Friday 30 December 2022

The Elusive Maus

Great Britain and the USSR actively exchanged information on the enemy during WWII. The USSR even shared its trophies, for instance, Panther and Pz.Kpfw.III Ausf.L tanks captured in the USSR were sent to the UK. However, these relations soured after the end of the war and the exchange of information ceased. As both experimental Maus prototypes ended up in the hands of the Red Army, the British had to collect scraps of information on this tank across their occupation zone. How well did British investigators do and how truthful was the information they collected?

The Final Squeak

The Maus is first mentioned in the DRAC (Director, Royal Armoured Corps) Technical Intelligence Summary for May 1945. The description is rather brief:
“Developments in German tank design appear to have been mainly limited to the super-heavy class. Three equipments falling under this heading have so far been examined as follows:
Maus (Mouse). This is a tank with an estimated weight of 200 tons mounting a 12.8 cm Kw.K.82 (L/55) and a co-axial 7.5 cm Kw.K.44 (L/36.5) in a turret with 360° traverse.”
The summary also described the E-100 tank and Grille SPG, but there was likewise little information on those vehicles.

 Officers of the 1st Polish Armoured Division and three sets of Maus armour parts, Krupp proving grounds in Meppen.

It did not take long before additional information became available. Three Maus hulls and turrets were found at the Krupp proving grounds in Meppen. They were empty, but a mounting with a 128 mm and a 75 mm gun was presumably associated with them. Documents found at the proving grounds indicated that the gun used to be called 12.8 cm KwK 44 (Maus) and was later renamed 12.8 cm KwK 82. The documents also indicated that this tank was not produced in large numbers and no more than six sets of hulls and turrets had been built. The three sets at the proving grounds were taken there for penetration trials. The Maus’ guns were also experimental and arrived in Meppen in November of 1943 for trials. A label on a crate with ammunition was dated January 3rd, 1944.

The report indicated that the design of the hulls and turrets differed from the latest German developments. The plates were interlocking and the number of angled surfaces was minimal. The tank effectively had spaced armour along the sides, as the skirt armour descended past the fighting compartment floor.

The engine was not in the rear, as usual, but in the middle, between the fighting and driver’s compartments. The transmission was in the rear. There were no transmission components in the hull, but the report author assumed that the transmission would be electric, like on the Elefant tank destroyer.

British measurements of the Maus’ armour. Some measurements are approximate.

The British didn’t have time to weigh and measure the parts before the report was written. The estimated mass of the turret was 34 tons, and the whole tank weighed about 200 tons. The dimensions of the turret, hull, and tracks were also approximate.

The British were in a rush to obtain information about the tank and didn’t check their sources thoroughly, questioning anyone who they could get their hands on. For instance, the main source of initial reports was an engineer who worked at the proving grounds. There was only one issue: he had no experience with the Maus, and in fact no experience with tanks at all. His speciality was concrete and his job was to build an underwater test drive course for the tank. Everything he knew about the Maus was based on rumours, and so one should not be surprised that his information was not entirely correct.

According to the source, work on the project began in the spring or summer of 1942 with the support of the Minister of Armaments and War Production Speer. The tank was allegedly called Mammut (Mammoth). In 1943, the engineer in question was tasked with building an underwater driving course that could hold a 200 ton tank. This was a very interesting task, as the mass of the Mäuschen tank (Little Mouse) was only 100 tons by then. From conversations with military representatives and other engineers, he learned that the new tank would have a diesel MB 517 or gasoline DB 603 engine, an electric transmission, parallel torsion bars like the Elefant, and protection from poison gas. The crew numbered 6-7 men.

According to the engineer, one Maus was built and tested in Linz, Austria, where it remained until the end of the war. As for the project as a whole, Hitler cancelled it in early 1944 due to excessive cost and a shortage of copper.

