Saturday 27 January 2018

The Wasp and Its Sisters

Like other light tanks, the PzII chassis was actively used for the creation of SPGs. Thanks to larger dimensions than the PzI and a more powerful engine, it could mount a larger caliber gun. After conversion, the PzII chassis was ideal for the leFH 18 105 mm howitzer. This article will describe several SPGs on the PzII chassis, including the Wespe, a light SPG that helped a long obsolete light tank chassis remain in production until the summer of 1944.

Self propelled sIG 33, take two

Initially, the Germans didn't consider the PzII as a candidate for a 105 mm SPG chassis. In the summer of 1939, Krupp's engineers began working on an SPG designed for tank support. In the fall of 1939, the Pz.Sfl.IVb project appeared. The vehicle was rather good, so no plans regarding alternatives were considered.

On the other hand, experience from the campaign in Poland showed that infantry needs the mechanization of the 149 mm heavy sIG 33 infantry gun. Alkett, a subsidiary of Rheinmetall-Borsig AG, received an order to install the sIG 33 onto a PzI Ausf. B chassis in early 1940. The result was the 15 cm sIG 33 (mot S) auf Pz.Kpfw.I Ausf. B.

A lesser known fact is that Alkett also tried to install the sIG 33 onto a PzII chassis. The overall concept did not differ from the PzI vehicle. The work reached the prototype stage. Unfortunately, no photographs of this vehicle remain. All that is known is that the trials ended in failure. It is not clear what Alkett did wrong, but the SPG had a tendency to tip over when firing. It's likely that the wider tank did not allow the gun to rest on the fenders, so the bore axis was even higher than on the PzI vehicle.

Experimental prototype of the sIG 33 on a PzII chassis. In this case, the chassis only has five road wheels.

This explanation is backed by the fact that a converted vehicle went through trials in June of 1940. This time, the wheels of the sIG 33 were removed, but the mount was preserved. A significant reduction in the height of the bore axis meant that the tipping issue was resolved. This success became the starting point for further work.

A new SPG was submitted for trials in October of 1940. Alkett engineers tried to use the chassis of the PzII Ausf. C to the fullest. The fighting compartment width increased to the entire width of the vehicle. The driver's compartment was shrunken as much as possible, which allowed the gun to be positioned better.

Like last time, the sIG 33 was not changed at all, only the wheels were removed. German command considered it possible to remove the sIG 33 and replace the wheels in case the SPG broke down. There is some logic in this requirement, considering the experience with using the 15 cm sIG 33 (mot S) auf Pz.Kpfw.I Ausf.B. However, the massive mount consumed a lot of room in the fighting compartment, and the changes made to it didn't help much.

A production version of the 15 cm sIG 33 B Sfl.

It was decided to cease working on this SPG in February of 1941, but the idea remained. The Alkett design bureau received orders to develop a converted chassis. A pilot batch of 12 such SPGs was planned.

The reworked SPG was similar to its predecessor, but was much larger. The length of the hull increased from 4810 to 5480 mm, and the width from 2223 to 2600 mm. This forces some changes to be made to the chassis. In addition to adding another road wheel, the transmission had to be changed. The vehicle was powered by a V-8 Bussing-NAG L8V/GS 155 hp engine. This was its only application, as it was also used on German 4-wheel armoured cars. One of the reasons for using it instead of the Maybach HL 62 TR was its smaller length. Considering that the designers were tasked with maximizing the size of the fighting compartment, this was a reasonable change.

The fighting compartment. It is rather roomy, thanks to the lengthening of the chassis.

The work aimed at enlarging the fighting compartment gave fruit. The 15 cm sIG 33 B Sfl (149 mm sIG 33 gun B on self propelled chassis) could fit more than just the gun. The four crewmen were first class citizens. There was also space for ammunition. The SPG could only carry 10 rounds, but compared to the 15 cm sIG 33 (mot S) auf Pz.Kpfw.I Ausf.B, which could barely fit 3, this was a marked improvement. 

What's more important is that the height of the vehicle decreased compared to its predecessor. It was only 1980 mm tall, a little less than the PzII Ausf. C. The decrease in height improved the situation with stability during direct fire.

The same vehicle. It was destroyed by an ammunition rack detonation, which allows us to see inside the fighting compartment.

