SARL 42

Vichy France (1940-1942)
Cavalry Tank – Project Only

The French Republic had one of the largest tank industries in Europe and the world during the interwar era, manufacturing a variety of armored vehicles designed for a range of purposes. One of these was the Somua S35 cavalry tank, produced for the French cavalry from 1936 onward. The S35 was a three-man cavalry tank using cast construction with a fairly thick 40 mm of maximum armor and a 47 mm SA 35 anti-tank gun. Despite being one of the more modern and potent French types in service by the campaign of May-June 1940, the S35 was also on its way out from the production lines, with its evolution and successor, the S40, being about to enter production (about 440 Somua S35s were manufactured, with the S40 being scheduled to replace the S35 from the 451st tank onward). This S40 was, in some ways, both a considerable evolution and a very similar vehicle to the S35. It adopted a modified suspension, with a raised front drive sprocket, in order to give the tank better cross-country capacities – the Achilles heel of the S35’s mobility – as well as a slightly lowered front hull. Outside of 80 of the first S40s, which were to keep the APX 1-CE turret, it would also use a new turret, the still single-man welded ARL 2C. At the same time though, much of the vehicle’s core characteristics remained the same – the crew complement, armor layout, armament and powerplant (though, at some point during production, the S40 was to switch from the S35’s 190 hp engine to a more powerful 220 to 230 hp version).

The German invasion during spring 1940 cut the production of the Somua tanks short, weeks before the first S40 would have left the factories. The installation of the Vichy Regime from late June 1940 onward, as well as the armistice of Compiègne and the drastic limitations installed upon the French military and its industrial complex, would, in appearance, almost entirely stop France’s tank manufacturing efforts. Only some very limited official studies, sponsored by the Axis, would remain in existence – for example, projects of improved S40 tanks with two or three-men turrets destined for Axis export, which were in the works at FCM. As with interwar Germany though, French military men and engineers were not all keen to respect the humiliating armistice. As early as 1940, some partially completed S40 hulls were hidden before the Germans could find them and likely completed by a secret service of Vichy’s military dedicated to armament gathering and construction, the CDM (Camouflage du Matériel/ Equipment Camouflage). At the same time, a project for a vastly remodelled model of Somua’s cavalry tank, taking lessons from the 1940 campaign, was starting to rise. It appears to have had some links to the CDM, which worked alongside this bureau, and was likely in some way part of this broader organization.

AMX, ARL, Somua: A varied shadow design bureau

A variety of engineers formed the rather obscure bureau which worked on what would be the new version of France’s late 1940s cavalry tank. Though the structure of this bureau is still little known to this day, it is known to have included engineers from both the state bureaus of AMX (Atelier de Construction Mécanique d’Issy-Les-Moulineaux) and ARL (Arsenal de Rueil), as well as from Somua, a private firm (subsidiary of the larger Schneider), which was quite obviously involved, as the tank would be a development of its own work. That being said, the core of the bureau and its key engineers appear to have come from the state bureaus rather than from Somua. The most important and well-known engineer involved was ARL’s Lavirotte, leader of the project and previous leading figure of the B1’s evolutions, the B1 Bis and B1 Ter, as well as the short-lived B40 project. At his side was another former engineer of ARL who had worked under Lavirotte, Hubert Clermont, who communicated most known information on the SARL 42 project through correspondence in the 1990s. The engineers working on the project no longer had their status as employees of ARL or AMX, being as civilian as one may be in theory. The project was undertaken without the knowledge of not only the German armistice commission tasked with ensuring the compliance with the terms agreed to at Compiègne, but also from the higher-ups of the Vichy Regime and the military. Indeed, the idea behind this “shadow tank” would be to use it, in one way or another, as a way to resist German invaders in the future – not as a way to bolster the Vichy Regime in its limited operations against the Allies.

How to improve upon the Somua ?

