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WW2 French Prototypes

Char de Forteresse ARL

France  (1939)
Super heavy tank – Blueprint only

In 1937, the French military requested the design of heavy breakthrough tanks to be able to take on the German Westwall Line being built alongside the French border, vis-à-vis the Maginot Line. This was the Char Lourd (Eng: Heavy tank) program. Three companies presented designs, ARL, AMX and FCM, but the program was halted, as the tanks would have been too expensive, and too few could have been built to have any significant impact on the battlefield.

So, naturally, the weight limits were lifted, allowing the companies to create even heavier and more expensive designs.

History

The authorities were most impressed by the design of the FCM F4, granting, in February 1938, some changes in the requirements: A 75 mm gun in the turret and no weight limits. As a result, the French Supreme Command granted FCM, on 6th April 1938, a contract for the development of such a super-heavy tank; the Char F.

Simultaneously, a commission headed by Julien François René Martin reanalyzed the threat presented by the Westwall, urging the revival of the Char Lourd program. These new versions would be differentiated by being called Char d’Attaque des Fortifications (Eng: Fortification Assault tank). The new design should have had a gun in the turret, suitable for close-range fire, and be immune to the best anti-tank guns in Germany at the time. Hence, speed was not of importance, with a 10 km/h top speed seen as satisfactory. In addition, it was to have outstanding trench, ditch, and river crossing capabilities, leading to a very long vehicle. In April 1938, the High Command approved the plans and dispatched another commission, with the task of fine-tuning the requirements and figuring out if the 45 tonne Char Lourd program could have been revived instead of making new, heavier designs.

Second Commission’s first meeting

On 4th May 1938, the Direction des Fabrications d’Armement (Eng: Armament Production Department) wanted to call this new program the Char H, but it was rejected, so as to not bring confusion with the Hotchkiss H35 tank. Five days later, the second commission, at its first meeting, wanted to make two types of tank, a 45-tonne tank and a superheavy tank. French author Pierre Touzin states in his book, ‘Les véhicules blindés français, 1900-1944’, that the commission wanted the tanks to be immune to at least 47 mm guns, so they agreed on 120 mm armor thickness. They would also give the option of 75 or 47 mm guns (or a combination of both) in a turret or more. The 75 mm would only be required to have a muzzle velocity of 640 m/s. The secondary armament had to include a flamethrower. However, the Commission did acknowledge the dangers and space taken by the flammable fluid, but they also had suspicions about the effectiveness of mounting such a weapon. Thus, they proposed either:

  • A towed trailer carrying the liquid fuel
  • A very bulky and heavy tank

Nonetheless, the problems of transporting such a vehicle by rail were solved by simply deciding to avoid rails and to carry it on roads.

45 tonne/articulated option

The first solutions came regarding the 45-tonne vehicles. It was to be armed with a cannon, a flamethrower, and machine guns. It was to be able to reach a top speed of 10 km/h. A prototype study was made, of slightly smaller dimensions, similar to that of the Char G1, with 100 mm of armor and a gun inside a casemate.

Mockup of one of the Char G1 from Renault. Despite sharing nothing in common to the Char de Forteresse program, the first prototype study was around the same size as the G1.
Source: Globalsecurity.org

The Commission did confirm that the 45 tonne Char Lourd program was not enough, as it was impossible to have 120 mm of armor, a 75 mm gun, and good trench crossing capabilities under 45 tonnes. After all, all Char Lourd designs exceeded that mark and had even thinner armor (100 mm). Therefore, to be able to fulfill the requirements, the creation of an articulated, modular design was brought up. It would be brought on roads via trucks and be reassembled before reaching the frontline.

Installment of a flamethrower could not be done either, as it would have required a special towed trailer, also with 120 mm thick armor. It was calculated that the fuel volume required was 6 m3 for just 4 minutes of firing. The concluding idea was that there should be a gun tank and a flamethrower tank, built jointly, in two parts.

