On June 23,1942, Dir. Dip. Ing. Grote (along with Dr.Hacker) from the Ministry of Armament, who was responsible for the production of U-Boots suggested the development of a tank with a weight of 1,000 tons. Hitler himself expressed interest in this project and allowed Krupp to go ahead with it. The project was designated as the Krupp P.1000 (Ratte - Rat). This behemoth "land cruiser" would be 35 meters long, 14 meters wide and 11 meters high. P.1000 would be equipped with 3.6 meters wide tracks per side made of three 1.2 meters tracks, similar to those used in excavators working in coalmines. It was planned to power P.1000 with two MAN V12Z32/44 24 cylinder Diesel marine engines with total power of 17,000hp (2 x 8,500hp) or with eight Daimler-Benz MB501 20 cylinder Diesel marine engines with total power of 16,000hp (8 x 2,000hp). According to the calculations, this would allow the P.1000 to travel at maximum speed of 40 km/h. P.1000 would be armed with a variety of weapons such as: two 280mm gun (naval gun used in Scharnhorst and Gneisenau warships), single 128mm gun, eight 20mm Flak 38 anti-aircraft guns and two 15mm Mauser MG 151/15 guns!!!
In December 1942, Krupp created the new design of a 1500 ton tank - P.1500. Its frontal armor would be 250mm thick and it would be armed with the 800mm super heavy barrel "Dora" type and possibly two 150mm artillery pieces. P.1500 would be powered by two to four submarine diesel engines for travel. In early 1943, Armaments Minister Albert Speer cancelled both projects. The P.1000 turret ended up at a coastal defense battery (Batterie Örlander) near Trondheim, Norway.
Prior to both the P.1000 and P.1500, in 1939, Krupp began working on other similar projects for a projected series of self-propelled coastal guns for the Kriegsmarine. The series was to include fourteen different platforms designated from R1 to R14. Armament was to range from 150mm to 380mm and they were to be mounted on fully traversable turntables on tracked carriages. One of the designs was the R2 coastal gun armed with a 280mm gun. The series never left drawing boards for obvious reasons.