The basic design was ordered by the Waffenamt as a parallel development to the Porsche Maus in June 1943. It was the heaviest of the Entwicklung (E) series of vehicles, meant to standardize as many components as possible. There was going to be an E-5, E-10, E-25, E-50, E-75 and finally the E-100.
In November 1942, Krupp suggested a design weighing 155 tons, compared to the 188 tons of the Maus - but still using the Maus turret. In December 1942, Krupp suggested a design weighing 130 tons which used many of the same components as the Tiger tank with Maus turret — referred to as the "Tiger-Maus". Weight savings were to be from thinner armour, and narrowing and shortening the vehicle.