In order to design the new cavalry tanks, lessons were taken from the Battle of France, and the drawbacks faced by French tanks during the campaign. The Somua S35 is generally considered to be one of the French tanks which fared the best, but this is not actually saying much, seeing as much of the fleet consisted of desperately under-armed, undermanned, and slow light infantry tanks, as for example the R35. In the case of the S35, the one-man turret, as on the vast majority of French tanks, proved to overtask the commander way too much, impeding the situational awareness, reaction time, decision-making and gun operating of the vehicle. This was, far and wide, the greatest issue with the vehicle. Outside of this, the 47 mm SA 35, while very much satisfactory by 1940, also likely grew obsolete in the following years, and the S35’s suspension proved too low, reducing the vehicle’s cross-country capacities – an issue already tended to in the incoming S40.

The project for a new cavalry tank took the S40’s hull as the basis. In comparison to the S35, it featured a raised front drive sprocket, which would already improve crossing capacities and all-terrain mobility. The most important change the tank would have to undergo would be a much larger turret, able to accommodate both a 75 mm gun, which could adequately target both armor and infantry, as well as a crew large enough to operate the vehicle in decent conditions.

This improved cavalry tank was given the designation of SARL 42 – SARL stood for Somua Arsenal de Rueil (the Somua & ARL bureau, the most heavily involved company in the project), while 42 refers to 1942, when the project, which appeared to have started in the late summer of 1940, reached maturity, at least in terms of design.

The project was undertaken in secret and, as such, with high constraints. The plans had to be prepared to be hidden very quickly in case of a ‘visit’ by the Armistice commission or Vichy higher-ups, and the engineers had to keep as low of a profile as possible, communicating for example though traveling or secret correspondence, but as little as possible by more official or traceable means. In the beginning, Clermont had to gather plans for the S40 hull by communicating with Somua’s facilities at Saint-Ouen, which would then be used to work on the SARL 42.

Designing the hull

The hull was the element of the SARL 42 which would require the least major changes, though that is partially by virtue of the tank’s turret being entirely new.

Upon the start, it appeared clear that the SARL 42’s hull would be directly based on the S40, however, this does not mean a variety of different configurations were not studied. The most significant subject of debate appears to have been the length of the hull. Five different silhouettes, different only in length, were proposed, the shortest 5 and the longest 5.3 meters long. The length eventually settled on was 5.42 m – the same as on the S40, likely to simplify the production of this new hull. The suspension would therefore have been the same as on the S40, itself very similar to the S35’s but with a raised drive sprocket. Ten road wheels would be used, with the suspension generally being very close to Skoda’s LT vz.35 in design (not a surprising fact considering Schneider, Somua’s mother firm, collaborated closely with Czechoslovak industrial firms, Skoda notably).

Significantly enough though, the SARL 42 was to use a welded hull design instead of the previous casting. This was a significant evolution, a testimony to the modernity of welding. This also changed the silhouette of the vehicle to an extent, highly reducing the number of rounded shapes on the hull. The upper front plate was made purely straight on the SARL 42. To the left of the vehicle, the driver’s post stuck out of this front plate quite considerably and featured a large frontal vision hatch as well as side vision ports.

Fairly forward in the hull was the turret ring. This was a larger turret ring than on previous Somua tanks, as wide as 1730 mm, in order to accommodate a much larger turret. With a width of 2.28 m, the vehicle was somewhat widened from the S35 and S40’s 2.12 m in order to accommodate this turret ring. As for the height of the hull, it was 1.71 m.

The engine compartment was 1.88 m long. The engine which was to be fitted in the SARL 42 appears to have been the definitive model of the Somua engine already fitted in the S35. In this form, it would be an 8-cylinders, 13,745 cm3 engine producing up to 230 hp at 2,200 rotations per minute, though, at the standard 2,000, it would produce 220 instead. This engine was already scheduled to be installed in the S40, though not on the first examples.

