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Somua S-35
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The SOMUA S35 was a French cavalry tank of the Second World War. Built from 1936 until 1940 in a number of 430 to equip the armoured divisions of the Cavalry, it was for its time an agile medium tank, superior in armour and armament to its competitors. It was constructed from well-sloped cast armour sections, that however made it expensive to produce and difficult to maintain. After the defeat of France, captured S 35s were used during the war by the Axis powers.
DevelopmentThe design of the S 35 comes from the changed specifications of 26 June 1934 for an Automitrailleuse de Combat (AMC) issued for cavalry use. These called for a much heavier design than had been originally specified in 1931. The new type had to be immune to antitank guns. On 17 May the Army had already contacted a subsidiary of the Schneider company — the Société d'Outillage Mécanique et d'Usinage d'Artillerie (or SOMUA) based at Saint-Ouen — to build a prototype. The company accepted this proposal on 16 July and construction began on 12 October 1934. The prototype, with the name AC3, was ready on 14 April 1935. It was tested from 4 July until 2 August 1935. Then a preseries of four was produced of an improved type, the AC4, to be tested until 27 January 1938. These first vehicles had the standard APX1 turret, fitted with the short 47 mm SA 34 gun. On 25 March 1936, the AC4 was taken on as the standard medium tank of the Cavalry with the official new name Automitrailleuse de Combat modèle 1935 S (or AMC 1935 S), when a first order for fifty was made. The tank was then more commonly known as SOMUA S35 (S again for SOMUA and 35 from 1935, the year of introduction); today the even shorter abbreviation S35 is most often used, usually with a hyphen: "S-35", but this latter form is never seen in contemporaneous French sources.
The mass-production vehicles would have the longer SA 35 gun. Originally, a total production of 600 was planned, but the second order was limited to 250 for financial reasons. Later a third prewar order of 200 was made.
DescriptionThe hull and turret were castings with a maximum thickness of 47 mm and 40 mm respectively — the former of four sections, bolted together: two longidutinal plates formed the bottom; the superstructure was divided in a front and back section. The turret was a variant of the APX 1 as used on the Char B1: the APX 1 CE (chemin élargi) with a larger (1130 mm as against 1022 mm) turret ring, allowing the radio operator to assist the commander in loading the gun from an ammunition stock of 118 shells (90 AP, 28 HE) and 2250 MG rounds. Still, as with the B1, the commander was expected to direct the tank while aiming, loading and firing the 47 mm SA 35 main gun — although at least the radio duty could be left to another crewmember. Radios were planned to be part of the standard equipment of S35s. In practice the platoon commander had an ER (émetteur-récepteur) 29 set for communications at a higher level, but a shortage of the short range ER28 sets for communication within the platoon meant that the other four tanks were never fitted with any form of radio, although in some units all tanks had antennae: the programme to fit the sets themselves was postponed until the summer of 1940 and thus overtaken by events.
The suspension was designed by Eugène Brillié, the same man who had developed the first French tank, the Schneider CA1. He had worked with the Czech Škoda company and based his design on that of the LT35: eight road wheels paired on four bogies with leaf springs and an equally large tension wheel. The first fifty vehicles had tracks consisting of 144 track links, each link with a length of 75 mm; later vehicles had 103 links of 105 mm length.
The engine was in the rear of the hull side by side with two self-sealing fuel tanks, of 100 and 410 litres respectively, separated from the fighting compartment by a firewall bulkhead. The (officially) 200 hp engine, designed by Javier-Sabin, drew fuel from the smaller tank, which was itself automatically replenished from the larger one. Inexperienced crews sometimes made the mistake of only filling the smaller tank. Engine and suspension maintenance was difficult and time-consuming, due to a poor accessibility, though this was improved in later vehicles.
The S 35 had an automatic fire extinguishing system using several tanks placed at critical spots, containing methyl bromide.
