100 Ton Mouse
After the fall of France in 1940, German designers got access to French developments, including full scale models of superheavy tanks, the FCM F1 and ARL Tracteur C. Compared to these tanks, the German VK 65.01 (Pz.Kpfw. VII) that started development in January of 1939 seemed obsolete. It's possible that this discovery led to the cancellation of the mild steel prototype.
Under the same index, a new, more powerful tank was designed. It seems that this is the tank mentioned in the intelligence report sent to the Red Army General Staff, dated March 11th, 1941. This report triggered work on the KV-3, KV-4, KV-5, A-44, and made serious ripples in other directions. The 90 ton mass fits in with later information about the vehicle known as VK 70.01. It really had a 105 mm gun and the mass was limited to 90 tons (the current limit of German railroad platforms).
Another confirmation that the VK 70.01 started its life before the fall of 1941 is the correspondence with Krupp regarding a new, even more powerful, 149 mm gun, which started no later than April. This same gun, with a length of 40 calibers, pops up again in November of 1941. The "heavy tank type VII" turned out to not be disinformation, fed to Soviet intelligence.
The vehicle that Soviet intelligence discovered wasn't anything like the commonly known VK 70.01. The hull and turret with sloped armour appeared only in late 1941, after the Germans ran into Soviet T-34s. Despite the index suggesting the vehicle was in the 70 ton class, the mass of the vehicle varied from 70 to 90 tons.
The same thing happened to the armament. The "canonical" version of the VK 70.01 is dated late January of 1942, and by early March, the project splintered. The VK 72.01 appeared, with either a 105 mm L/70 gun or 150 mm L/35 gun.
In September of 1939, the tank commission (Panzerkomission) was created, which acted independently of the 6th Waffenamt. It was headed by Ferdinand Porsche. A conglomerate headed by Porsche K.G. was in charge of conceptual design. The conglomerate also included Steyr-Daimler-Puch, Friedrich Krupp AG, Siemens-Schuckert AG, Skoda, and Nibelungenwerk, which were responsible for the engine, hull, electronics, suspension, and assembly, respectively. On March 22nd, 1942, this conglomerate was tasked with development of another 100 ton tank. This project was indexed VK 100.01.
The first mention of the VK 100.01 in Krupp's correspondence. The same letter mentions a 128 mm L/50 gun.
According to preliminary classification, the 100 ton class tank would have a 15 cm KwK L/40 gun with a capacity for at least 100 rounds. A part of the ammunition would be stored in the rear of the turret. Initially, the rounds would have been two piece, but a sketch of a one piece round was attached to a letter regarding the turret, dated April 18th, 1942. The overall length of the round was 1.6 meters, and it weighed 57.4 kg, 34 of which were for the shell. This was the lightened variant: initially, the 15 cm K18 round was used, which weighed 43 kg. The muzzle velocity of this shell was 875 m/s, and the rate of fire was an optimistic 4-5 RPM. As an alternative, the 12.8 cm KwK L/50 was proposed, with a 29.3 kg shell and 810 m/s of muzzle velocity. The design of the VK 100.01 was to be done by May 15th.
The first ever mention of the name "Maus" in documentation, dated May 18th, 1942. The gun was also changed on this day, shortened by 3 calibers.
Some changes were made to the tank design. First, the length of the gun was reduced to 37 calibers, dropping the muzzle velocity to 750 m/s. The length of the one-piece round decreased to 1530 mm, while the mass increased to 69 kg due to returning to the K18 shell. Second, the length of the 128 mm gun was deemed insufficient by Hitler, who personally supervised the project. He wanted an L/60 or L/70 gun. Finally, in a meeting on May 13th, Hitler proposed that even the 100 ton limit might not be enough, raising the bar to 120 tons. Hitler tried to accelerate the work on this superheavy tank with all his efforts. According to German intelligence, new Soviet heavy tanks would be ready by spring of 1943.
The change of name also happened around this time. The myth that the tank was initially called Mammut (Mammoth) is connected with this change. The date of this name's appearance was allegedly May 21st, 1942. Documents found in Bundesarchiv dispel this misinformation. By May 18th, the tank was already called Maus, and since summer of 1942, it was called "Mauschen" (little mouse) at least once.
