unexpectedly and partially under influence from the British tank building school.

Krupp's Grosstraktor and Leichttraktor were both failures. The USSR received more benefit from these designs than Germany. For instance, the Grosstraktor suspension went straight on the T-28.

Initially, the Reichswehr was supposed to have two tanks: the medium Grosstraktor (16 tons, 75 mm short gun, 40 kph top speed, amphibious capability) and light Kleintraktor (2 crewmen, 37 mm gun, top speed of 40 kph). The latter quickly turned into the Leichttraktor. The mass rapidly increased to 6 tons (and later 8), the crew consisted of 4 men (officially 5, but the turret was too cramped for three). Both of these tanks were failures. The Grosstraktor later evolved into the Nb.Fz. Initial requirements called for a mass of 18 tons, but the resulting vehicle ended up weighing 23 tons. The attempt at building an analogue of the Medium Tank Mk.III was not successful. These "large" tanks were considered the most promising, but things went badly every time. As a result, the situation by the mid-1930s was as follows. The base tank was the Kleintraktor, which turned into the La.S., a light infantry support tank. It was initially supposed to have a crew of 3 and a 20 mm gun, but it was not to be. The La.S. or Pz.Kpfw.I had a crew of two and armament consisting of two MG 13 machine guns. Understanding that something went awry, the Ordnance Department ordered another light tank, the La.S.100. MAN's design turned out to be the best, and so the Pz.Kpfw.II was born. The Germans ended up with two light tanks: a large one and a small one.

Krupp received contracts for Z.W. and B.W. turrets. The second project ended up more than just a turret, as Krupp managed to sell their entire tank.

The situation with medium tanks was equally strange. The Leichttraktor evolved into the Z.W. (Zugführerwagen, or platoon leader's vehicle). This 10 ton tank quickly grew to 12 tons, and the prototypes already weighed 15 tons. As for the Nb.Fz., its fate was sealed in February of 1935. Rheinmetall-Borsig, the tank's creator, received a contract for the verbesserten Nb.Fz. (improved Nb.Fz.) that would essentially be a whole new vehicle. The mass was supposed to be 17-18 tons, but now there was only one main gun: a short 75 mm. The penetration was similar to that of the 3.7 cm KwK, the difference in penetration was not great. This tank was not a main tank. The Z.W. would become the main medium tank, and the role of the verbesserten Nb.Fz. became clear from its new name that was assigned to it in the fall of 1934: B.W. or Begleitwagen (support vehicle). The tank was going to be an artillery tank like the kind the British had in the 20s and the USSR attempted to build in the early 30s. While the UK and USSR built these tanks on existing chassis, Germany built two different tanks with similar characteristics.

The result was a comical situation where the Germans had two medium tanks. The "niche" Pz.Kpfw.IV was clearly better than the "main" Pz.Kpfw.III.

The situation around the "niche" tank remained strange. Krupp won the tender to build the turret, but managed to convince the army that it could build the whole tank. Krupp's design was a surprise. This was the only tank that met the initial mass requirements. It also clearly surpassed its competitor from Rheinmetall, which resulted in signing of a contract for 35 tanks indexed Pz.Kpfw.IV Ausf.A in December of 1936. Grusonwerk delivered its first tanks a year later and obtained a contract for a second series of 42 tanks. This could have been the last production batch. On June 1st, 1937, Krupp received a letter from Heinrich Kniepkamp, the head of tank chassis development in the 6th Department of the Ordnance Directorate. Work on the Z.W.38 a.k.a. Pz.Kpfw.III Ausf.E was underway. Things looked grim for the Pz.Kpfw.III. The first series (A through D) were built in small batches and running gear problems were common. In comparison, the Z.W.38 was built to Krupp's vision of a high speed tank. Its speed was supposed to reach 70 kph, for which the tank needed a brand new running gear with a torsion bar suspension developed by Porsche K.G. It was assumed that the Z.W.38 chassis would be the same for both the future Z.W. and B.W.