Tactical functionLike the British and the Soviets the French believed in a strict division of labour between cavalry tanks and infantry tanks. The French Army preferred to fight a defensive battle — and was convinced it would be victorious in such an engagement — but was realistic enough to understand that the strategic situation might well force it to wage offensive warfare. Each of the two phases of an offensive: the breakthrough and the exploitation of it, called for its own specialised vehicle. The SOMUA S35 was optimised to fulfill the latter role: it had good speed, an adequate range, a gun powerful enough to easily destroy its two probable opponents: the Soviet BT-7 and the German Panzerkampfwagen III and armour thick enough to be practically immune to the fire of both. So it could carry out deep strategic penetrations and destroy enemy armour reserves trying to prevent them. This is why today the S35 is often described as the best tank of the thirties. The French Cavalry would heartily disagree. They judged their main tank to be imperfect in many respects. Remarkably not included among the perceived imperfections was the one-man turret, though it is today typically mentioned as its single most important drawback. A commander was supposed to acquire such a degree of hability that his workload didn't negate the lack of need to coordinate the actions of three men in a larger turret crew or the advantage of a quicker reaction because of a superior rotation speed.
The Cavalry however did acknowledge three flaws, respectively on the tactical, the operational and the strategic level. The main tactical flaw was the hatchless cupola, forcing the commander to fight buttoned-up. This had been caused by the need to adopt the APX-1 turret, purely for budgetary reasons. The B1 bis's APX4 turret faced similar criticism from the Infantry.
The operational flaw was its poor mechanical reliability. The suspension units were too weak and too complicated, demanding enormous maintenance efforts, especially since the cast armour modules did not allow an easy access to the suspension and engine. This had been caused by the fact there was no central institution regulating French tank development. The Army branches issued very vague specifications, leaving it to private enterprise to come up with precise proposals. French machinery was often outdated and the designs reflected the limited existing production facilities. To introduce a Christie suspension — the obvious solution — was impossible without a thorough industrial modernisation and raising of quality standards.
The strategic flaw was the high unit price of the tank and the limited number of large cast sections that could be produced. This implied that the absolute number of S35s produced would be low. The tank had to be supplemented by a cheaper type and the only one available had been the Hotchkiss H35, much inferior in armour, armament and speed, even after it had been improved to the "H39" variant. The Cavalry had a very low opinion of the fighting value of this light tank. It decided to keep a large number of S35s in the core of their armoured divisions and rejected the easy method of raising more of them by dividing the S35s among the Cavalry Light Divisions — in contrast to the Germans who distributed the also low number of PzKpfw IIIs partly to their Leichte Kavalleriedivisionen. It also decided against the continued mass production of even lighter vehicles like the AMR 35 and AMC 35. This again implied that the Germans would in May 1940 have a large superiority in strategically mobile large armoured units: ten to three, because the four French armoured divisions of the Infantry did not possess sufficient organic artillery and infantry to operate effectively in an independent role. France intended to raise many more armoured divisions for use in a decisive offensive in 1941; as the French production capacity for cast armour sections was insufficient, at the time of the defeat negotiations were ongoing to employ American producers; during the crisis caused by the German attacks in June it was even proposed to let them build 2000 vehicles.
Production and operational historyFour tanks of the AC4 pre-series of the S35 entered service in January 1936 with the 4e Cuirassiers. By mid 1938 a hundred had been produced, 270 on 1 September 1939 and 246 delivered. On this date 191 served with the troops, 51 were in depot and four had been sent back to the factory for overhaul. After the outbreak of war a fourth order of 200 was made, bringing the ordered total to 700. Later it was decided that from the 451th vehicle onwards the tanks would be of the improved S 40 type. Production in fact totalled 430 by June 1940, including the prototype and the preseries. Of these about 300 were in front-line service at the beginning of the Battle of France, with the three armoured divisions of the Cavalry, the Divisions Légères Mécaniques or Mechanised Light Divisions ("light" here meaning "mobile"). Each of these had an organic strength of eight squadrons with ten S35s; each squadron however had a materiel reserve of two tanks and regimental and brigade commanders in practice had personal tanks too, resulting in a total of 88 vehicles per division. Those available in the general materiel reserve were later issued to several ad hoc units, such as the 4th DCR (commanded by Charles de Gaulle) which received 39, part of 3e Cuirassiers, the 4th DLM (10), and some Corps-francs Motorisés (about 25). Also the destroyed 1st, 2nd and 3rd DLM were reconstituted with a small number of tanks, the first two divisions received ten S 35s, the third twenty; S 35s further served with the 7e Cuirassiers (25) and a platoon of three was present in the 3e RAM of the 3e DLC.