As for the Mammut, this designation does appear elsewhere: in British intelligence reports, dated January 29th, 1945. This information was received from German POWs. Allegedly, two tanks were built under this name. Other tanks "discovered" in such a way include the exotic Adolf Hitler Panzer with two 88 mm guns (one in the turret and one in the hull). In other words, the name Mammut has no relevance to reality.
This is how the Typ 205 was initially: 120 tons, 16 cylinder air cooled diesel, 149 mm L/37 gun
On June 4th, 1942, Porsche K.G. presented Hitler with a draft numbered K.3381. This blueprint, labelled "heavy tank project" contained Porsche's vision for a competitor to the Pz.Kpfw. Lowe. The tank's mass was about 120 tons. The overall view of the tank was defined by a strict railroad transport limit and Porsche's refusal to use transport tracks. The turret was designed by Krupp, which also had a characteristic effect on the tank's looks.
The superheavy tank from Porsche K.G. was similar to the Pz.Kpfw. Lowe. Unlike later redesigns, this was a classically laid out vehicle with a turret in the center of the hull. The length of the hull was slightly longer than the Pz.Kpfw. Lowe in May of 1942 (8331 mm vs 7740 mm), but the overall length was less (10,620 mm vs 10,760 mm). The tank's height was 3.3 meters and width was 3.45 meters.
Seeing this tank, Hitler agreed that it could serve as a "mobile fortress". This was not only because of the tank's size. Porsche K.G. developed a new 16 cylinder V-shaped engine for the new tank. With this engine, the vehicle's maximum speed was rated at 20 kph. The engine was connected to a generator, which transferred the energy to electric motors in the rear of the hull.
Due to the tank's weight, it received a massive suspension. It used two-wheel bogies with a torsion bar suspension from the Typ 101 (VK 45.01), which were attached to the spaced armour and hull sides. Each side would have 6 bogies. It must be said that servicing this arrangement would have been difficult. This dual layer design was made necessary by the fact that the tracks were about a meter wide. As a result, the compartment where the driver and radio operator were placed was very narrow. Porsche's engineers spread the tank's hatches very widely, so climbing into the tank or getting out was not a simple task.
Reconstruction of the overall view of the VK 100.01, June 4th, 1942
Of the tank's 120 tons, 23 were used up in the turret. It had many elements of the Pz.Kpfw. Lowe, down to the gun mantlet that almost perfectly repeated the contours of its lighter competitor. The turret had a 149 mm L/37 gun with a massive muzzle brake. 30 one-piece rounds were stored in the turret. Another 36 were going to be stored in the hull. The question of there they would have gone is an interesting one indeed.
105 mm L/67 gun, proposed by Krupp as a alternative weapon for the Pz.Kpfw. Maus in June of 1942.
Upon seeing the project, Hitler agreed with the general idea, but proposed that Porsche think about thicker armour and protection from enemy infantry. The project had no machinegun. Porsche's engineers thought for a while and came up with draft K.3382 on June 17th, 1942. The name Maus can be seen on this blueprint. On July 23rd, Hitler rejected the idea of infantry protection, suggesting that the tank should be accompanied by separate tanks with short 75 mm guns for support.
This is not surprising, as the new tank resembled a pagoda. Krupp's engineers placed another smaller turret on top of the main one, equipping it with a 75 mm L/24 gun from the PzIV. As a result, the tank grew to almost 4 meters in height. A 105 mm L/70 gun was offered as alternative armament. Hitler preferred it, since it had a higher rate of fire.
Blueprint K.3382, made on June 17th, 1942, in response to Hitler's suggestion to increase the armour thickness and install a gun to protect against enemy infantry.
Hitler approved Porsche's concept, but even the thicker armour did not satisfy him. He wanted more armour, which led to more mass, which led to a complete redesign of the tank. Pz.Kpfw. Lowe couldn't compete and was cancelled on July 20th, 1942.
