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Grosstraktor (“Large Tractor”)

With Germany’s defeat in the Great War, the country faced various military constraints pursuant to the terms of the Treaty of Versailles, which prohibited Germany from possessing tanks, among other military restrictions. With activities being closely monitored by the Allied Control Commission, development of Tanks occurred in secret. A sample tank was received from the Swedish machinery manufacturer AB Landsverk; called the Gutehoffnungshütte (“Großtraktor”). AB Landsverk would go on to be the main manufacturer of tanks for Sweden.

In 1926 Rheinmetall-Borsig, Daimler-Benz and Krupp were commissioned to develop a 20 ton tank. The vehicle was dubbed Großtraktor (“Large Tractor”) and was developed at the same time as another vehicle, the Leichttraktor (“Light Tractor”) (“Leichttraktor”). With the Nazi rise to power, the experimentation in Russia was halted and the prototypes brought back to Germany were they initially served a training role. The prototypes were decommissioned in 1937 due to inadequacies evident in their use as training tools; at least one ended up as a memorial to early armored regiments.

The Großtraktor was designed as a heavy breakthrough vehicle. The prototype vehicles had differences; however what follows was true of at least one or more of the models. The main armament was the same short 7.5 cm gun initially used on the Panzer IV; with secondary armaments including multiple machine guns. The approximate weight being 16 ton. The engine was a six-cylinder engine, in the 250-260 hp range. The following may have applied only to the Rheinmetall-Borsig and Krupp designs: a machine gun was placed at the rear of the tank, behind the turret; and the tank commander sat not in the turret, but in the hull to the right of the driver.

In 1925, Rheinmetall-Borsig, Daimler Benz and Krupp were ordered to design medium (heavy) tanks – codenamed Armeewagen 20 (Army Car 20). The following specifications were to be fulfilled: length of 6m, width of 2.4m, 75mm gun mounted in a rotating turret and weigth of 15 tons. The tanks mounted a stubby 75mm cannon in it’s main turret located at the front, and carried a smaller turret behind the engine that mounted a rearward-facing machine-gun. Each company was to produce two mild steel (6-14mm) prototypes disguised as commercial vehicles. Krupp designed their own turret, while Rheinmetall designed a turret to be mounted on their own design and that of Daimler-Benz. Work started in 1925 and tests were planned for 1929/30.

Daimler Benz’s Grosstraktor I was designed by Dr.Porsche and was armed with single 75mm KwK L/24 gun and three to four 7.92mm schwere MGs. It had amphibious capabilities and was powered by Daimler M182206, 6-cylinder gasoline engine with total power of 255(260)hp. It had a leaf springs sophisticated suspension and hull design. Only two mild steel prototypes were built in 1929 (nr.41) and 1930 (nr.42) and were secretly tested. It appears that one of the prototypes was rearmed with a longer version of 75mm gun.

Rheinmetall-Borsig’s Grosstraktor II was armed with single 75mm KwK L/24 gun and three to four 7.92mm schwere MGs. Its overall design was simpler from that of Grosstraktor I, it included side access doors and also had amphibious capabilities. Only two prototypes were produced, first in 1928 (nr.45) and the second one in 1929 (nr.46), while both were then modified in 1930, 1932 and 1933. Rheinmetall’s design was powered by 6-cylinder BMW Va engine with total power of 250hp.

Krupp’s Grosstraktor III was also similar to other designs but differed with many detail differences. Also only two prototypes were produced, first in 1928 (nr.43) and the second one in 1929 (nr.44), while both were then modified in 1931. Both vehicles had coil springs suspension and their weight (16-16.4tons) and speed (40-44km/h) depended on the prototype. The two prototypes made by Krupp were made from simple low-carbon steel rather than armor plate.

In general, all were similar in design to British Medium Tank Mark III (which was also produced in limited number and used for testing) and Medium Tank Mark C (some 36 were produced before the Great War ended along with with 14 completed afterwards).

As the 1920s were coming to an end; Germans began performing experiments in secret in Russia. The Treaty of Rapallo, signed in 1922 in secret between Russia and Germany, provided the ability for experimentation near Kazan in Russia. The testing facility near Kazan was called Panzertruppenschule Kama (Armoured Troops School Kama) and was used from 1926 to 1933. The location was a joint testing ground and tank training ground for both the Russians and Germans. The term Kama comes from the two words Kazan and Malbrandt; Kazan being the nearby town and Oberstleutenant Malbrandt being the individual given the task of selecting the location used for testing.

In 1931, 289 were ordered, but in 1932, this project was cancelled in favor of other developments and both Krupp and Rheinmetall produced only 3 prototypes.

In 1933, after completed tests and end of co-operation with the Soviet Union, four functional vehicles returned to Germany. Krupp and Rheinmetall-Borsig prototypes were used for training purposes in continuation with the work started at Kama. Eventually, they were handed over to the 1st Panzer Division and took part in maneuvers in August of 1935. Both Daimler-Benz Grosstraktors ended up as monuments at 1st Panzer Regiment headquarters at Erfurt and 5th Panzer Regiment headquarters at Wundsdorf. After 1935, remaining four prototypes were used for training purposes at Panzer Gunnery School at Putlos. In 1937, one of Krupp and Rheinmetall Grosstraktors ended up as a monument at 5th Panzer Regiment headquarters at Wunsdorf. The remaining two were either scrapped or used for target practice.Grosstraktors were extensively tested and lessons learned from them provided the German designers with valuable experience, which was then used in the direct development of Neubaufahrzeug and eventually of other designs.