In May 1940 during the Battle of France the DLMs had the difficult task to carry out a quick advance into the Low Countries, followed by a holding action to allow the infantry divisions following behind to dig themselves in. The 2nd and 3rd DLM were concentrated in the Gembloux gap between Louvain and Namur, where there were no natural obstacles to impede a German advance. They had to spread out somewhat to hold that sector against incursions by the German 3rd and 4th Panzer Divisions. This was necessitated by the local tactical situation and did not reflect some fundamental difference in doctrine between the use of the DLMs and the Panzerdivisionen. Both types of units were very similar in equipment, training and organisation, as the German armoured divisions too were primarily intended for strategic exploitation, while the breakthrough phase was preferably left to the infantry. The resulting tank battle from 13 to 15 May, the Battle of Hannut, was with about 1700 AFVs participating the largest until that day and is still one of the largest of all time. The S 35s gave a good account of themselves, proving to be indeed superior to the German tanks in direct combat, but they were rather hesitantly deployed as the French High Command mistakenly supposed the gap was the German Schwerpunkt and tried to preserve their best tanks to block subsequent attacks by the rest of the Panzerwaffe.
When it transpired the attack was really a feint and the forces in the north were in danger of being cut off by the German advance south of Namur, the 1st DLM that had very quickly moved 200 kilometers to the north to help the Dutch, was hurriedly rushed south again. The resulting disorder and breakdown of most of its S 35s rendered this unit, the most powerful of all Allied divisions, impotent; it was defeated by the German 5th Panzerdivision on 17 May. The other DLMs fought a delaying battle, participated in the Battle of Arras and then disintegrated. Committing its only strategically mobile armour reserve early in the battle had made the French Army fatally vulnerable to a German strategic surprise.
After the June 1940 armistice, S 35s were allowed to be sent to West Africa to bolster the hold of the Vichy regime on that region. They were issued to the 12e régiment de Chasseurs d'Afrique that, after French forces in Africa had sided with the Allies, operated them against German and Italian forces during the Tunisia Campaign. After taking part in the Tunis victory parade, 12e RCA's S35s were replaced by M4 Shermans, but crews often affixed the SOMUA plate on their new tanks.
After the liberation of France in 1944 an armoured unit was raised, the 13e Régiment de Dragons, using French matériel, among which seventeen S 35s.
Foreign serviceAfter the fall of France a number of S 35s (297 were captured according to some sources) were taken into service with the Wehrmacht as the Panzerkampfwagen 35-S 739(f). The Germans modified the cupola by cutting its top off and installing a simple hatch. On 10 December 1940 the first German tank unit equipped with French Beutepanzer was formed: 201. Panzerregiment with 118 tanks, 36 of these were S 35s, the rest "38Hs". On 10 February 1941 202. Panzerregiment was established; both regiments were united into Panzerbrigade 100. On 27 January the independent 301. Panzerabteilung was formed with French vehicles; total S 35 organic strength in the Wehrmacht was thus ninety. On 22 March this independent battalion replaced the Second Battalion of 201 Panzerregiment, which battalion was renamed to 201. Panzerabteilung and sent to Finland in June, the only German unit with S 35s that would fight on the Eastern Front. The 21st and 25th Panzerdivision in 1943 used some S 35s when reforming after having been largely destroyed. Some vehicles had their superstructure removed and were used for driver-training. There were still twelve S 35s listed as in German service on 30 December 1944.
Some of the captured S 35s were delivered to German allies: 32 to Italy in 1941, two to Hungary in 1942 and six to Bulgaria in 1943. They were used by the Italians for training purposes and to equip a reserve unit. The Bulgarian vehicles were after the war used by police units.
ProjectsFrom the S35, SOMUA developed in 1937 the SAu 40 self-propelled 75 mm gun. Its drivetrain featured an extra wheel to improve offroad capabilities, and the hull was wider. Only one prototype was built in this configuration; it fought in June, probably together with a small number of mass-production vehicles, fitted with the powerful 47 mm SA 37 gun: 72 units had been ordered on 1 May 1940.
In order to address some of the shortcomings of the S35, SOMUA presented the improved AC5 type in 1940. Based on the SAu 40 chassis, this SOMUA S40 had a welded turret and superstructure, both to lower production costs and to improve protection standards as the cast sections, delivered by eighteen subcontractors, sometimes were of inferior quality. An order was made for fifty vehicles, and it was intended to become the main production type, superseding the S 35 from the 451st vehicle, but none were completed at the time of the German invasion.
In 1945 it was proposed to build a tank destroyer by refitting existing S 35 chassis with a superstructure for the British 76.2 mm 17-pounder gun.
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