At the start of WW2 the Pz.Kpfw.IV was the most numerous German medium tank. They were praised, while the Pz.Kpfw.III received less favourable reviews.

This idea was reasonable, since having two almost identical tanks was indeed far from ideal, but its implementation was faced with some serious hurdles. The saying "if you want to make god laugh, tell him about your plans" is quite applicable in this case. Development of the Z.W.38 dragged on and Krupp began to clash with the 6th Department in the summer of 1937. The Ordnance Directorate sided with him, since they weren't blind. It was clear that Krupp had a working tank while Daimler-Benz did not. The directorate made it clear on June 27th, 1937, that the 2.Serie/B.W. would not be the last order. A contract for 140 Pz.Kpfw.IV Ausf.C (3.Serie/B.W.) was signed in October of 1937. Grusonwerk reliably shipped tanks that did not result in the same headaches that the Pz.Kpfw.III did. These tanks were quite good and both series were delivered by October of 1938. Meanwhile, the Z.W.38 fared poorly. The tank only went to trials in the spring of 1938. It was not immediately successful and had to undergo many changes. This is when Krupp decided to strike. In early May of 1938, Krupp's lead engineer Erich Wolvert asked a series of uncomfortable questions about production of a "universal tank". The result was that the "universal tank" was forgotten, at least for the time being. In July of 1938 Krupp received a contract for a fourth series of 200 Pz.Kpfw.IV Ausf.D tanks. Meanwhile, the Z.W.38 was still being polished. The Pz.Kpfw.III Ausf.E went into production only by the end of the year, spoiling the plans for Germany's "main" tank. The army was supposed to have 2995 tanks of this type by the end of 1940. In reality only 286 tanks were built by the start of the year. Only 98 were available by the start of WW2, of those 87 had been issued. To compare, 147 "niche" Pz.Kpfw.IV tanks were built in 1939. At the start of the war, 211 had been built and 197 issued. Kniepkamp saw no consequences for this failure. Sure, the Tank Commission headed by Ferdinand Porsche was introduced as a counterweight, but he retained his position as the head of chassis design.

In this case the designation "support tank" is almost cynical.

It took a year to make a proper tank out of the Pz.Kpfw.III. 2995 remained an impossible dream. Only 862 were produced in 1940. 290 Pz.Kpfw.IV tanks were built in that same period, but large numbers were not expected for the support tanks. No one paid attention to the fact that this tank was being praised by front line troops. Even foreign powers paid attention to the Pz.Kpfw.III while treating the Pz.Kpfw.IV as a footnote. For instance, the USSR tested the Pz.Kpfw.III, but not the IV. The tank remained an ugly duckling. No one noticed that various improvements required minimal changes to the chassis, while the Pz.Kpfw.III changed dramatically. All attention was focused on Kniepkamp's tank. Vehicles to replace it (VK 20 series) were also on their way, and Kniepkamp had some influence here as well. Krupp also saw some fallout from this. On September 15th, 1939, they began working on the B.W.40, a replacement for the Pz.Kpfw.IV with six road wheels per side 630 mm in diameter with the same bogey suspension. The project was axed on May 16th, 1940. It was later directly suggested that the B.W. was once again under threat. The tank survived, as the only replacement to reach the prototype stage was the VK 20.01 (D). Daimler-Benz disregarded Kniepkamp's opinions and used a diesel engine with a leaf spring suspension. 

In early 1942 it turned out that the Pz.Kpfw.IV tank that was almost killed off not once but twice was the only medium tank that could accept the new 75 mm gun. Until the fall of 1942, the Germans did not fully grasp the problem they created for themselves.