Superheavy option

The second idea was the creation of a super-heavy tank. It was to also have a modular construction, but only with the weapons, main cannon, flamethrower, and machine guns, which could be demounted for easier transport. This was all the idea of the Infantry Directorate, which itself resumed General Estienne’s previous plans. However, the main problems with this variant were that:

  • The assembly would require a lot of resources
  • The turret would be overcrowded by the main gun and flamethrower

They did acknowledge that a tank with crossing abilities similar to that of the Char 2C (4.5 meters) and a fording depth of 1.4 meters but also with 120 mm armor would have weighed between 150 and 200 tonnes, a benchmark where even a modular vehicle would not be effective.

LEGO tank option

A third idea was brought up at the meeting. To be able to enjoy the advantages of a super-heavy tank but to also have the same transportability as a heavy tank, they came up with a 60 to 65-tonne tank that would be made entirely out of portable modules: turrets, ammunition, fuel, engine, etcetera. This would leave an empty hull of around 45 tonnes, which could be transported by trucks. Of course, the main downside was that the tanks had to be reassembled bit by bit before being combat-ready.

Second meeting

On 22nd July 1938, the new commission had its second meeting. Tests were made to see if 100 mm was in fact, sufficient protection. It was deemed enough to withstand fire from existing 75 mm guns then in service, but would not be enough for newer 75 mm guns firing AP, thus the 120 mm armor was necessary. The existence of the German 8.8 cm Flak gun was also seen as a reason to keep the original 120 mm threshold.

The results of the experiments surrounding the flamethrower and its dilemmas were to come in by the end of the summer.

Further rework on the designs allowed for ditch crossings of 6.5 to 7 meters. It was also remarked that trucks could only carry a weight of 35 tonnes, with an 8 axle transport trailer. However, railway wagons could transport a weight of 100 tonnes and special axles could be built if necessary, reviving the option for rail transport.

Several design options were evaluated at this meeting as well.

Char Minimum: armored with 120 mm thick armor, a 75 mm gun in a turret, and two flamethrowers (probably in the hull). The cannon version weighed 56 tonnes and could be reduced to 40 tonnes for transport. The flamethrower variant was a bit heavier, at 57 tonnes, plus a towed trailer. The Char Minimum’s poor trench crossing distance of “just” 2.5 meters lead to it being rejected.

Char Maximum: Classical layout tank with 120 mm armor, 75 mm gun in a turret, and just one flamethrower. It could cross 3.6-meter trenches (still less than the Char 2C). Although it weighed around 89 tonnes, it could be demounted into two main pieces for transport.

Train Boirault: French engineer Monsieur Louis Boirault was, and still is, known for his unorthodox solutions regarding tank design, especially trench crossing. As early as 1915, he presented articulated tank trains that would, theoretically, improve cross country capabilities. This 1938 variant had three self-coupling main parts and weighed 125 tonnes in total (41.6 tonnes each). However, its turning radius was large and the couplings unreliable and hazardous. Reducing the train to just two modules fixed some issues but created others, and was ultimately rejected.

One of Boirault’s later inventions. This one uses several S35 like tanks plus a middle section.
The 1938 125 tonne version might have been something similar, just larger.
Source: Andrew Hills

Char Squelette: Inspired by the WWI ideas of the Skeleton tank and Boirault Machine, this variant greatly interested the Commission, both out of curiosity and also actual implementation. It had a small armored ‘box’ that was attached to rotatable beams, shifting the vehicles’ center of gravity, thus allowing it to cross 8 meter long trenches. Unsatisfactorily, the turret was unable to rotate a full 360° and many of the automotive elements and beams were exposed to potential enemy fire. The total weight was 110 tonnes.

The American Skeleton tank. The French version would have been rather similar, but much larger.
Source: Landships.info

The commission approved the Char Maximum and Char Squelette and insisted upon the 120 mm armor, 75 mm gun in the turret, and one flamethrower.

In September, the Supreme Command asked for the immediate design of a Char Maximum and a replacement solution for the Char Squelette.

L’Atelier de Construction Rueil (ARL), located on the outskirts of Paris, was tasked with the development and creation of blueprints. They had previous experience with heavy tanks, as they had presented three designs a year earlier for the Char Lour program. FCM, Somua and AMX, the other main French tank factories, were all busy with other programs. Besides the aforementioned characteristics of the Char Maximum, they were to also protect the bogies and wheels with side skirts, and the tank had to be demountable into 45-tonne sections.