Alkett was loaded with requests, and the production of the pilot batch had to be delayed. The first 7 SPGs were delivered in December of 1941, the rest in January of 1942. By then, the PzII Ausf. F was in production. The SPG borrowed several hull elements from its design. All 15 cm sIG 33 B Sfl were sent to newly formed units: s.IG.Kp(Mot.S) 707 and s.IG.Kp(Mot.S) 708, six vehicles per battery. The organization of a battery was the same as the units that used the 15 cm sIG 33 (mot S) auf Pz.Kpfw.I Ausf.B. Since the onboard ammunition capacity was not high, the SPGs were supplied by Sd.Kfz.10 halftracks.

The driver received a separate cabin.

The 70th motorized sIG battery was the first to be sent to the front. This happened in February of 1942. The battery was sent to North Africa, where it was included into the 90th Light Division. This formally non-tank unit contained, for one, the 190th Tank Battalion since 1942. The practice of using motorized gun batteries in support of tank units did not change. The 707th battery was included into the 90th Light Division as well in April of 1942.

View from the front. The driver's hatch is visible. The observation device is different than the one used on the PzII.

The act of sending the 15 cm sIG 33 B Sfl raises many questions. The German command was very well aware of the issues experienced by the 15 cm sIG 33 (mot S) auf Pz.Kpfw.I Ausf.B in 1940 and on the Eastern Front. Of course, from a technical point of view, it was better than its predecessor, but not much. The mass of the 15 cm sIG 33 B Sfl was 16 tons, nearly twice as much as its predecessor. This was the heaviest vehicle on the PzII chassis. There is no such thing as miracles, and the price for this weight gain was reliability.

It's also not clear what German generals were thinking when they sent a direct infantry support vehicle to North Africa. It's quite hard to get up close to the enemy in terrain where the flora consists of nothing larger than a small shrub.

The gun at maximum elevation.

It's hardly a surprise that the 15 cm sIG 33 B Sfl became an unending headache for its crews. The SPGs began breaking down before they even saw combat. The 90th Light Division headquarters reported that both batteries were out of action by the end of May. The SPGs experienced constant engine trouble and overheating. There were some tricks that could be pulled with the engine, but there was nothing that could be done about the poor maneuverability. In other words, this vehicle was completely unsuitable for the North African theater. All of these issues were easily predictable, but this didn't stop the Germans in early 1942.

Unloading a 15 cm sIG 33 B Sfl, early 1942.

Thanks to its unusual form, the 15 cm sIG 33 B Sfl stands out in contemporary photographs. However, this form did not positively affect is worth in combat. In the rare cases where the SPGs were not being repaired, their contributions to battle were slight. Their main task was to support infantry, often by direct fire, for which their bulletproof armour was insufficient. It's not surprising that only 8 vehicles out of 12 remained by the end of October 1942.

The combat career of the 15 cm sIG 33 B Sfl ended with the British counteroffensive at El Alamein. By December 2nd, all vehicles of this type were lost, mostly for technical reasons. 6 SPGs were captured by the British. Later, several of them ended up in the Egyptian army. The last 15 cm sIG 33 B Sfl was destroyed in 1948 during the Israeli War of Independence.

The crew was increased to 5. They felt comfortable in the fighting compartment of the 15 cm sIG 33 B Sfl.

To wrap up, let us discuss an interesting fact to do with the name of the vehicle. The 15 cm sIG 33 B Sfl is often called Sturmpanzer II or Bison. In practice, neither name was ever used in regards to this vehicle. The SPGs did not live long enough to receive a "beastly" name.

The failure of the 15 cm sIG 33 B Sfl did not stop the Germans. The sIG 33 was installed on another tank, the Pz38(t). This was how the Grille SPG came to be. As for the PzII, it had another calling.

Howitzer support for tank divisions

The PzII received a second chance in the summer of 1942. This is largely caused by Krupp's failure. By then, the Pz.Sfl.IVa tank destroyer was completely rejected, and the fate of the Pz.Sfl.IVb was also not looking good. The vehicle, which was renamed to Pz.Sfl. leFH 18 Ausf.A in 1942, was very difficult to put into production. Krupp's SPG also fared poorly in the department of parts commonality, which was a significant drawback in times of war.

Another problem was that the OKH changed its requirements for "self propelled gun mounts". Now the gun had to come off for installation on a towed platform, like on the 15 cm sIG 33 B Sfl. In addition, the turret had to allow for 360 degree fire. All of this meant that the work on the vehicle would take even longer.