The perilous situation was only truly realized in late 1941-early 1942. First of all, the 20 ton class of vehicles was discarded and the bar was raised to 30 tons (well actually the 30 ton class, as even the initial requirements gave a weight limit of 35 tons). The attempt to build the Pz.Kpfw.III Ausf.K with a Pz.Kpfw.IV turret and a 75 mm KwK 40 L/43 gun failed. The Pz.Kpfw.III's story ended here. Meanwhile, the Pz.Kpfw.IV accepted this gun with no problems. The situation was strange indeed. The tank that Germany tried to get rid of ended up its saviour. However, the VK 30.01/30.02 were expected much earlier than they actually arrived, so the plan was to keep the Pz.Kpfw.III for now. Pz.Kpfw.IV production only ramped up in the fall of 1942. 113 tanks were delivered in November, 155 in December, and then production volumes continued to climb. This is where the design of the tank hit a wall. The modernization reserves of the Pz.Kpfw.IV chassis were depleted by the fall of 1942. Because of this, the front hull of the tank was thickened to 80 mm, but the turret armour remained 50 mm thick. German industry entered 1943 with three medium tanks in production. The Pz.Kpfw.III was living out its last days. The Pz.Kpfw.IV finally rose to the first place, but it ran out of room to grow. Finally, the Panther had just entered production. It was intended to be the main medium tank, but this status still had to be earned.

Over and under

MAN delivered its first four Panther Ausf.D tanks in January of 1943. As mentioned above, this tank surpassed all other medium tanks at the time of its creation. The Panther was no less mobile than the T-34, but surpassed it in front armour and armament. Its economic characteristics we no less impressive. The Pz.Kpfw.IV Ausf.G without armament cost 103,462 Reichsmarks, while the Panther cost 117,100. There were also a lot more Panthers. The relative simplicity allowed production to reach more than 300 units per month as of April 1944. It seemed that the Panther should replace the Pz.Kpfw.IV, since both tanks occupied the same slot. This was no longer a situation with a "main" tank and a "support" tank, but two "main" tanks where one was clearly inferior to the other. However, reality was not that simple. 1777 Panthers and 3072 Pz.Kpfw.IV tanks were delivered in 1943. Any kind of attempt to present the Panther as Germany's only medium tank would have evoked giggling with a German accent. 

Panther V2. Officially, it weighed 35 tons. In reality, clearly more.

This situation seems sudden to the uninitiated. For starters, let's closely examine the Panther tank. It was exceptional, no doubt. The question was: is it what the Germans wanted? Initial requirements called for a 35 ton tank with a power to weight ratio of 20 hp/ton and a top speed of 60 kph. Herr Kniepkamp was still obsessed with his high speed tanks. A 700 hp Maybach HL 230 engine existed, but attempts to iron out its bugs were ongoing since 1937. The height of this engine was 1185 mm (to compare, the V-2 was 1072 mm tall and the Maybach HL 120 just 808 mm). The torsion bars also took up some height. As a result, the VK 30.02 (M) hull was 1377 mm tall, plus a clearance of 500 mm. To compare, the T-34's engine deck stood 1279 mm tall, and the height at the fighting compartment was just 1154 mm. The VK 30.01 (D) that lost the tender was no shorter. Clearly, both tanks weighed much more than 35 tons from the very beginning, and that was before the desire to increase the armour from 60 to 80 mm cropped up. We don't know how much the Panther V2 really weighed, but the production tank weighed 45 tons. The suspension was still designed for a 35 ton tank.

A famous photograph of the first production Panther tanks demonstrated to Speer. What wasn't recorded on this photograph was that 6 out of the 13 tanks broke down.

As a result of all these transformations, the Panther had no modernization reserve. Early tanks were also legendary for their technical problems, the most epic of which happened during the demonstration staged on February 21st, 1943, where 6 out of 13 tanks broke down. Tank factories tried to iron out the bugs between February and April. 324 tanks were all delivered in one go in May, out of which only 200 were sent to Kursk. Enough wondrous stories happened here to full a whole book. Only 7 working tanks were left in the 10th Tank Brigade by July 7th, 1943. Later, the amount of running Panthers oscillated between 25 and 45 vehicles. As a result, the order for 1000 Panther Ausf.D tanks was reduced to 850 and production of the Panther Ausf.A began in July of 1943.

Broken Panthers were a common sight at Kursk.

