wooden mock-up of the second variant of the Krupp self-propelled gun known as Grille 12; the beams lying on the track mudguards were used to lower the weapon from the chassis and place it in a static firing position, source: Flickr.com with permission of the publishing user, edited

Long before they fielded their first actual Panzer divisions, the Germans were clear that artillery had to be an integral part of them. Theoretical studies and improvised exercises with various mock-ups had conclusively confirmed that tanks simply could not manage without artillery support. Classical guns towed by horses, lorries or later half-tracked prime movers, however, could not keep pace with fast armoured formations. Representatives of the armoured arm therefore turned to the army's Waffenamt with a requirement to develop so-called Selbstfahrlafetten — self-propelled gun carriers. The tankers wanted an artillery weapon that would be fast, capable of cross-country travel and always ready to open fire immediately. Self-propelled guns were never intended to lead the attack — they were to stay close behind the attacking tanks, but behind them nonetheless. This meant they would not come into direct contact with the enemy and therefore did not need particularly heavy armour. Speed and firepower were what mattered.

Waffenamt Requirements

The task of specifying requirements for new weapons for the German army, negotiating with suppliers and handling related matters fell to the Waffenamt. Within the office, responsibilities were further divided between individual departments. Tank development and related equipment, for example, fell under Waffen Prüfwesen 6 (abbreviated WaPrüf 6), while artillery weapons — which officially included self-propelled guns — came under Waffen Prüfwesen 4 (WaPrüf 4). The representatives of this department decided they would not simply parrot whatever the tankers told them, but would inject their own ideas into self-propelled gun development and do things, at least partly, their own way. Unfortunately, WaPrüf 4's vision of how artillery weapons should be used was somewhat reactionary. The department's representatives still regarded a gun as a weapon which, thanks to its long range, could fight effectively from a single position without constantly changing location. They therefore considered the combination of a prime mover and a towed gun a more efficient solution than a true Selbstfahrlafette.

Development of the first fully capable self-propelled gun, the Geschützwagen IVb für 10,5cm leFH 18/1, or Sd.Kfz. 165/1, had been initiated before the war, but due to the constant stream of change requests from the Waffenamt it dragged on until the end of 1941. And even after all those modifications, improvements and design tweaks, WaPrüf 4 remained dissatisfied and had the promising self-propelled gun "buried." During the first years of the war the German army therefore had to make do with more or less improvised self-propelled guns based on the chassis of already obsolete light tanks. It was not until the spring of 1942 that WaPrüf 4 launched an ambitious programme to develop advanced-design self-propelled guns that were to become the artillery backbone of the German Panzer divisions. The programme encompassed a whole family of self-propelled guns designated Heuschrecke and Grille. Regrettably, WaPrüf 4 embedded some of its misguided ideas about what a modern self-propelled weapon should look like into this programme as well.

another view of the Krupp Grille 12 wooden mock-up; the side panels around the fighting "turret" are folded down and the gun is prepared for indirect fire, source: Flickr.com with permission of the publishing user, edited

Specifically, the Waffenamt demanded unlimited horizontal traverse of the weapon and the ability to remove the gun from the vehicle easily and then use it independently in a static firing position. WaPrüf 4 took the view that if the gun could be removed from the self-propelled mount in the field and used on its own, the carrier vehicle could drive elsewhere — meaning it would no longer present the same target as the gun itself, would not suffer stress and wear during firing, and could in the meantime perform other tasks such as fetching additional ammunition. The representatives of the armoured arm must have been tearing their hair out in despair, because this ran directly counter to their vision. Self-propelled guns were supposed to be self-propelled so that they could move — not so that they could stand still. WaPrüf 4, however, got its way.

Types Under Development

The competition for the new self-propelled guns was opened to Krupp and Rheinmetall-Borsig in the spring of 1942. A total of three self-propelled gun types were to be developed, armed with guns of 105, 128 and 150 mm calibre. Following a conference held in early June 1942, it was settled that the vehicle with the light 105 mm howitzer would use the chassis of the then-under-development Leopard tank, while the heavier 128 and 150 mm guns would use the chassis of the equally still-under-development Panther. Following this decision, Krupp asked the Waffenamt for the detailed technical documentation of the Panther to be supplied as quickly as possible so its engineers had something to work with.

