The Tiger II Köningstiger was not the largest German tank created by the German tank industry. Much precious time and material was wasted on building prototypes of super-heavy tanks of gigantic proportion. Dr Ferdinand Porsche was the driving force behind the first of these, the 188-ton Maus (mouse), while the second type to be built, the 140-ton E-100, was supported by the Heereswaffenamt as a competitive design. Porsche got approval for his project from Hitler, at a time that none of his designs had been selected for production by the Heereswaffenamt. In this way Hilter might have compensated Porsche for the past failures, and it would keep him away from other projects.

The resulting Maus was a tank inventor's dream rather than a tank adopted to the tactical requirements of the battlefield. Initially the project was known under the code name Mammut (mammoth) and krupp was contracted to built it. Like Porsche's previous designs, the Maus had electrical transmission, and the internal layout, with a central engine of 1200hp, was similar to that of the Elefant. The armor was made up of flat rolled plates and the main plates were mortised and welded together. There were 48 partly interleaved wheels in four sets of four wheel bogies providing the suspension. The axles of each set of bogies were sprung and set on a longitudinal torsion bar. The vehicle had a relative low track height and the maximal road speed, via electrical generators under the turret floor, was 20 km/h. A snorkel tube provided air, allowing the Maus to cross rivers for few bridges could take the weight of the vehicle.

An early prototype of the Maus (205/1)	The second prototype of the Maus (205/2)

The turret had a rounded front made from a single bent plate of 93mm thick. The armament was either a 128mm or a 150mm gun, plus a 75mm gun mounted co-axially. The first turrets, with a weight of 50 tons, were not complete until the middle of 1944, leaving the two prototypes with a simulated turret to complete trials in the winter of 1943-1944, at Krupp's test area in Meppen. Two more hulls were under construction during the closing months of the war, but in April 1944, Hitler personally ordered that all work on giant tank projects was to cease in favour of devoting all resources to building proven tanks like the Panther and Tiger II. Most Maus prototypes were blown up in the last weeks of the war as the Russians closed in on Meppen, although guns, turrets and hulls were found by Allied Intelligence officers abandoned and partially destoyed. According to some sources however, the two experimental Maus tanks were sent into action in the final days of the war, one at the approaches to OKH staff headquarters at Zossen, the other near the proving grounds at Kummerdorf.

Design studies found at Krupp showed a version of the Maus carrying a 305mm breech-loading mortar, named 'Bear', and a giant 1500-ton vehicle with a 800mm gun as main armament and two 150mm guns in auxiliary turrets on the rear quarters. This vehicle put forward by two engineers named Grote and Hacker was planned to be powered by four U-boat diesel engines.

Test trials with the Maus (205/2)	Hull of the E 100 with armored track covers

The E 100 project was the Heereswaffenamt rival to the Maus, as there was considerable opposition to Porsche and his unconventional mechanical ideas. Under Heydekampf at the Panzer Commision ( Porsche was removed as head of this commision) a long-term plan was drawn up to produce a rationalised series of Entwicklung-typen (development-types) or E series. This range of tanks was to use standardised parts ans was to be built in classes of varying sizes to replace existing vehicles. The types had a designation with a number indicating their weight in tons: E 10, E 25, E 50 (Panther replacement), E 75 (Tiger replacement) and E 100. Of these only the E 100 project was actually started, as a attemp to rival Porsche's work. When Porsche started work on the Maus, an initial order was placed with Henschel, builders of the Tiger II, for a much enlarged, super-heavy version of the Tiger II. This project was known as the Tiger-Maus or VK 7001 PzKpfw VII Löwe (lion). The armament was to be the same 128mm gun as the Jagdtiger.

With the Entwicklung-typen programme, the VK 7001 order was replaced by the E 100, with the same gun and turret layout as the Maus, except that a 150mm or 170mm gun was envisaged as the main weapon. Road wheels, sprockets and idlers were to be similar to those used on the Tiger II. Armored covers were proposed for the tracks, which were one metre wide. Construction of the E 100 prototype proceeded slowly at Henschel's test plant after Hitler's order to cease work on super-heavy tanks, and at the end of the war only the bare hull and suspension were completed.