A more reliable source was also questioned, but even he could not give precise information about the project. According to Kurt Arnold, the head of the Henschel proving grounds, the tank was initially supposed to weigh 150 tons, but it grew to 200 tons during development. The Maus was powered by two 850-1000 hp engines which never reached the required level of reliability. The tank could only be moved across large distances by rail. The armour was 190-210 mm thick and additional 90 mm thick plates protected the suspension. The conclusion of his story coincided with the one told by the concrete engineer: the project was closed in April of 1944 due to technical complexity and unfavourable situation on the front lines.

With no other sources of information, the British continued to inspect the components and assemblies available. Specialists noted that the wide tracks severely limited the amount of space inside the tank. Even though the space between the upper sides was 3645 mm wide, the distance between the lower sides was just 1155 mm. This limited the height of the fighting compartment, as the turret basket floor could not be lower than the panniers.

The hull consisted of four sections separated from each other with 20 mm thick bulkheads. The driver’s compartment was located in the front. As mentioned above, the British could only guess as to the number of crewmen located here. The 100 mm thick compartment roof had a 900 by 380 mm oval opening cut in it for a hatch. There was a small opening in front of it, presumably for a periscope, and another very small one, presumably for a ventilation fan. A round 520 mm wide opening was cut into the floor for an evacuation hatch.

Maus hull layout. Note the number of question marks indicating how much was still unknown about the tank.

The engine compartment was situated behind the driver’s compartment. The roof over it was missing, but the British estimated that the armour would be 60 mm thick here. The engine was presumably mounted in the middle of the compartment with fuel tanks along the sides. The engine compartment was separated into six sections, but the British could not guess what they were used for.

The fighting compartment was next. Its roof consisted of four 60 mm thick plates welded together. As the fighting compartment was completely empty, it was hard to say anything definite about it. Finally, the rearmost compartment was reserved for the transmission. It was split into three sections with 20 mm thick armoured bulkheads. The report author assumed that the electric transmission that the engineer described would be installed here.

Having measured the hull, the British estimated that it weighed about 68 tons.

The turret was described as “a massive structure, incredibly tall for its width and length”. Its mass without any components was estimated at 34 tons. Its curved front armour was compared with that of the King Tiger, mistakenly attributing its design to Dr. Porsche. An opening for the gun was cut in the front of the turret, shifted to the right from the central axis by about 200 mm. This allowed the specialists to estimate the size of the gun mantlet. The floor of the turret was welded together from two 93 mm thick plates with localized weak spots. A 35 cm wide round opening was cut in the top of the turret and a 25 cm round opening was cut in the rear. As neither was large enough for a hatch, the report author assumed that the hulls and turrets were sent to Meppen before they were fully cut.

A drawing of all known parts of the Maus fitted together. The British had no information about the design of the running gear and gun mantlet.

The tank’s armour was only rolled. It was difficult to measure the thickness of such thick plates, but the measurements made by British specialists did not noticeably differ from those later made by the Soviets.

The guns meant for the Maus were tested separately. There was no muzzle brake installed on the 12.8 cm KwK 82 L/55, but the author did not eliminate the possibility of other barrels with threading for a muzzle brake being found later. The horizontal sliding breech opened to the right. A standard electric firing mechanism was used. The main gun was located in the left part of the dual gun mount. It had to be shifted very far back in order to maintain balance. The recoil brake and recuperator were located above the barrel. The overall length was 7020 mm, the rifled part of the barrel was 5533 mm long. Calculations showed that a 28.3 kg 12.8 cm PzGr 43 shell would have a muzzle velocity of 750 m/s with a medium propellant load or 920 m/s with a full load.

The same Maus, view from above.

The coaxial 7.5 cm KwK 44 L/36.5 was completely new, although the author did not exclude the possibility of using ammunition from the 7.5 cm KwK L/24. The gun also had a horizontal sliding breech that opened to the right and an electric firing mechanism. This gun was placed to the right of the main gun and could block its breech if recoiled fully. The recoil brake was located under the barrel, the recuperator above it. Both guns shared a cradle, produced as one cast part. It was attached to the front wall of the turret via a protrusion in the front part. The British estimated that both guns and the cradle weighed at least 5 tons.

Using known ratios of the weight of armour to other components, the British estimated that a fully stowed Maus would weigh about 214 tons.