Krupp Heuschrecke

In July 1942 Krupp presented the Waffenamt with its first drawings of the 128 mm and 150 mm self-propelled guns. The first was given the working designation Gerät 5-1211 (12.8 cm K43 (Sfl.) Kp.I) and was armed with the K43 gun; the second was designated Gerät 5-1528 (sFH 43 (Sfl.) Kp.I) and was to carry the heavy howitzer sFH 43. Both projects were also given the cover designations Heuschrecke 12 and Heuschrecke 15 (Heuschrecke = grasshopper). Krupp then set to work on full-scale wooden mock-ups of both vehicles. In September 1942 Krupp proposed that the light 105 mm howitzer version should also be based on the Panther chassis (rather than the Leopard as originally planned). This may have been connected to a significant revision of the proposed Leopard tank design that was decided upon in September 1942. Krupp promptly prepared a simplified wooden mock-up to show what the installation of the light howitzer on the Panther chassis would look like.

wooden mock-up of the light 105 mm self-propelled howitzer on the Leopard tank chassis, source: Flickr.com with permission of the publishing user, edited

Waffenamt representatives inspected the wooden mock-ups of all vehicles, probably in October 1942, and subsequently presented the manufacturer with a list of change requests. These included, for example, reducing the firing height, replacing the gearbox with a different type, and so on. In addition, the officials recommended using armour plate made of steel produced in Siemens-Martin open-hearth furnaces rather than the higher quality but more expensive steel from electric arc furnaces. What troubled the WaPrüf 4 officials most, however, was the fact that while the proposed vehicles did allow the weapon to be removed from the chassis, they could not do this under their own power. The procedure required a lifting device that had to be transported by a separate accompanying vehicle — something the department found most unsatisfactory.

The designers countered that lowering the gun and setting it on the ground required three massive beams, each weighing 400 kg, and there was simply nowhere on the vehicle itself to carry them. The only feasible solution was to stow the beams on the track mudguards. This was obstructed, however, by the sloped side armour of the hull — to create sufficient space above the tracks, the hull side armour would have to be vertical rather than sloped. The Waffenamt apparently saw no problem with this and asked Krupp to implement the design change. It is almost astonishing what WaPrüf 4 was willing to sacrifice for its misguided objective: this particular change to the hull design would certainly have significantly increased the cost of manufacturing the future vehicle.

It should also be noted that on 3 December 1942 the Waffenamt officially rejected Krupp's proposal to base the light 105 mm self-propelled howitzer on the Panther chassis. WaPrüf 4 confirmed that this vehicle was to be derived from the Leopard tank as originally planned. Just one month later, however, in January 1943, the Leopard tank project was cancelled — and the development of the light self-propelled gun on its chassis had shortly thereafter to be abandoned as well.

Krupp proposed using the Panther tank chassis for the light 105 mm howitzer and prepared this simplified wooden mock-up — but the proposal was rejected by the Waffenamt, source: Flickr.com with permission of the publishing user, edited

Krupp Grille

Based on the Waffenamt's change requests, the manufacturer prepared revised designs for the 128 mm and 150 mm self-propelled guns. To distinguish them from the first version, the code Kp. II Panther (presumably Krupp II) was added to their names — specifically Gerät 5-1211 (12.8 cm K43 (Sfl.) Kp.II) and Gerät 5-1528 (sFH 43 (Sfl.) Kp.II). The cover designations of both vehicles were changed for the second variant from Heuschrecke to Grille — thus Grille 12 and Grille 15 (Grille = cricket). At least for the Grille 12, a wooden mock-up was again built, and the surviving photographs of it give us a clear picture of the vehicle's intended appearance. Krupp positioned the fighting compartment at the rear of the vehicle. It is not entirely clear from the sources whether this necessitated moving the engine further forward (which seems probable).

The gun was mounted on a fully rotating "turret." The word turret is intentionally placed in quotation marks here, because in reality this was more of a large gun shield. The original plans reportedly did envisage a proper, fully enclosed fighting turret. As development progressed, however, it became evident that such a turret would simply be too heavy — especially once the Waffenamt imposed the requirement to use the cheaper open-hearth furnace steel. To achieve the same level of protection, walls made from this type of steel had to be thicker, which of course increased the weight of the armour plates. In the end the "turret" remained completely open at the rear, which is why it is more accurate to speak of a gun shield.