The Panther had issues to spare. They included road wheels and final drives that broke often, but the biggest cause of headaches was the Maybach HL 230 engine. This engine had a battery of four Solex carburettors. Attempts to polish them lasted all war and never bore fruit. The Maybach HL 234 was supposed to have direct fuel injection for a very good reason. The main feature was improved reliability, higher power was just a bonus. The Panther's reliability increased by the end of 1943 and it was now capable of driving 1000 km, but a number of issues remained. The overall image was not so good, even if one forgets such nuances as poor sideways vision.

It should not be a surprise that Pz.Kpfw.IV production only went up. 205 tanks were delivered in March of 1943, 272 in May, and over 300 a month by the end of the year. At least two attempts were undertaken to replace the tank. Guderian, at this point the Inspector General of the tank forces, initiated development of the Mehrzweckpanzer. This was an attempt to replace the B.W. chassis with a more modern tank with a more powerful engine and more importantly a modernized running gear. This project was stopped in October of 1943. The Pz.Kpfw.III/IV followed, a simpler and cheaper alternative, again with a new running gear. This tank no longer had 360 degree turret traverse (it was limited to a 270 degree arc). The project, born on January 4th, 1944, died in June of the same year. Krupp's project presented in November of 1944 suffered the same fate. They proposed installing a new turret with a 7.5 cm KwK 42 L/70 turret, except the exact same idea was rejected back in 1942 since the chassis was unsuitable for the task.

The last attempt to modernize the Pz.Kpfw.IV, November 15th, 1944. The suspension would not be able to hold up such a turret. The Germans were not only unable to carry out this modernization, but didn't even want to.

The situation around modernizing the Pz.Kpfw.IV was quite surprising. Krupp had the ability to modernize the running gear after their experience with the B.W.40, but waved it away since the tank was going to be replaced soon. When the clock struck, it turned out that there was no time left to act and production had to be ramped up as is. However, it was quite possible to modernize the tank. The bogey suspension and attachment of idlers and drive sprockets allowed for a similar change to the Medium Tank M4 HVSS. The Americans began thinking about modernizing their tank in the spring of 1942, but the Germans couldn't manage the same, even though the issue was also apparent in early 1942. It was not possible to load the tank any further after that. As a result, the Pz.Kpfw.IV turned into a whipping boy in the summer of 1944 when the Medium Tank M4(76)W and T-34-85 hit the battlefield in large numbers. An equivalent modernization was not possible. The Germans also could not make the decision to switch Nibelungenwerk (the only Pz.Kpfw.IV producer after June 1944) to building Panthers, even though plans were drawn up several times. The Austrians produced Pz.Kpfw.IV tanks like hotcakes, and that at least allowed them to plug the gaps in tank units that lose tanks faster than they could be built. 

The Panther and Pz.Kpfw.IV fought shoulder to shoulder until the end of the war. Even their losses were close: 3101 Pz.Kpfw.IV and 2803 Panthers were lost in 1944.

Even German plans for 1945 look naive and unrealistic. The Pz.Kpfw.IV would have remained in production as it was. Even the "budget" variant without a turret traverse motor was still quite a capable workhorse. Consider the fact that the Pz.Kpfw.IV remained in service after the war while the Panther was not so lucky. Trials of these tanks in the UK ended with some shocking revelations about reliability and other factors. The Germans made a core miscalculation. Experience in WW2 showed that the optimal tank weighed 30-35 tons, had a 500 hp engine and a top speed of about 50 kph. The Germans managed to either build a tank that could not exceed a mass of 25 tons or a 45 ton heavyweight that had nowhere to grow. The Germans were not alone in this. The Americans ended up building the Heavy Tank T26E3 that had no modernization reserve either, nor was its reliability much better than the Panther's. These tanks were supported by special repair brigades in WW2, but their weaknesses became apparent in Korea. The Pershing were retired at the same time as the Medium Tank M4 that they were supposed to replace. It was the M4A3E8 that ended up being the American workhorse in Korea. The parallels with the Pz.Kpfw.IV are very close, but in this case the Americans played their cards right and successfully modernized their workhorses.

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