On 23 June 1942 the German Ministry of Armaments proposed a 1,000 tonne tank—the Landkreuzer P. 1000 Ratte. Adolf Hitler expressed interest in the project and the go-ahead was granted. In December of that same year, Krupp designed an even larger 1,500 tonne vehicle—the P. 1500 Monster.
In 1943, Albert Speer, the Minister for Armaments, canceled both projects.
The Landkreuzer P. 1500 Monster was to be 42 m (138 ft) long, weighing 1500 tonnes, with a 250 mm hull front armor, fourMAN U-boat (submarine) marine diesel engines, and an operating crew of over 100 men.
The main armament was to be an 800 mm Dora/Schwerer Gustav K (E) gun, and with a secondary armament of two 150 mmsFH 18/1 L/30 howitzers and multiple 15 mm MG 151/15 autocannons. The main armament could have been mounted without a rotating turret, making the vehicle a self-propelled gun rather than a tank. Such a configuration would have allowed the P. 1500 to operate in a similar manner to the original 800mm railroad gun and Karl 600mm self-propelled mortars, launching shells without engaging the enemy with direct fire.