Sunday, 24 December 2017

The Best French Pre-War Tank

France entered WWII with a rather controversial set of tanks. While most nations began to produce medium tanks, the French army was in a catastrophic position with medium tanks. The prioritization of light Renault R 35 and "battle" (in practice, heavy) Char B1 bis tanks resulted in only 50 medium tanks available for infantry.

Unexpectedly, France built a large number of medium tanks, but for cavalry, and they were officially referred to as armoured cars. These were SOMUA S 35, tanks whose combined characteristics made them the best tanks the French had before the war.

Thick-skinned cavalry

Strong positions of cavalry in the French army led to a situation similar to what took place in the USA and Japan in the early 1930s. Officially, cavalry had no tanks in these countries, since tanks were traditionally used for infantry support. In practice, there was a new type of vehicle, referred to as "combat car" or "armoured car". In reality, these were tanks, sometimes medium tanks, but more often light tanks crewed by 2-4 men and armed with machineguns. The most important requirement for these vehicles was high mobility.

SOMUA AC 1, 1932. At first, an armoured car was actually a candidate for the armoured car tender.

At first, French cavalry tanks were headed in that same direction. The first armoured vehicle the French cavalry had was the AMR 33 (Automitrailleuse de reconnaissance, reconnaissance armoured car). The improved AMR 35 appeared later. These two-man vehicles armed with machineguns fit into the classical cavalry tank niche. In parallel with the AMR program, a program for a more powerful vehicle was launched: AMC (Automitrailleuse de combat, combat armoured car). The first member of this family was the Schneider P16, which had a more serious armament: a 37 mm SA 18 cannon and a coaxial machinegun.

The situation began to change in 1933. This development was influenced by Hotchkiss, who proposed the concept of a light tank with cast armour. On August 2nd, requirements for a new vehicle were composed, and 14 companies placed a bid for the tender. Hotchkiss itself quickly declined to participate. It's possible that the company evaluated its chances at a victory and decided to seek another customer: the cavalry. The result was a tank that was very similar to the Renault R 35, but 1.5 times faster, indexed Hotchkiss H 35. The project "consumed" the AMR 35, taking its place.

SOMUA AC 3 "armoured car". October 1934.

The Schneider-Creusot conglomerate also participated in the light tank tender. Unfortunately, no data regarding the vehicle survived, other than the fact that it had a crew of two. The development was done by its subsidiary, Société d'outillage mécanique et d'usinage d'artillerie (SOMUA). Starting with the Schneider CA1, the first mass produced French tank, it was SOMUA who worked on the conglomerate's armour development. This was true for work on the Char B project and cavalry tanks as well.

Long before the tender for a 6 ton light tank, the company was working on the SOMUA AC 1 armoured halftrack for the AMC project. Unlike the Schneider P16, the three-man vehicle had a layout that was much more similar to a tank. A heavier armoured car, the SOMUA AC 2, was designed. Meanwhile, the cavalry brass knew that what they really needed was a tank.

A distinguishing feature of the model is its large muffler. The real vehicle had a much smaller one.

A meeting was held between SOMUA representatives and cavalry command. In it, a concept of a new tank was born, which combined technical solutions from the light armoured car designed for the 1933 tender and the AMC requirements. The mass of this three-man tank would be about 13 tons, top speed would be no less than 30 kph, its armour would be 30 mm thick, and its cruising range should be 200 km.

In May, the armour was thickened to 40 mm, which would reliably protect it from the 25 mm gun. A 47 mm gun with a coaxial machinegun was proposed for armament. The result was not an armoured car, but a tank similar to the Renault D2, except faster. The program was finally approved on June 26th, 1934, by General Flavigny, the commander of French cavalry.

The 190 hp engine that was designed by  Janvier, Sabin et Cie.