After study of the hulls, turrets, and cannons was completed, there was nothing else to investigate. The Maus remained a mystery, but there were no additional materials to explore. Another report was published on June 27th, 1945, but it largely contained the same information gathered in May, including quoting the concrete engineer’s testimony word for word. An additional note was made, indicating that the tank likely initially had the DB 603 engine and it was later replaced with the MB 517. There was also some new information about the transmission. New information about the tank’s weight became available, it turned out that it weighed a mere 176.5 tons instead of 214.

Hot on the trail

The British obtained some information by the fall that cleared up the situation. An appendix to Technical Information Summary #186 published on October 11th, 1945, contained a summary of the minutes of a meeting between Porsche, Hitler, and Speer held on June 9th, 1942. After discussing the installation of an 88 mm L/71 gun into the Tiger (P), the conversation moved on to a tank with a 128 or 150 mm gun in a rotating turret with a 75 mm coaxial gun, or an SPG with a 180 mm gun, 200 mm of armour in the front, and 180 mm in the sides. The armour of the turret or casemate would be even more impressive: 220 mm in the front and 200 in the sides. Porsche recommended using a diesel engine, but Speer was against it, claiming that there was no time to develop one.

 Diagram of the Daimler-Benz MB 509.

A summary of the history of the Maus’ development followed. Porsche and his electric transmission specialist Otto Zadnik decided to reuse the same idea tried on the Ferdinand, but with serious changes. Contrary to Speer’s desigres, Porsche decided to use a diesel engine. Daimler-Benz could not hold up their end of the bargain. In November Porsche learned that it would not be possible to get an engine in time. He had to use an MB 509 gasoline engine after all (called DB 509 in the document). The design of the transmission had to change slightly in order to accommodate it.

In late 1942 the German Ordnance Directorate attached a curator to the project, Colonel Henel. His job consisted of traveling to various subcontractors to threaten them with fines and punishments if the orders were not fulfilled in time. For instance, Henel turned up in Stuttgart on December 13th, 1942, and demanded that the hull of the Maus be ready for trials by May 5th, 1943. His demands had no effect and his visits were considered quite amusing.

Overall layout of the Maus tank.

In early January of 1943 Porsche was summoned to Berlin to show Hitler a model of the tank. The Fuhrer liked it, but did not make any specific requests or comments.

By January 12th the work was separated in the following way. Krupp was responsible for the hulls and turrets, Daimler-Benz was building the engine, Siemens-Schuckert built the electric components, and Skoda handled the suspension and running gear. Final assembly would take place at the Alkett factory.

Work began, but heated discussion continued. Heinrich Kniepkamp was categorically against this design, insisting that it would be far too unreliable. Colonel Henel, on the other hand, tried to add more features to the design, claiming that it was mandatory for the tank to have a flamethrower with a 1000 L fuel reservoir. Weight calculations dampened the Colonel’s enthusiasm. The flamethrower would have made the already overweight tank much heavier. In addition to the gun mount, the suspension would have to be redesigned. The latest German designs were already using torsion bars, but Porsche didn’t want to risk it. He ordered a simple volute spring suspension from Skoda.

A suspension bogey and track segment.

A cooling system was tested at the Stuttgart Technical Institute under the supervision of Professor Kamm. Its effectiveness was deemed satisfactory.

Work was well underway. Speer arrived at Stuttgart on April 6th, 1943, and inspected the model of the tank for half an hour. An order arrived on April 10th to move the model to Berlin so it could be shown to Hitler, but cancelled on April 16th. Hitler finally had a chance to personally see the model on May 14th. Upon seeing the tank, he remarked that it looked like a child’s toy and ordered the installation of a 150 mm gun. The author of the report expressed doubt that Hitler would have given this order purely from an aesthetic point of view, a 150 mm gun was indeed developed for the Maus.

A Maus track link.

The MB 509 engine arrived at Stuttgart on July 16th just as the cooling system was ready. By all accounts, the conversion of the engine from an aircraft model to a tank one was not difficult, but a decision was nevertheless made to assemble the second Maus prototype with the MB 517 marine diesel.