The first leFH 18/2 (Sf) auf GW II prototype.

The OKH began to suspect that, at this rate, they would not receive an SPG until the end of the war. A program to develop a temporary solution was launched. Porsche's tank commission (Panzerkomission) supervised this project. Quickly getting their bearings, the commission chose the PzII as a chassis for the 105 mm leFH 18 howitzer. This time, the chassis would retain its initial layout. Successful experience in using the Lorraine 37L tractor as an SPG chassis showed that a roomy fighting compartment can be obtained even with a small chassis. Alkett, the company that converted Lorrain 37Ls into SPGs, was chosen as the developer.

The same vehicle from another angle. The driver's cabin differs noticeably from the production variant.

The experimental prototype, indexed leFH 18/2 (Sf) auf GW II (self propelled leFH 18/2 howitzer on the GW II chassis) was built quickly. When designing the GW II, Alkett's engineers tried to change the initial vehicle as little as possible. The suspension and transmission were left without changes.

The engine compartment was radically changed. It was removed from the rear of the hull. The engine and the cooling system were moved to the center. The driver's compartment was cut off from the rest of the crew, and the driver received a small cabin. The upper front plate was removable, and the driver's cabin came off with it. Alkett later used the same layout when designing the Hummel SPG.

Engine, transmission, gun, and fuel tank layout.

Thanks to this rearrangement, the rear of the SPG now had enough room for a fighting compartment. A gun crew of three men was placed in an open top casemate. The oscillating part of the leFH 18/2 gun, covered with a gun shield. was placed above the engine compartment. The ammunition capacity consisted of 30 rounds, which was sufficient for a fighting vehicle of this size.

The drawbacks of this tight layout was the difficulty in servicing the engine and cooling system. Like in the Hummel, this necessitated the removal of the gun, then the front of the casemate and engine compartment roof. Even though a relatively large gun was installed on this chassis, the mass didn't increase that much, only to 10,800 kg. Overall, its mobility remained on the same level with the PzII.

leFH 18/2 howitzer mount and the engine compartment roof.

The first trials of the leFH 18/2 (Sf) auf GW II showed that the tank commission made a good choice. It was no secret that this was not a proper replacement for the Pz.Sfl. leFH 18 Ausf.A. However, most importantly, it didn't take much time to put the light SPG into production, since its chassis was already being produced, and it cost a lot less. On July 25th, Hitler was informed that a self propelled howitzer on the PzII chassis is quite possible. Trials of the prototype confirmed this. This success was fatal for the  Pz.Sfl. leFH 18 Ausf.A. The idea of a medium self propelled gun mount was not discarded, but mass production was out of the question.

The fighting compartment was relatively roomy.

As with the Hummel, there were no plans to produce the leFH 18/2 (Sf) auf GW II at Alkett. The factory was completely occupied with the production of the Stug 40. It was reasonable to task factories that produced the PzII with making an SPG on its chassis. Tanks of this type were produced at FAMO in Breslau and Ursus in Warsaw. After July of 1942, the primary product of these factories was the Pz.Kpfw.II als Sfl. Mit 7,5 cm Pak 40 tank destroyer. Preparation for production of the leFH 18/2 (Sf) auf GW II began in late 1942. Compared to the experimental vehicle, the production vehicle had a different driver's cabin, leFH 18/2 muzzle brake, and stowage.

Getting to the engine was no simple task.

Initially it was planned that the first production SPGs would be built in January of 1943. These plans were changed since FAMO and Ursus received a large order for tak destroyers, producing 80 Pz.Kpfw.II als Sfl. Mit 7,5 cm Pak 40 in January. The first two leFH 18/2 (Sf) auf GW II were only built in February. Real mass production began in March, when both factories built 30 SPGs. The peak of production was reached in April: 136 SPGs. No records were set after that, since the first few months of production met the demand for this vehicle. 517 SPGs were built in 1943 overall.

The leFH 18/2 (Sf) auf GW II was given the name Wespe (wasp) in 1943. Even though it was officially rescinded in February of 1944, the name remained in use, both in official and unofficial documents. In total, the vehicle changed its name 5 times. This situation was not uncommon for the Germans.

GW fur Munition ammunition carrier. It differed little from the SPG. If necessary, it could be converted into an SPG.