The gun itself stood on a rotating mounting and the armoured shield rotated with it. Placing the weapon at the rear of the vehicle was apparently motivated by the desire to make its removal straightforward. As surviving drawings show, the gun mounting was to be fitted with "wheels" allowing it to be rolled down to the ground along a ramp placed against the rear of the vehicle. This ramp was formed by the already mentioned beams, which the vehicle carried on its track mudguards (a third beam was apparently stowed on the hull rear). Lowering and raising the gun with its mounting and the entire armoured shield was handled by a winch mounted on the hull roof in front of the weapon. The lowering ramp was probably formed by only two beams; placing the weapon on the ground required all three beams, which were assembled into a star-shaped ground base. Exactly how the gun was then handled on the ground (placed on the tripod base formed from the beams) is not clear from the literature, though it was certainly no easy task.

the competing 128 mm self-propelled gun design by Rheinmetall-Borsig provided for the weapon to be lowered sideways; shown here is its wooden mock-up, source: Flickr.com with permission of the publishing user, edited

The wooden mock-up of the second Grille 12 variant was completed in November 1942 and presented to Waffenamt representatives in January 1943. The officials were apparently now satisfied, and at the end of January 1943 production of Grille 12 and Grille 15 prototypes was officially ordered. Krupp stated on this occasion that if it received the necessary Panther tank components by 1 May 1943 it would be able to complete its prototypes by September of the same year. While the prototypes were to be built using Panther components, future series production was intended to be based on the chassis of the planned Panther II — though that was still music of the very distant future.

In March 1943 a fundamental problem arose concerning the Grille 15. This self-propelled gun was to be armed with the newly developed sFH 43 howitzer in 150 mm calibre. Development of this weapon was running behind schedule, however, and the Waffenamt therefore asked Krupp to investigate whether the Grille 15 could instead carry the older sFH 18 howitzer of the same calibre. Krupp rejected this change as impractical. Further problems were not long in following. MAN was unable to deliver the required Panther components on time, with the result that by September 1943 not even a single prototype of either of the two new self-propelled guns was anywhere near ready. On 20 October 1943 WaPrüf 4's patience ran out and it officially ordered Krupp to cease work on both the Grille 12 and Grille 15 projects. Krupp complied, but continued theoretical studies on Panther-chassis self-propelled guns of its own accord until September 1944, when it was informed that the army was no longer interested in any such vehicles.

Rheinmetall-Borsig

How did the competing firm Rheinmetall-Borsig fare in the programme? It too submitted its first drawings in July 1942, under the designations Gerät 5-1213 (12.8 cm K43 (Sfl.) Rh.B.) and Gerät 5-1530 (15 cm sFH 43 (Sfl.) Rh.B.). As these complicated names suggest, the armament was identical to that of the Krupp vehicles — the K43 gun and the heavy howitzer sFH 43 respectively. Rheinmetall also received so many change requests from the Waffenamt that it had to prepare second-version designs in January 1943.

a later Rheinmetall-Borsig design for a 128 mm self-propelled gun designated Skorpion, which was to have had a very unconventional muzzle brake design; shown here in an artist's impression by Jaroslaw Janas, source: Jaroslaw Janas, edited

Unlike the competition, the Rheinmetall designers positioned the weapons in the centre of the vehicles. The gun was therefore to be lowered to the ground not rearward but sideways. The gun with its mounting and shield was again to be lowered down a ramp, but this time one placed against the side of the vehicle. The armour surrounding the gun was also open at the rear here, making it again more properly described as a gun shield than a full fighting turret. Rheinmetall promised delivery of the first functional prototype as early as August 1943, provided it received the necessary Panther components no later than 1 April of that year. Neither deadline was met.

Since they could not move on to building an actual vehicle, the Rheinmetall designers at least continued working on further paper proposals for a new self-propelled gun. In April 1943 they prepared drawings for an improved 128 mm self-propelled gun, which they gave the "tough-sounding" designation Skorpion (scorpion). This vehicle was to feature a completely unconventional muzzle brake consisting of what appeared to be three funnel-like chambers. After the project was cancelled, Rheinmetall prepared several further proposals for other self-propelled guns on the Panther chassis before definitively ending these activities, apparently in September 1944.

Conclusion

The enormous amounts of time and money invested in the projects described above ultimately came to nothing. The German army remained dependent until the end of the war on the "temporary" self-propelled guns Wespe and Hummel, which had originally been introduced only as an interim solution, pending the availability of the more advanced Heuschrecke and Grille fighting vehicles.

ARTICLE
CONTENTS:

WAFFENAMT REQUIREMENTS

TYPES UNDER DEVELOPMENT

KRUPP HEUSCHRECKE

KRUPP GRILLE

RHEINMETALL-BORSIG

CONCLUSION