Sturmpanzer II Bison(Self-Propelled Heavy Infantry Gun)

Even before Sturmpanzer I entered service, plans were made to develop improved version based on PzKpfw II's chassis and components. Panzerkampfwagen II became obsolete in 1941, but large number produced made it a perfect base for conversions. First improvised prototype was tested at Kummersdorf on June 13th of 1940. In October of 1940, Alkett completed first prototype based on Panzerkampfwagen II Ausf B's chassis, which did not provide adequate space for the large gun as well could not absorb the recoil.

Sturmpanzer II Prototype
Two types with different gun shield were produced.

On February 18th of 1941, it was decided to built Sturmpanzer II on modified and turretless chassis/hull of Panzerkampfwagen II. In July/August of 1941, first Sturmpanzer II Bison (lenghtened version) was produced. By January of 1942, total of twelve (versuchserie - trial series) was produced by Alkett - 7 were produced in 1941 and 5 in 1942.

Chassis was slightly widened (by 32cm) and lenghtened (by 60cm) in order to make room for the gun and additional sixth roadwheel was added. For vehicle being based on Panzerkampfwagen II , it had only few components in common with the base tank variant. It was powered by Bussing-NAG engine instead of regular Maybach. Unlike the Wespe, there were no protecting sides along the entire length of the superstructure. 150mm sIG 33 L/11.4 heavy infantry gun was mounted in the shield that extended straight across the full width of the superstructure. The gun had a range of 4700 meters and could be elevated vertically by 75 degress. The main armament could be used as a heavy infantry gun or as a heavy mortar, depending on the elevation and initial speed of the projectile. Sturmpanzer II was operated by the crew of 4 (commander, two gunners and driver) and it weighted approximately 16 tons. Its performance was poor as its weak engine overheated and vehicle had poor maneuverability.

Sturmpanzer II Bison in North Africa.