In the summer of 1939, ARL presented the drawings of two different alternatives: an articulated and a classical long variant. Besides the layouts, they were more or less identical. They called it Char de Forteresse (literally Fortress tank).

Two drawings

The articulated variant had two 60 tonne modules, for a total weight of 120 tonnes. One was the fighting compartment, with the weapons and crew, and the other was the engine and fuel compartment. Each module had its own driven sprocket, indicating that the coupling between the two was more complex, as power would also have to be transferred between the two. It is unspecified if the vehicle turned by pivoting the modules, like a BV206, or by breaking the tracks. Considering this was never specified, it is unlikely to have included such a steering system, as it also added additional mechanical complications. The Commission noted that there were not any visible problems with the design, however, they did express a desire for a second gun in the “rear”. It is unclear if this would have been on the rear of the armament module or the engine module. They also wanted to test and check the effectiveness of the 75 mm gun against reinforced concrete armor, the type used in the bunkers on the Westwall. The flamethrower(s?) was to also be removed since it was seen as useless against fortifications. ARL added twin engines to the designs, but the Commission only wanted one. This would free up space for ammunition, better communication between the compartments, close-range defense, and providing the crew with sufficient space.

Plans of the articulated variant. Note the lack of design on the articulation, showing just how little the design had come.
Source: Chars Français

The other drawing was a much more classical layout for a tank of this type, with a very long hull, the engine in the rear, and the turret at the front. The turret used on both designs was somewhat hexagonal in shape, with a large extension behind the gun in order to provide a better view for the commander. It is possible that it might have mounted a rangefinder as well. The running gear was long, protected by heavy side skirts. Large idlers and sprockets ensured improved ditch and trench crossing.

The second design proposed by ARL. It was extremely long, around 12 meters, for excellent trench and ditch crossing.
Source: Chars Français

Layout and components

Very few technical details are available, and it is quite likely the designs never even got that far. The main armament was an unspecified 75 mm gun, but considering previous designs, it was most likely a 75 mm Mle. 1929. It also received additional armor around the gun, characterized by the mushroom-like object on the barrel. The hull length was around 12.05 meters, the width of around 3.20 meters, and the hull height of 2.125 meters. The total height would have been 3.65 meters.

The engine and powertrain are hard to determine. Later vehicles, such as the FCM F1 and ARL Tracteur C, used two Renault 550 hp engines, but since only one engine was desired, it is hard to say what contemporary French engines could propel this 120-tonne beast. On the other hand, a 10 km/h top speed was deemed sufficient, although some sources claim it would have reached 18 km/h. This engine would have probably been attached to an electrical generator that powered the drive sprockets. The crew number and positions are also a mystery. The most likely number would be around 5 crewmen, a commander, gunner, loader, driver, and radio operator or mechanic (the radio might have been handled by the commander).

The armor was 120 mm thick almost all around. It was common for French tanks to have the same thickness all around, with small exceptions, like the top and belly armor. This shows how the tank could easily reach the 120-tonne mark, despite the small turret and even smaller armament.

Armament

The main armament was most likely an APX 75 mm Mle. 1929. This gun was originally developed for the Maginot Line and was an improvement of the gun mounted on the Char B1. ARL had previously used it on their ARL 37 heavy tank and ARL V.39 tank destroyer. The Mle. 1929 normally had an armored sleeve, but ARL gave it a ‘head’ to deflect incoming rounds.

It is unclear which flamethrowers would have been used, and they were eventually to be removed from the tank, as they were deemed unnecessary.

The 3 machine guns would most likely have been MAC-31s. Also built for the Maginot Line, these heavy machine guns fired 7.5 mm cartridges from 150-round magazines, ideal for use in tight spaces like tanks. One was in the gun mantlet, one in the hull, near the driver and one mounted on the rear, for defense against flanking infantry.