As for armor layout, it appears the SARL 42 would have retained one very similar to the Somua S35 and S40. The hull front would be 40 mm thick, the sides 20 mm, and the rear 30 mm. The tank would lose some of the rounded shapes of casting, but the better structural resistance of welding in comparison to casting would likely compensate for this, with the armor being likely very close to equivalent in practice. As on the S35 and S40, access on the SARL 42 would be through a side hatch located on the hull’s right side.

Turret design: The challenge of a 3-man 75 mm-armed turret on a narrow hull

The main point which would make the SARL 42 differ from previous Somua tanks, more so than the welded hull, was to be its turret and main armament. From the start, it was decided to arm the projected vehicle with a turreted 75 mm gun, which would be a considerable increase in firepower in comparison to the previous 47 mm SA 35 main gun. It would, however, also make the presence of more crewmen in the turret – preferably 3, in comparison to just one in the APX-1 CE or ARL 2C of the S35 and S40 – a necessity in order to successfully operate the larger gun.

Though it was widened in comparison to the S40, at merely 2.28 m, the SARL 42 remained a fairly narrow vehicle, and, being planned to be fairly light as well, the turret it was designed to mount ought to be relatively limited in size and in weight, despite the will to give it a three-man crew and 75 mm gun. No French tank that was produced or even reached the prototype stage prior to 1940 had had a three-man turret – even the gigantic FCM 2C of the early interwar had merely two men operating the 75 mm – but that does not mean no work had been done on the matter. In the late 1930s, French engineers had worked on three-men, 75 mm-armed turrets for various tanks of the G1 program. ARL, notably, had designed a three-man turret, the ARL 3, which appeared to be a solid candidate to be mounted on the G1R, the G1 which appeared to have been by far the favorite of the program. The G1R and SARL 42 were to be vastly different vehicles – the G1 being heavier and wider – and obviously, the ARL 3 turret was not to be straight up fitted on the new tank. However, the engineers which had worked on its design were pretty much the same team that would design the SARL 42’s turret, and as such had some previous experience working on an at least similar concept.

The result of the design team’s work was a fairly peculiar turret. The SARL 42 indeed had a three-men turret – but it used some original design elements to make it work. The turret was at its highest in the center, and at the rear – this was due to the presence of a telemeter.

Two crewmen sat to the sides of the gun – the loader to the right and the gunner to the left. Due to the turret being lower on the sides – as a way to save weight and space mostly – they were not actually positioned entirely within it, and only their busts would reach out into the turret, while their legs would be in the tank’s hull. The gunner would operate both the gunsight and telemeter, while the loader would also assume the role of radio operator, with a radio set being located in the turret. As for the commander, he sat in a form of bustle at the turret’s rear and had a commander’s cupola. At its highest, on top of this cupola, the tank was 2.84 m high – about 22 cm more than on the S35 and S40. The turret in itself was 1.125 m high. It appears that there were plans to install a machine gun mount for either one or two anti-aircraft machine guns (very likely 7.5 mm MAC 31s) on top of the turret.

The tank’s turret was planned to feature both an electric motor and be able to be hand-cranked, as most turrets of the era.

The most distinctive element of the turret was its large, 1-meter telemeter, destined for use by the gunner. The commander apparently could also operate it, as well as use internal binoculars.

The armor layout retained for the turret was 30 mm on all sides – lighter than the 40 mm of the S35 and S40. The roof would perhaps have the same thickness as the other sides, at least on parts. The inclined roof, being higher at the rear, would make it a lot more vulnerable than most other roofs found on typical armored vehicles.

