The first self-propelled artillery in German service
In 1939, the Panzer III was already in full-scale serial production, as was the Panzer IV. Older transitional models were, thus, no longer needed for first line operations. So, the Panzer I Ausf.B chassis was chosen to test some more useful conversions. One of these was based on the Czech 47 mm (1.85 in) gun, by then largely available, which became the first German tank hunter, the Panzerjäger I.
15cm sIG 33 (sf) auf Geschüetzwagen I Ausf B (Bison) prototype
A second conversion was born from the demand for a close-support howitzer carriage for the infantry. In fact, this request was found in reports after the campaign of Poland, which highlighted the lack of heavy artillery support, which was unable to cope with the fast pace of the Panzers. And so, in order to motorize artillery companies, an armored self-propelled carriage was needed. Many unused Panzer I Ausf.B, the sturdiest of this first series, were available. A prototype was conceived by Alkett in a short time and proved that the concept had some merits.
Basically, the standard sIG 33 150 mm (5.9 in) field howitzer, was mounted, via ramps, on two receiving rails with fixations, and two “baskets” for each wheel, which held the entire gun, on top of the chassis, with its upper hull and turret removed. This configuration allowed the gun to be put in place and removed quickly, but it was also a radical solution, imposing very tall profile, with 13 mm (0.51 in) bolted armored plates forming the open-top fighting compartment. It was also open to the rear, to allow the loaders to move around, but protection was henceforth limited to the gun and the gunner only.
Pointing was made by the means of a Rblf36 sight. The mount allowed 25° of traverse with an elevation from -4° to +75°. There was no room onboard for ammunition, which had to be towed separately by another vehicle. Thirty-eight in all were produced in February 1940 by Alkett, officially named the 15 cm sIG 33 L/12 (Sf) auf Geschüetzwagen I Ausf.B.
A wooden frame and winch system was used to load the 15 cm s.I.G 33 gun onto the tank chassis
It was first deployed during the French campaign, serving in the schwere Infanteriegeschütz-Kompanies 701 and 706, affected to various Panzerdivisions. They all survived this campaign, and later saw action during the campaign of the Balkans, in Yugoslavia and then in Greece.
In June, they were all redeployed to Romania, to be ready in time for Operation Barbarossa. But only two groups survived, the 705th and 706th belonging to the 7th and 10th Panzerdivisions. Few survived Operation Barbarossa and the remaining unit, the 701st, participated in operation Fall Blau, early 1942. They fought until 1943 and the last Bisons were seen in the depleted 704 unit, affected to the 5th Panzerdivision.
During these years, their limitation has became obvious. They suffered from breakdowns due to a serious overload of the chassis, a very tall superstructure, impossible to miss, and lack of protection for the gun crew. Plus, these machines were dependent on their ammunition vehicles. On the bad roads of Russia and in particular Ukraine, this proved fatal. However, this experience helped to Germans to successfully conjure up other sturdier platforms to carry their standard howitzer.
The 15cm sIG 33 (Sf) Geschüetzwagen I Ausf B is often called the ‘Bison’. It was not known by that name during WW2. It was a name given to it after the war and used by model kit companies. It is also known as the ‘Sturmpanzer I’ an assault tank. This name is not correct as it did not have enough protective armour to protect the crew from anything other than small arms fire so it would be easy to knock out during an assault on the front line. This vehicle was a self-propelled artillery gun designed to fire high explosive shells over the heads of friendly troops and tanks into the ranks of the enemy at long range.
German Army vehicles fitted with the artillery howitzers were called a ‘Geschuetzwagen’, which is literally translated as a ‘gun vehicle’. The letters ‘SF’ stand for ‘Selbstfahrlafette’ – self-propelled carriage. It has also been called a ‘Waffenträger’, a weapon carrier, as the 15cm howitzer could be dismounted. To make things even more confusing it is also referred to as the 15cm sIG 33 (Sf) Panzerkampfwagen I Ausf B or 15cm sIG 33 (Sf) PzKpfw I Ausf B. You can understand the need to find a short name to identify this SPG. This is why the word Bison was introduced after the war. It was given the nickname Bison because of its bully appearance.
The abbreviation sIG is short for schwere Infanteriegeschuetz which translated means heavy infantry gun.
Links and resources
sIG 33 Bison specifications
|Dimensions (L-W-H)||4.67m x 2.06m x 2.80m
(15’3″ x 6’8″ x 9’2″ ft.in)
|Total weight, battle ready||8.5 tons (17,000 lbs)|
|Crew||4 (driver, commander, gunner, loader)|
|Propulsion||Maybach 6-cyl NL38TR water-cooled, gasoline, 100 bhp|
|Armament||sIG 33 15 cm howitzer (5.9 in), 30 HE rounds|
|Armor||From 5 to 13 mm front (0.2-0.5 in)|
|Speed (on/off road)||40 km/h (25 mph)|
|Range||140 km (87 miles)|