Everything seemed to be going well. Alkett began working on assembly of the first prototype on August 1st, 1943, when the first bad news arrived. Krupp would be unable to meet its deadlines due to heavy bombing. The first hull was finished by mid-September, but the fall of 1943 proved fatal to the Maus. At a meeting with Porsche in Berlin on October 27th Speer announced that mass production would not take place. Nevertheless, work on the “Maus I” with the MB 509 gasoline engine and “Maus II” with the MB 517 diesel continued.

An American soldier at the Krupp factory measuring the dimensions of a Maus hull. Bombing of the subcontractor factories killed the project.

A Maus tank (the specific vehicle is not identified in the document, but this was the Maus I) entered trials on December 23rd, 1943. As the turret did not yet arrive, a 55 ton dummy weight was installed instead. Suspension springs broke during trials, the exhaust pipes rusted quickly due to low quality of metal, there were issues with the electric transmission. Nevertheless, the trials were considered a success and the tank was sent to Böblingen for further trials.

The tank arrived at the proving grounds on January 10th, 1944. It showed itself well when personally driven by Otto Zadnik. Witnesses claimed that it was capable of any maneuver that the Panther tank could pull off. Of course, this did not include the top speed. The colossus could only reach a speed of 22 kph on good terrain. Hitler ordered that a real turret should be installed on the Maus by June.

A diagram for the Maus turret as built (left) and with a prospective rangefinder (right).

The turret arrived on May 3rd. The gun, traverse mechanism, and other components arrived a few days later, and assembly was completed by June 9th. Subsequent trials showed that mobility improved, as the turret was a little lighter than the 55 ton dummy. The tank remained at Böblingen until early October, when orders were given to move it to Kummersdorf.

Meanwhile, work on the Maus II continued. The tank arrived at Böblingen on March 20th, 1944. The engine was only ready in September. Test bench trials showed impressive results. The engine arrived in Böblingen in early October. It was immediately installed in the tank, which was shipped to Kummersdorf without additional trials. This was a mistake. The shaft broke as soon as the tank was started up in Kummersdorf, likely due to poor assembly. The engine mounting loosened in transit, which caused it to shift and break.

A Maus hull at the Krupp factory.

The new MB 517 arrived at Kummersdorf only in March of 1945. The team of technicians sent by Porsche returned to Stuttgart on April 3rd. They reported that the engine was successfully started, but the tank was not moved. As far as the British knew, both tanks were still at Kummersdorf when Germany surrendered.

Casual conversation

Since Kummersdorf fell in the Soviet occupation zone, the British had no chance of obtaining a Maus tank for trials. Nevertheless, factories and specialists who took part in the creation of the tank were still accessible.

 A Maus tank turret at the Krupp factory.

Interrogation of Krupp personnel in Essen and inspection of partially assembled hulls gave a lot of information about the project. The Germans stated that the hull and turret were developed by Krupp in June of 1942 and production began in May of 1943. The BIOS (British Intelligence Objectives Sub-committee) report on assembly of hulls and turrets at German factories repeated incorrect data on the Maus. Even though the thickness of the armour was underestimated, the mass of the tank was given as “approximately 200 tons”. Based on the information gathered at the factory, Krupp built three sets of armour. One was sent to be used in penetration trials, the rest remained at the factory.

Work with the Americans bore more fruit. A CIOS (Combined Intelligence Objectives Sub-committee) report on the work performed by Dr. Porsche during the war contained a large amount of information about the Maus tank, including blueprints.

Cutaway diagram. Despite the tank’s colossal size, there was very little room inside.

The interrogation of Porsche gave some very interesting results. According to him, the tank was put into production. The report noted that Speer, Heydekampf, and other high ranking staff did not agree with this assessment. Porsche described his brainchild as a “mobile bunker”, but the report author indicated that several Tiger or Panther tanks would cost about the same as one Maus, but be much more effective even in a purely defensive role.

The designation “mobile bunker” described the tank well. With up to 350 mm of effective front armour, its top speed was just 20 kph. This made the design of the suspension much simpler. To avoid losing such an expensive tank to mines it had to be protected from the bottom as well. A special railroad platform would have to be designed to transport it.