The main armament of the SARL 42 was a 75 mm gun. As with many elements of the tank, it was at least partially newly designed, but based on previous work. Designing the gun was a task of a bureau of the CDM, led by artillery engineer Lafargue and located in Montauban, near Toulouse. In this case, the 75 mm of the SARL 42 was based on the 75 mm model 1933 fortification gun, itself based on the old 75 mm mle 1897. The gun mounted on the SaU 40 and ARL V39 prototypes was based on the same model 1933. However, it was far from identical to the one featured on the SARL 42. For example, the SARL 42 did not have any form of barrel shroud. In comparison to the old 75 mm mle 1897, the SARL 42’s gun had a shorter barrel. At 2.39m (L/32) long, it was 30 cm shorter. This resulted in a slight reduction of the muzzle velocity, though, at 570 m/s, this was only by a mere 15 m/s. The recoil, however, was quite moderate, which made the use of the gun in the SARL 42 a non-issue. Shells fired included the 1897/1940 obus de rupture armor-piercing capped shell (APC) and the 1915 obus explosif high-explosive (HE) shell. The exact performances of the gun do not appear to be known, they would likely have been fairly similar to, for example, the M4 Sherman’s 75 mm M3 gun. Though the quantity of 75 mm ammunition stowage on the SARL 42 is unknown. We know a small emergency rack was located on the right of the turret, while the vast majority of shells would be carried within the hull. Magazines for the tank’s coaxial MAC 31 machine gun were also located on the right of the turret. The 75 mm’s mount was protected by a rather large curved mantlet. With the 75 mm L/32 gun, but without its basket, the turret was to weigh in at 3,200 kg. The tank would, overall, be around 22 tonnes.

A more powerful gun: L/44, but not Rheinmetall

The original gun designed for the SARL 42 was an L/32 75 mm gun. After designing this gun, the CDM team, under the direction of engineer Lafargue, put themselves to work trying to design a more powerful 75 mm gun which would be mounted in the SARL 42 project, and provide better anti-armor firepower.

The resulting gun was inspired by a number of pre-war projects. Its ballistic profile was based on the Schneider 75 mm model 1932 anti-aircraft gun, which was also L/44. However, this gun would have been too large, particularly breech-wise, to mount into the turret of the SARL 42. As a way to solve this problem, inspiration was taken from fortification guns, which were designed with enclosed spaces in mind. The adaptation of the L/44 gun was based on a fortification gun design by Chantiers de la Loire. The breach construction was taken straight from the 75 mm model 1933 fortification gun, on which the L/32 gun had been partially based.

This L/44 gun fired the same ammunition as the L/32, however, it did so at a higher velocity, 715 m/s for the APC and 700 m/s for the HE shell. It is known that, fired from this gun, the 1928/1940 APC shell would penetrate 80 mm at 1,000 m. In general, in comparison to the L/32, which would be in the same ballpark as the Sherman’s M3, the L/44 would be approximately similar to the 75 mm L/43 to L/48 guns found on StuG III/IVs and Panzer IVs of the mid-to-late war.

And… where to make it?

By 1942, the team which had worked on the SARL 42 had a fairly well-established design. However, it ought to be remembered the SARL 42 was a vehicle that had been designed in secrecy – not only from Germany but also from the higher-ups of the Vichy Regime. As such, it could never be mass-produced within the unoccupied, mainland territories of Vichy, as tanks would never be discreet enough to be hidden from their own country’s government or the German armistice commission. Indeed, all covert Vichy projects which saw technical materialization – namely the Panhard 178 CDM and CDM armored car – were quite less ambitious than the SARL 42.

So, where and in which circumstances would the updated Somua design have been produced?

A number of different options existed. In circumstances such as the ones Vichy found itself in 1942, or which would happen fairly realistically, the SARL 42 would have to be manufactured abroad from mainland France. These scenarios pretty much all entailed German forces attacking the unoccupied part of Vichy France, and the SARL 42 being produced abroad in order to help equip French forces in exile or allied nations to retake the French mainland. Production in North Africa was considered. Though much less risky than in mainland France, it would require some very significant efforts to set up an industrial base sufficient to produce tanks from the ground up, and as such was not really a possible scenario.

