The 10.5 cm K18 auf Panzerselbstfahrlafette IVa, popularly known as “Dicker Max”, was an experimental German heavy tank destroyer (Panzerjäger) developed by Krupp on a modified Panzer IV Ausf. E chassis to neutralize enemy fortifications and heavily armored vehicles. Ordered in late 1939 and presented to Hitler in March 1941, the vehicle featured an open-topped armored superstructure (10 mm to 50 mm thick) housing a powerful 10.5 cm K 18 L/52 gun fitted with a muzzle brake, capable of penetrating up to 111 mm of sloped armor at a range of 2,000 meters. Powered by a Maybach HL 120 TRM engine and equipped with a stowable MG 34 for close defense, only two prototypes were completed before serial production plans were abandoned in favor of other designs. Deployed for combat evaluation with Panzerjäger-Abteilung 521 during Operation Barbarossa, the vehicles proved highly effective against Soviet heavy tanks such as the KV series; however, one prototype was destroyed by an internal ammunition fire, while the second fought through Operation Fall Blau near Stalingrad before being abandoned, leaving no surviving examples.