MAC-31 machine gun with a drum magazine
Source: Wikipedia

Turret

The turret was a Tourelle ARL 4 with a hexagonal shape, made out of welded 120 mm thick plates. This was rather unusual, as most French turrets were cast. The commander had a large protrusion, providing an excellent view over the battlefield. He sat on the left side of the gun and had around 7 cutouts or slits for vision, a rather archaic solution, instead of using periscopes. It was hinged on the front side of the turret, allowing the commander to enter and exit, while also providing protection. The turret was large enough to fit 3 men, the commander, gunner, who sat below and in front of him, on the left side of the gun, and the loader, who was also responsible for the coaxial (or possibly independent) machine gun in the mantlet.

German threat and merging with FCM program

Since the final design by ARL was very similar to the one FCM was working on, the Char F, the Commission decided to end the development of the Char de Forteresse in order to allow both FCM and ARL to work on the same program and speed up the development of the Char Maximum. Things took a different turn in September of the same year, as Germany invaded Poland. The High Command was not too fond of the practicality and use of these super-heavy tanks, but the Commission proceeded regardless. In a meeting held in the same month, the Commission made changes to the FCM requirements, uparmoring it to 120 mm and requesting the mounting of a 105 mm gun in the hull. The Char Squelette was finally abandoned since it was too complex.

In October 1939, AMX would also join the program, and they would all work on different designs, getting heavier and with more and more guns. ARL cast aside their original plans of the Char de Forteresse, moving on towards other plans to keep up with the new demands. They did however use the general layout for further designs. Final outcomes were the mock-ups of the ARL Tracteur C or FCM F1, all of which were terminated prematurely due to the German invasion of France in the summer of 1940.

ARL Tracteur C uncompleted mock-up, with a German soldier posing next to it.
Source: Chars Francais

Conclusion

ARL’s Char de Forteresse was an insignificant and short-lived design, but, when put together with the previous Char Lourd program and future Char Maximum developments, it highlights the cluelessness of the French military, wasting valuable time and resources on trying to counter a mainly nonexistent defensive line. By the start of the Second World War, the Westwall was not more than just a series of ditches and dragon’s teeth.

Post Scriptum – Char de Forteresse 1940

The name Char de Forteresse does show up later on, unrelated to ARL plans. On 28th February 1940, a new commission, the Commission d’Études des Chars (Eng: Tank Study Commission), set off to create the structure for future tank development and production doctrine. Similarly to General Estienne’s interbelic doctrine, there were to be three tank types:

Char d’Accompagnement: a light infantry support tank, equipped with a 37 mm SA 38 gun, 40 mm armor, and a total weight between 10 and 12 tonnes. Later models would have the 47 mm SA 35, 60 mm of armor, and a weight between 15 to 20 tonnes. Top speed of 20 to 35 km/h. This was something similar to the Somua S35.

Char de Bataille: a battle tank armed with a 75 mm and 47 mm gun and 60 to 80 mm of armor. Similar to the Char B1 and B1 bis.

Char de Forteresse: a fortress tank armed with a 75 mm, 90 mm, 135, and/or 155 mm gun. Weight of 80 to 100 tonnes and a top speed of 20 km/h.

Clearly, the French did not learn much from either the FCM 2C or any of the other designs. This second Char de Forteresse was canceled not because they were utterly pointless and unusable, but because there were not any 135 and 155 mm guns suitable for the tank.

First Char de Forteresse ARL design, consisting of two articulated sections. Illustration by Pavel Alexe, funded through our Patreon Campaign.
Second Char de Forteresse ARL design, with a more traditional, ‘battleship’ hull. Illustration by Pavel Alexe, funded through our Patreon Campaign.

Sources:

https://www.chars-francais.net/2015/index.php/7-archives/de-1930-1940/2428-1939-char-forteresse-arl
Les Vehicules Blindes Francais 1900-1944 – Pierre Touzin, 1979
Chars De France – Jean-Gabriel Jeudy

Char de Forteresse ARL specifications

Dimensions (L-W-H) 12.05 x 3.20 x 3.65 m
Total Weight, Battle Ready 120 tonnes
Crew 5 men (Commander, gunner, loader, driver, radio operator or mechanic)
Propulsion unkown, included electrical generators
Speed 10 – 18 km/h
Armament 1x 75 mm APX Mle. 1929,
3x MAC 31 machine guns
2x/1x flamethrower (later removed)
Armor 120 mm all around

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