While still fighting in Poland in September 1939, the German High Command looked ahead to the coming battle with France and ordered a vehicle for use against the fortifications of the Maginot Line. In response, Krupp set about designing a self-propelled 10.5cm gun based on a Panzer IV tank chassis. The new vehicle’s rotund profile quickly gained it the nickname ‘Dicker Max’ (‘Fat Max’).The two prototypes were assigned to the 521st Heavy Tank-hunter Battalion for a planned attack on Gibraltar. When this was cancelled, they were assigned to the 3rd Panzer Division for Operation Barbarossa, the invasion of the Soviet Union. One Dicker Max was lost in an ammunition explosion and the other returned to the factory in October 1941 after three months in combat.