It was clear that the Wespe would not do on its own by the spring of 1943. The small ammunition capacity forced the military to begin development and production of munitions carriers. These vehicles were called Munitionsfahrzeuge (later GW II fur Munition). Their number was to be one quarter of the overall number of SPGs produced.

Like the munitions carrier for the Hummel, the GW II fur Munition had few differences from its SPG variant. It had no gun, and the gun opening was closed off. In case of necessity, it was relatively simple to transform it into a Wespe. The first 10 carriers were built in June of 1943, and 104 were completed by the end of the year. Most of the responsibility for producing SPGs and munitions carriers fell to Ursus. FAMO changed fully to producing Sd.Kfz.9 halftracks in August of 1943.

Captured Wespe with the personal name "Prag". Today it can be seen in Patriot park.

The SPGs were sent to light SPH batteries, introduced in TO&E K.St.N.431b issued on January 16th, 1943. Each battery had 6 Wespe, a PzIII artillery observer tank, and a light Sd.Kfz.250/5 halftrack. Later, 2 munitions carriers were included into the structure. Self propelled artillery squadrons included two Wespe batteries and one Hummel battery.

The light SPGs were supposed to be assigned to tank divisions, but in reality they were distributed otherwise. As of June 1st, 1943, only the 17th Tank Division had two Wespe batteries. The 3rd and 29th Panzergrenadier divisions received 3 batteries each. The same amount ended up in the Grossdeutschland division. SS divisions Das Reich and Leibstandarte received two batteries each. By July 1st, 8 more tank divisions, two Panzergrenadier divisions, and the SS Totenkopf division received Wespe batteries.

The 10800 marking indicates the mass of the vehicle.

A significant amount of these vehicles took part in the Battle of Kursk. Overall, the combination of the Wespe and Hummel in one unit was considered successful. On the Eastern Front, the light SPGs proved themselves reliable. Most complains were about defects in the function of the brakes and turning mechanisms, which were subjected to extra stress.

Different reviews came from Italy. The vehicle was too slow and its engine too weak for mountainous terrain. Suspension issues also plagued the SPG. The Hummel experienced similar issues. This theater required a different kind of vehicle. However, in places where driving in the mountains was not necessary, the Wespe showed itself well. Unsurprisingly, this SPG was used by all German tank divisions, five grenadier divisions, and six SS divisions by the end of 1943.

This vehicle fought in the Battle of Kursk and was captured in late 1943.

The good initial design meant that there were few modernizations introduced during the Wespe's service life. Most significant changes were introduced in June of 1943, when the right headlight was removed, suspension reinforced, and modernized deflectors added, three per side. The deflectors were once again reinforced in November of 1943.

Production continued until June of 1944. Overall, 676 Wespes and 159 munitions carriers werebuilt. Their serial numbers fell into the 31001-31300 and 21651-32185 ranges. Production didn't end because the vehicle was obsolete, but because the front line drew too close. After a series of successful offensives by the Red Army in 1944, the factory in Warsaw was threatened.

Tactical markings were applied to the front fenders. If you look closely, you can see a divisional marking on the right fender.

Despite the Germans suffering heavy losses in 1944, the number of SPGs in use remained high. The peak was reached in 1944, which 445 Wespes were listed in service. From then on, the number decreased, until only 352 Wespes were left at the end of the year. 169 SPGs remained in service by March 15th, 1945, a quarter of the total production.

Wespes knocked out near Zhitomir, 1944.

5 Wespes survive to this day. One of them can be seen in Patriot park. This SPG with serial number 31081 was built in April of 1943 and sent to the Das Reich division. It had a personal name: "Prag". The vehicle fought at the Battle of Kursk and was captured in late 1943.

SPG with a Heuschrecke 10 type turret. Development did not move past the production of a model.

To finish off, let us mention one more SPG on this tank chassis, which was also to be armed with a 105 mm howitzer. During the development of the Heuschrecke 10, a similar vehicle was designed on the PzII chassis. Instead of a casemate, a turret platform and a turret were installed on a lengthened chassis. A special mechanism allowed the turret platform and turret to be set on the ground without an external crane. Unlike the Heuschrecke IVb, which was built, the analogous design on the PzII chassis never made it past a draft project and a model.

1 comment:

  1. I have been trying to find the layout of the engine and fuel tank forever! Thank You!