As of September 1st of 1939, Germany army didn’t posses any tank destroyers in its arsenal. Army relied on towed artillery pieces such as light 37mm Pak 36 guns and heavy anti-aircraft 88mm Flak 18 guns. The need for mobile artillery of all types was a requirement of the mobile warfare developed by the German high command.
In September of 1939, German High Command ordered Krupp to design a heavy panzerjager (or mobile platform) armed with 105 or 128mm gun that would be able to destroy enemy tanks and heavily fortified positions (such as pillboxes). The requirements for the vehicle almost foreshadow the upcoming invasion of France in the Summer of 1940, where such vehicle would engage both the French defenses of the Maginot Line as well heavy French tanks such as Char B-1.
In early/mid 1941, Krupp-Gruson produced two prototypes of the new vehicle and on March 31st of 1941, first one was presented to Adolf Hitler. The Fuhrer ordered further development of heavy panzerjagers armed with either 105mm or 128mm guns. He also ordered that the production of Selbstfahrlafette 10.5cm must start in the Spring of 1942, but it was later on cancelled in favour of other vehicles.
Selbstfahrlafette 10.5cm was armed with Krupp’s 105mm K 18 L/52 gun with limited traverse of 8 degrees (left and right) and based on modified Panzerkampfwagen IV Ausf A‘s chassis – some sources mention Ausf E. The gun itself was developed by Krupp and Rheinmetall from 105mm sK 18 L/52 heavy field gun and was mounted with a muzzle break. The gun was capable of penetrating 111mm of 30 degrees sloped armor plate at 2000 meters. It was mounted in lightly armored (armor protection ranged from 10mm to 50mm), open at the rear superstructure. The layout of the armor protection made sides and rear vulnerable to the enemy fire and only allowed vehicle to be used with its front facing the enemy. For local defense single machine gun (7.92mm MG34) was carried inside the fighting compartment. Vehicle was powered by Maybach HL 120 TRM engine with total power of 300 horsepower (same as Panzerkampfwagen IV) allowing it to travel at the maximum speed of 40km/h.
Originally, two prototypes were assigned to Panzerjager Abteilung 521 in preparations for upcoming attack on Gibraltar – never realized Operation Felix. At the beginning of Operation Barbarossa in the Summer of 1941, both vehicles were assigned to 3rd Panzer Division and were troop tested. One of them was lost when its ammunition exploded (as reported it was then captured the Soviets) and the second one was brought back to the factory in the October of 1941. No serious technical problems were reported when vehicles were troop tested other than wear on steering brakes.
The further fate of the surviving vehicle is unknown, but it was probably taken apart at the Krupp factory.
Both prototypes proved to be very effective against Soviet KV series heavy tanks and T-34/76 medium tanks. Full scale production did not take place, while even limited numbers would prove to be very useful to the front line troops on the offensive and defensive, especially when faced with superior Soviet armor in 1941 and 1942.
In early May of 1942, a new design of Sturmpanzer, the Bär (Bear) was proposed. On March 4th of 1943, Krupp proposed development of new Sturmgeschütz armed with 305mm L/16 mortar and first drawings were ready in May. It was to be armed with a 305mm gun mounted in the superstructure, based on the modified chassis of the then new Panzerkampfwagen VI Tiger (Tiger I) heavy tank utilized some Panther components with new suspension developed by Krupp. The new vehicle was to weight 120 tons.
This new Sturmpanzer was to be powered by a 12-cylinder Maybach HL 230 P 30 engine producing 700hp. This would have al-lowed the vehicle to travel at a maximum speed of approximately 20km/h [12 mph]. Bär was to be armed with a rigidly-mounted 305mm KwK L/16 gun installed in an armored superstructure in the back of the hull. The main gun could only be elevated from 0 to 70 degrees and had a range of 10,500 meters [11,400 yards]. Each 305mm round weighed 350kg [770 pounds] and carried a 50kg [110 pound] charge. The interior storage space allowed for only 10 rounds.
Bär was to be 8.2 meters [26.7 feet] long, 4.1 meters [13.65 feet] wide and 3.5 meters [11.4 feet] high. Armor was sloped and protection ranged from 80mm on the sides to 130mm at the front. Sturmpanzer Bär was to be operated by a crew of six – commander, gunner, two loaders, driver and radio-operator. The project never left the drawing board, but was a step in the development of the Sturmtiger.
Sonderausführung des PzKpfw IV.
In late 1943, Zahnradfabrik Augsburg equipped normal (turretless) Panzerkampfwagen IV Ausf G/H with newly developed hydraulic steering system. Thoma (non-liquid) oil drive transmission was installed and drive sprocket was replaced with the new one. The power train consisted of twin oil pumps driven by Maybach HL 120 TRM engine. In order to accommodate all the changes, entire engine deck and rear was modified. In mid 1944, this prototype was fitted with modified hydraulically operated turret. Tests were carried on but were never concluded and for testing purposes the only prototype was send to Russia and served with the Waffen SS unit. At the end of the war, this vehicle was captured by the US Army and was sent to United States for further examination. Tests were never concluded and this vehicle is still at Aberdeen U.S Army Proving Grounds in Maryland.
Panzerkampfwagen IV mit hydrostatischen Antrieb at Aberdeen.
Photo provided by Alec Corapinski.