The development of this vehicle, indexed SOMUA AC 3, was a serious challenge for the company. A number of major issues had to be worked out quickly. The question of an engine was especially serious. SOMUA built trucks, but their engines were ill-suited for the new tank. A more powerful engine was needed, and fast. SOMUA turned to the Janvier, Sabin et Cie company, which worked on engine design. They quickly developed an 8 cylinder V-shaped engine. The full set of blueprints was purchased, which SOMUA used to design its own engine, which had some design similarities with the Hispano-Suiza 8B. At 12.7 L, it put out 190 hp.

The design of the suspension was similar to the one developed by Škoda.

The suspension was equally important. SOMUA had no suitable solution, and one had to be designed from scratch. A Czechoslovakian connection can be traced here. Indeed, there were friendly relations between Schneider-Creusot and Škoda, which helped SOMUA out with its task. The Škoda S-II-a, aka LT vz. 35, is often indicated as the source of the suspension. This is a dubious claim, as the development of this tank began around the same time as the AC 3. For some reason, some historians forget that a similar suspension was used on the earlier S-II tank, aka Skoda SU. The suspension that SOMUA designed was a little different, but its Czechoslovakian roots are clear.

Automitrailleuse de combat AC 3 on trials, spring of 1935. The turret is substituted with a dummy.

A draft project of the AC 3 and a wooden scale model were ready by October of 1935. Meanwhile, Renault was not sitting still, as they also wished to get an impressive contract for 600 AMC vehicles. The company quickly designed a project called AMC 40 mm. There is no precise information about this vehicle, but, most likely, this was a further development of the Renault YR cavalry tank, also known as the AMC 34. The cavalry rejected it, without even spending money on a prototype. The AC 3's fate was different. An order was given on October 12th, 1943, to produce a prototype of the vehicle. 

From the front, the AC 3 was very distinct from the production tank.

Work on the SOMUA AC 3 began in November of 1934, and on April 11th, 1935, the vehicle with registration number 745-W1 was ready. Considering that many components had to be designed from scratch, this development is very short. Significant changes were made to the initial requirements during development. It was impossible to stay under 13 tons with the required amount of armour, so the weight limit was increased to 17 tons. Since there was no turret at the time of assembly, it was replaced with a dummy. The cavalry tank went through trials from July 4th to August 2nd, 1935, equipped like this.

AC 3 after conversion, March 1936. It received an APX 1 turret and a 47 mm SA 34 gun.

The result was typical for French pre-war tank development. Hotchkiss' idea of assembling a hull from large cast components was used as much as possible. The hull consisted of only four castings: two halves of the lower hull, the turret platform, and the cover of the engine compartment. The parts were bolted together. Great precision was required to built these components, but they were easy to put together.

The configuration of the AC 3 hull was far from what production tanks ended up with. There were very major mistakes, the most visible of which were headlights placed on the front of the hull. They were massive, and were attached by bolts, which made the whole design very vulnerable. However, it's a prototype's job to reveal design flaws during testing so that they could be corrected.

The same tank after installation of the SA 35 cannon. It is often said that this is a tank from the pilot batch, but photos taken from other angles show that this is the same 745-W1 vehicle.

The characteristics of the SOMUA AC 3 was one of the best medium tanks of the time. Equipped with thick armour, which could reliably protect from the 3.7 cm Pak at over 300 meters, this tank also had what the Renault D2 lacked: mobility. The results surpassed the cavalry's expectations. The top speed of their "armoured car" was 10 kph higher than required, and the off-road mobility was still decent. The suspension allowed for smooth driving, and visibility from the tank was good, despite the need to rework the observation devices.

The tank was sent to the factory after its trials, where improvements were applied until March of 1936. A decision to put the AC 3 into production was already made in late November of 1935. It was accepted into service on March 25th, 1936, under the name Automitrailleuse de Combat modèle 1935 S. It was sometimes known as the Char 1935 S, but it is most famously known as the SOMUA S 35.