The more likely scenario, at least in the eyes of the French engineers, appears to have been production in a friendly and more industrially-free and capable nation than the Vichy regime, constrained to its heavily monitored mainland or industrially poor colonies. In case of a German invasion of the Free Zone, this would very likely have been the United States. Though this may seem odd with today’s lens, back in June of 1940, a lot of French projects (including, within others, the Renault DAC 1 and B1 Ter) had been considered for manufacture in the USA if France was to continue the fight against Germany in exile. This did not end up materializing largely due to the armistice of 1940, though a team of French engineers led by one named “Molinié” was indeed sent to the USA and appears to have at least partially contributed to early war American tank designs. As such, the American option was not the improbable one in the eyes of Lavirotte’s engineers. They pretty obviously did not know much, if anything, on the subject of the M4 Sherman – with such a tank, more capable and with more evolutionary potential than the SARL 42, in American production, the French design likely would not have been produced for long.

Another, more realistic option, which was also considered from the start, was that the SARL 42 would be a tank design kept in order to resume tank production once France would be, in a way or another, liberated – either by Vichy opposing Germany and resisting an invasion, or France being liberated by the Western Allies after the German occupation. In this case, it would have been a ready, ‘off-the-shelf’ design, with which the French tank industry could resume operation without having to design a new vehicle from the start. Though those circumstances ended up happening, the SARL 42 did not end up entering production or even prototype stage, for a number of reasons – among others, technical obsolescence by 1944 but also, perhaps, unknown whereabouts of the plans.

What role for the reborn Somua?

Realistically, even if conditions did align for the production of the SARL 42 to be able to start, the tank could not enter service before 1943 or 1944. By such a point in the war, its performances would have been a mixed bag.

Based on the 1930s S35, a fairly narrow and light cavalry tank design, the SARL 42 could never hope to compete with the heavier and wider Panzer IV, nor the newer T-34 and M4 Sherman, in terms of evolutionary potential. This is easily seen when looking at the vehicle’s armor layout. With 40 mm on the hull front and 30 mm on the turret or hull sides, the SARL 42 would have been very lightly armored, unable to resist any modern anti-tank weapon by mid-war, even less late-war.

The tank’s firepower is more complex though. With the L/32 gun, similar to the M4, the SARL 42 would definitely have been quite a poor design – armed with a gun able pretty much capable only of infantry support and anti-tank duty against light or moderately-armored medium targets, it would be outdated in pretty much all regards. With the L/44 though, the vehicle may have had some limited potential. Though the SARL 42 had a high silhouette, its high observation cupola and telemeter would likely have allowed some good observation capacity while only keeping the cupola and telemeter – about 55 cm high, and fairly narrow – peeking. If a good target was found, the tank could then reach out a little more in order to put the gun on target. With the L/44, though the SARL 42 would be unable to deal with newer German designs such as the Panther, Tiger I, Jagdpanzer 38(t), Jagdpanzer IV or Jagdpanther frontally, it would be able to deal at least decently with most other targets – and most vehicles in this list could at least in some way be engaged from the side. While it could never hope to be a decent, modern frontline medium tank that could compare to a Sherman or Cromwell, the SARL 42 may have found some use in a role more akin to a tank destroyer – albeit a turreted, covered one – than a medium or cavalry tank.

Premature end by the hands of Case Anton

As with pretty much all other undercover armored vehicle design projects undertaken by the CDM in the Vichy Regime, the SARL 42 would come to a swift end due to the German invasion of the unoccupied, ‘free’ zone of Vichy France, on 11th November 1942. The plans of the project were not destroyed but instead hidden inside a mechanical workshop in Dijon, Burgundy. They would survive the war. Despite what one may expect, the SARL 42 did not end up being entirely irrelevant to the French tank industry post-war, far from it.

The SARL 42’s legacy: Off-the-shelf tank gun designs

By the liberation of France in the summer of 1944, the SARL 42 had now become a vastly obsolete design. Even if high efforts were put into restoring the French tank industry, months would be needed before a prototype would leave a factory, let alone a production run. By that time, with the French Army equipped with the superior M4 Sherman in considerable numbers, the need for the SARL 42 was long gone.