Suspension layout of the Maus.

As there were few bridges that could carry this monster, the tank had to be able to cross rivers up to 7-9 meters deep underwater. The mechanism developed by the Germans was described as “original, but not very practical”. Since the tank could not develop full engine power using just the air supplied through a hose, the Germans found another way. One Maus remained on land and supplied electric current to the second Maus, which crossed the obstacle, after which their roles reversed. It took 45 minutes to prepare for this procedure, during which time the crews had to exit their vehicles. Both river banks had to be thoroughly prepared. Since the Maus was supposed to fight with the support of lighter tanks, this was considered acceptable. Inspection of the hatch designs showed that only the driver and radio operator had any chance of escaping the vehicle if it broke down while underwater.

Porsche also gave the exact weight of the tank (184.4 tons) and its components. 41.8% of the overall mass was taken up by armour. To compare, the Churchill III used 40.7% of its mass for armour, the Cromwell only 34.7%. 16% of the mass went to the suspension and running gear, compared to 21.0% and 25.7% respectively. The weight of the massive transmission was proportionally comparable to that of the British tanks: 7.9%, 7.0%, and 7.4% respectively.

A partially mechanized ready rack was installed in the turret bustle.

The armament took up a larger percentage of the mass: 27.5% versus 14.3% and 19.3% on the British tanks. The turret, armament, and ammunition weighed about 50 tons. This made the traverse mechanism’s job difficult, especially as the turret would be badly out of balance. It was clear that the designers put armour and armament first, everything else was secondary.

Since Porsche did not directly take part in the development of the armament, his description of it had several mistakes. For instance, Porsche stated that the coaxial 75 mm gun was identical to the one used on the Pz.Kpfw.IV. Porsche also mentioned that the main gun could be replaced with a 150 mm L/38 gun, but he did not have precise information.

The recoil length of the 128 mm L/55 gun was 960 mm. It was balanced with a counterweight. According to Porsche, the placement of the machine guns was poor due to the cramped turret, but there was not enough space to develop a better mounting.

Ammunition racks in the hull. The question of how the loader would bring the enormous rounds up into the turret to refill the ready rack is difficult to answer.

Since lifting the 56 kg 128 mm or 70 kg 150 mm rounds by hand would be impossible, a loading mechanism was developed, but two loaders were needed to operate it. If the 150 mm gun was installed, it would have to use two part ammunition. The tank could fit 60 or 68 (depending on the source) rounds of 128 mm ammunition and 200 rounds of 75 mm ammunition. The expected amount of 150 mm rounds carried is unknown. Porsche knew nothing about the gun sight, but said that a rangefinder was planned.

The Anglo-American commission also obtained the results of trials. The tank could cross a 0.72 m tall wall and a 4.5 meter wide trench. Given an average speed of 16 kph, its cruising range was 190 km with the external fuel tank. The cooling system was a big problem. Even though the fans took away a whopping 148 hp from the engine, the motors overheated after 15 minutes of running at maximum power.

Calculated weight bearing on each road wheel.

The Maus was truly one of a kind. In making his “mobile bunker”, Ferdinand Porsche applied many unique solutions, both questionable and ingenious. Nevertheless, the victors of WWII had little interest in his work. Both the British and Americans already had experience in building slow and heavily armoured behemoths, and both ended poorly. Even though the Maus was new to British and American intelligence, the vehicle was based on technical solutions developed in 1942-1943 and was too old to truly be impressive.

  • Report of Investigation into the War Time Activities of Dr. Ing. h.c. F. Porsche, K.G.
  • BIOS Final Report №614, Item №18, Welding Design & Fabrication of German Tank Hulls & Turrets
  • CIOS Evaluation Report #244 — Henschel Tank Proving Grounds
  • Canadian Military Headquarters archive, London (1939-1947) RG 24 C 2
  • Y. Pasholok, I. Zheltov, Panzerkampfwagen Maus — М.: «Tactical Press», 2012

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