Medium masterpiece

Contract #60 178 D/P for 50 tanks was signed on March 25th, 1936, but the deal was as good as done by November 21st, 1935. Initially, the cavalry had grandiose plans for the SOMUA AC 3, planning on ordering 600 tanks of this type, enough to equip three light mechanized divisions ((Division Légère Mécanique, DLM). The plans were quickly corrected, as SOMUA's capabilities were limited. Hotchkiss managed to find a loophole for its light tank. The order was split in half: 300 SOMUA S 35 tanks and 300 Hotchkiss H 35 tanks.

According to the TO&E of a DLM, it had to include 96 SOMUA S 35 tanks. Of those, 84 formed 8 squadrons, 4 more were used as commander's tanks, and 8 were kept in reserve.

SOMUA AC 4 without a turret platform or an engine compartment roof.

The prototype returned to trials in March of 1936. In addition to correcting design flaws uncovered during testing, the tank was finally given a turret. There was not much to choose from, and the APX 1 turret armed with a 47 mm SA 34 gun was used, just like on the Renault D2.

However, the tank did not stay like this for long. It was obvious that the SA 34 was too weak to combat tanks with 60 mm of armour. This was the level of protection of the Char B1 bis. For this reason, the turret soon gained a more powerful weapon: the SA 35, whose shell could penetrate 60 mm of armour from a kilometer away. Nevertheless, the first 4 production SOMUA S 35 tanks received APX 1 turret with SA 34 guns, which were later replaced with APX 1 CE turrets and SA 35 guns. These tanks were built in January of 1936 and were sent to the 4th Tank (Cuirassier) Regiment for trials.

SOMUA S 35, registration number 67225, the third production tank. Additional fuel tanks are shown.

The result of trials and improvements was the modernized AC 3, which was called AC 4 at the factory. This vehicle was the prototype of the production SOMUA S 35. This first large batch was laid down in July of 1936, but the vehicles were not ready until January of 1937. The bottleneck was the capabilities of APX. It took half a year to obtain the turrets. In the meantime, one important change was made. The APX 1 turret ring was 1022 mm in diameter, which was not enough to properly use a 47 mm gun. An improved turret called APX 1 CE (chemin élargi, enlarged path) had an 1130 mm turret ring. The extra 11 centimeters were sorely needed.

The guns also took their sweet time. Production of the SA 35 only began in January of 1937.

The same tank from the left side. A cast serial number on the turret platform reveals that this is tank #3.

There were plenty of changes in the design of the chassis. The mass of the tank grew to 19.5 tons after all the changes, but the mobility of the tank remained almost the same as on the AC 3. The front of the hull was redesigned. The designers removed the headlight casings, and their design was simplified.

The observation devices were improved. The driver's station was moved forward, which improved his vision. The front observation device could be raised, which improved visibility on the march. The observation devices on the turret were also changed. It was still called APX 1 CE, even though it was almost identical to the APX 4.

The rear of the hull was also altered. The air intakes from the sides of the engine compartment were removed, as they were considered weak points. The track link design was altered. Another improvement was the introduction of external fuel tanks. They were attached along the right side, and their clips allowed them to be easily removed.

This tank has no observation devices. Due to a supply issue, some tanks were sent into service without them.

The contract for the first 50 tanks was finished in the second quarter of 1937. Tanks built according to this contract received serial numbers from 67 225 to 67 274. All vehicles were sent to 1 DLM. Meanwhile, SOMUA signed another contract in 1936, #61 361 D/P, for 50 more tanks. For a number of reasons, largely connected to subcontractor delays, delivery of this batch was late. Only 17 tanks were delivered by January 15th, 1938, and all 50 were done by April 15th. The tanks were shipped without observation devices, among other items.

The SOMUA S 35 was first shown to the public during the Bastille Day parade on July 14th, 1938. Tanks of the second production batch, assigned to 2nd DLM, marched in the parade. Even these tanks lacked observation devices in the hull. This was just the tip of the iceberg. Due to delays on behalf of APX, the tank production wing of which was nationalized and renamed to ARL, not all SOMUA S 35 tanks had turrets by the summer of 1938.

Tanks from the second batch received serial numbers 22 232 to 22 381.

