15 cm sIG 33 (Sf) auf Panzerkampfwagen I Ausf B

The 15 cm sIG 33 (Sf) auf Panzerkampfwagen I Ausf B, unofficially called the Sturmpanzer I Bison, was a German self-propelled gun of the Second World War. After the invasion of Poland showed that towed heavy infantry guns could not keep up with tanks, a 15 cm sIG 33 howitzer was mounted, with its carriage and wheels, on a Panzer I Ausf. B chassis in place of the turret and superstructure. Thirteen millimetre plates formed a tall, open-topped fighting compartment that shielded little more than the gun and gunner, and there was no room for ammunition. Alkett converted 38 vehicles in February 1940. Thirty-six of them served in six heavy infantry gun companies with Panzer divisions in the Battle of France and later in the Balkans and the Soviet Union. The overloaded chassis broke down often, and its great height was a serious tactical drawback.