However, some considerable work had been done into designing two guns – The L/32 and L/44 – for the SARL 42. Those two would not go to waste but instead be featured on a number of postwar projects.

The L/32 gun was redesignated as SA 45, and featured on a project for a new production run of the Panhard 178 armored car, which would mount this 75 mm gun in a cylindrical turret. In the end, though the cylindrical turret was adopted, no efforts were apparently undertaken to produce the SA 45, and the design ended up going into production with the pre-war 47 mm SA 35 gun – originally found, notably, in the Somua S35. The SA 45 may, or may not, have been manufactured at least once. It was possibly mounted in the Voisin CA 11 colonial amphibious tank prototype, though this is only guesswork, as this prototype’s gun, though known to be a 75 mm short gun, has never been fully identified.

As for the L/44, it would make its way onto the first produced ARL-44, within a cast turret designated as the “ACL-1”. Though it is often claimed this turret mounted the American 76 mm M1, this was not the case. It is indeed the 75 mm initially designed to upgrade the SARL 42’s firepower which would make its way into France’s first new tank design post-WW2, though it would swiftly be replaced by a more modern 90 mm gun. Like the SARL 42’s L/44, this 90 mm SA 45 gun would be based on a prewar anti-aircraft piece.

Conclusion – The secret Somua, condemned to obscurity

The SARL 42 is one of several undercover armored vehicle production projects undertaken by the CDM in Vichy France, alongside the CDM armored car and Panhard 178 CDM – all very peculiar and fascinating works studied, and for these latter two produced, in exceptional conditions and very tight secrecy.

The SARL 42 was the project which was the closest to a capable, modern tank – but it would also have been the hardest and most expensive to manufacture in secret, a prospect which could never have been seriously considered. Unlike those other CDM projects, it does not appear to even have been close to prototype manufacturing, remaining on the drawing board for its entire history, though some considerable design work was performed, notably when it comes to the vehicle’s guns.

This work definitely did not go to waste – the SARL 42’s guns would play a non-negligible role in kickstarting the French tank design and industry services back up at the end of the war, and many of the engineers who worked on projects such as the ARL 44, including notably Lavirotte, were veterans from the secret SARL 42. As such, it played a significant role in keeping whatever was left of a French tank industry alive, albeit on life-support, while the country was divided in two and under tight occupation. In a somewhat tragic irony, this was not too different from the covert projects undertaken in Weimar Germany, which were also in violation of the peace treaty or armistice of the time, and in which production was mainly considered outside of the designing country. Those projects also at least kept the industry and designers active and trained.

 

SARL 42 specifications
Dimensions (L-H-W)	5.42×2.84×2.28 m
Crew	4 (Driver, Loader/Radio, Gunner, Commander)
Propulsion	8-cylinders, 13,745 cm3 petrol, producing 230 hp at 2,200 rpm/220 hp at 2,000 rpm
Suspension	Leaf springs bogies
Weight	~22 tons
Power-to-weight ratio in hp/tonnes	~10.4
Armament	75 mm L/32 (570 m/s) or L/44 (715 m/s) gun coaxial MAC 31 7.5 mm machine-gun Optionally 1 or perhaps 2 turret-mounted anti-aircraft machine-guns (likely MAC 31s)
Armor layout	40 mm (front hull) 30 mm (Turret, rear) 20 mm (hull sides)
No. Built	0

Sources

GBM 88, July-August-September 2009, “Le Somua S40”, François Vauvillier, pp 62-69
GBM 89, October-November-December 2009, “Les Somua de l’ombre (I)”, Stéphane Ferrard, pp 44-49
GBM 90, January-February-March 2010, “Les Somua de l’ombre (II)”, Stéphane Ferrard, pp 54-59
Char-français
French military archives at Châtellerault: Note pour la direction du matériel, N°28.750, 8 Juin 1945