Tank with registration number 67237. Chains were a popular towing method at the time.

Issues with subcontractors impacted the third batch as well, produced under contract #70 919 D/P, signed in 1937. Unlike the first two contracts, the third ordered 100 tanks. These tanks had registration numbers 819-918 and were used to bring 1st and 2nd DLM to full strength. 28 tanks were built by July 15th, 1938, but only 96 of the 128 delivered SOMUA S 35 tanks had turrets. Delivery of the third batch was completed in March of 1939.

It might look like the tank was being built slowly, but 200 tanks in 2.5 years is quite a lot for French peacetime industry. To compare, the first order for Char B1 bis tanks was made on October 8th, 1936, and only 90 of these tanks were built by March of 1939 by three companies.

The first public demonstration of the SOMUA S 35, Paris, July 14th, 1938. The tanks still don't have observation devices.

The first three contracts made it possible to fully equip two light mechanized divisions. Production did not end here. The order was increased to 500 tanks. Contract #80 353 D/P for 125 tanks was signed in 1938. These tanks would be used to equip the 3rd DML, which was not yet formed. 61 tanks were delivered by September 1st, 1939, and 9 more were in progress. The rate of production increased after the start of WWII. SOMUA delivered 11 tanks in September, but 13 tanks every month after that. Thanks to that, all tanks ordered by contract #80 353 D/P left the factory within the first 10 days of January 1940. These tanks had serial numbers from 10 634 to 10 758.

Tanks being assembled at the SOMUA factory, November of 1939. Casting large parts simplified assembly. As a result, the SOMUA could be produced quickly.

Production plane for the SOMUA S 35 were revised towards the end of September of 1939. The total volume of production was reduced to 450 units, and the improved SOMUA S 40 would be produced after that. The last contract for SOMUA S 35 tanks was #88 216 D/P, signed back in 1938, which called for 125 tanks. Assembly began in January of 1940, and 16 tanks were built within that month. Production increased again in March of 1940, and 22 tanks were delivered every month starting in May. Serial numbers from 50 210 to 50 334 were reserved for this contract. In reality, fewer tanks were produced than that. SOMUA factories were captured by the advancing Germans in June. Between 427 and 440 tanks were built until then, depending on the source.

Ointment in the fly

Like other French tanks, the SOMUA S 35 had built-in drawbacks. The biggest one was its one-man turret. The progressive design and impressive characteristics had a similarly impressive price tag. One SOMUA S 35 cost 982,000 francs, the same as nearly five Renault R 35 tanks.

However, as far as effectiveness goes, this "armoured car" had no equal. Unlike the slow infantry tanks, the SOMUA S 35 had impressive mobility. Its average speed of 30 kph was higher than the maximum speed of the infantry tanks. The cavalry tanks were also very reliable.

A sad outcome of the May-June campaign. The halftrack on the photograph is the SOMUA MCG, a close relative of the AC 1.

Even 400 quality tanks could not solve the French army's problems. It's also important to add that only the 1st and 2nd DLM were properly trained on these tanks. The rapidly formed 3rd DLM was not prepared as well, as de Gaulle wrote in his memoirs. Attempts to plug rapidly multiplying holes in the French defenses with cavalry tanks failed. The SOMUA S 35 was a drop of ointment in a massive fly. 

Nevertheless, one can confidently say that French cavalry commanders had greater foresight than their infantry counterparts. The SOMUA S 35 was one of the best tanks of the early war. These tanks fought for a long time, although no longer under the French flag. That is a topic for another article.


  1. This comment has been removed by the author.

    1. (Some typos)

      I thought that the AMC 35 was the best french pre-WWII tank. It has the same gun as the S35 and has a 2-man turret. The only one of the war that the french used if I am not mistaken… The armour is less then on the S35, more like 25mm on the hull and 30-35?mm on the turret.

      Still, I think the S35 if one of the most stylish tanks of the war and this was a great read, so no criticism intended! :-)