This is the Song That Never Ends
On June 25th, 1942, Krupp supplied the first draft of a completely reworked turret. Almost a month later, on July 17th, the 6th Waffenamt and Krupp signed contract #SS 006-4467/42 for the development of a turret for the Pz.Kpfw. Maus. The 128 and 105 mm guns were left out, and the designers settled on a 149 mm gun. The length of the barrel was reduced to 31 calibers, which was about the same as the sFH 18 gun family. The gun, indexed 15 cm KwK L/31, had one piece ammunition.
Nevertheless, the 15 cm L/31 gun remained in correspondence until March of 1943. A coaxial 75 mm L/24 gun was meant to fight infantry and lightly armoured targets. The armour thickness of the turret was 250 mm in the front, 200 in the sides and rear, and 80 mm in the roof. Overall, the turret weighed 57 tons, including the weight of 25 149 mm shells and 50 75 mm shells.
Even though the turret was designed for the 15 cm KwK L/31, the Porsche K.G. project supported the guns proposed in June requirements: the 15 cm KwK L/37 or 12.8 cm KwK. Both guns had a portion of their ammunition in the turret and a portion in the sponsons. None of the guns had the 100 rounds that Hitler demanded. By October of 1942, the mass of the turret and armament was estimated at 47 tons.
The redesigned Pz.Kpfw. Maus was presented by Porsche on October 5th, 1942. By October 28th, blueprint K.3384 was ready. The mass of the tank increased only a little bit compared to the late June version, a mere 10 tons. The tank, however, changed beyond all recognition. The new turret had a larger turret ring, so the sloped sides had to go. The hull resembled a box with a sloped rear and front. There was a new feature, a machinegun mount in the hull. Due to the longer and heavier hull, there were now 8 road wheels per side. For ease of service, instead of one wide track, there were now two narrower ones, like on the VK 40.01(P).
Blueprint K.3384, October 5th, 1942. The Pz.Kpfw. Maus changed beyond recognition.
The project was proposed in two variants. The first, indexed Typ 205A, had a 12 cylinder V-type water cooled 42.4 L Daimler-Benz diesel engine, which produced 1000 hp at 2400 RPM. The second, Typ 205B, had a Typ 141 engine developed by Porsche K.G. This was an 18 cylinder air cooled 41.5 L diesel engine that produced 780 hp at 2400 RPM.
A decision was made to keep it safe and develop both projects in case one engine doesn't work out. In November, the main candidate for installation became the Daimler-Benz 603 aircraft engine. Its power output could be increased to 1500 hp with a compressor.
A wooden model of a turret. Note the somewhat different observation device design.
This increase in power was mandated by the fact that the tank's armour kept growing and it now weighed almost 170 tons. Understanding that this kind of weight will cause trouble, Porsche allowed the turret armour to be decreased by 10%. Thanks to this, the mass of the turret dropped to 43 tons. In early November of 1942, the tank was reworked again. By November 14th, blueprint K.3385 was ready, where the turret moved to the rear of the hull. Similar metamorphoses happened to the Porsche Typ 180 heavy tank (VK 45.01(P)).
This is what the tank looked like in mid-November, 1942.
From December 1st to 3rd, 1942, the redesigned tank was examined by a commission headed by Hitler. The vehicle was finally approved, with a ton of conditions regarding the armament and other features. The 128 mm gun resurfaced. The approval of the Pz.Kpfw. Maus meant the end of the competing Tiger-Maus project developed by Krupp. Work on that vehicle was stopped on December 15th. As for the Maus, its next reincarnation came on January 1st, 1943 (blueprint K.3387). The turret was simplified, the commander's cupola was changed and shifted back. The loader's hatch was removed. The coaxial 75 mm gun was lengthened (later this gun was indexed 7.5 cm KwK 44 L/36). The hull also changed, but negligibly.
Reconstruction of the Pz.Kpfw. Maus as of January 1st, 1943 (blueprint K.3387). These were the last radical changes, and from here on out the tank changed a lot less.
The project changed once again only a week later. By spring of 1943, numerous changes were made. Nevertheless, a tank was built according to K.3387, and it even moved. Of course, this is a 1:5 scale remote controlled model, which was demonstrated to Hitler on May 14th. At the same time, a 1:1 model was shown. This was another tank a much heavier one, very similar to the one that was eventually built in metal.
Demonstration of the Maus tank model to Hitler, "Wolf's Lair" headquarters, May 14th, 1943