Char-8 Montbrun (Montbrun Medium Tank or AMX-34)
Development
The Montbrun's design history began in the 1930s, just prior to the beginning of the Rif-Atlas Revolt, as a result of the French Army's concern about the growth of Indian and German tank designs. At the time the Montbrun's development started in 1937, the French Army, in the form of the
Commission de Vincennes, spearheaded by General Jean-Marie Lemaréchal, had formed very decided opinions about the sort of tank they wanted. Although the French had produced a number of innovative and technically impressive tanks through the early 1930s, procurement was an issue, with small production runs and various different types of tanks leading to a high average vehicle cost and issues with parts and supplies. Lemaréchal, as an expert on motorization, determined that the French Army would only equip two types of tanks: a fast, light tank for reconnaissance, screening, and colonial use, and a balanced medium tank.
Transall's Russian and Atlantean-designed T-37 heavy tank, briefly adopted by France as the Char-2 Lefebvre, provided an initial step towards the Commission's ideal tank, but while it was well-protected and, at the time, well-armed with a 75mm/L45 gun, it had a lower speed than desired, as well as a lower power-to-weight ratio of 13.3 hp/ton and a mediocre range. Finally, it was not particularly cheap to produce, and the hull lacked the sloped frontal armour the Commission desired. For the new medium tank, the Commission de Vincennes established a series of design guidelines and then handed over the task of producing a working vehicle to a group of designers and engineers. The Commission demanded a vehicle of thirty-five metric tons or less, with a road speed of fifty kilometers an hour, a diesel engine with a road range of at least three hundred kilometers, a 75mm/L53 gun in a three-man turret, sloped armour, and a power-to-weight ratio of at least sixteen horsepower per ton. The design group was able to achieve all of these requirements. By 1939, the Commission approved the final design and extended requests for manufacturers. Renault, AMX, Somua, ACL, Lorraine, and Batignolles-Châtillon all expressed interest in manufacturing the vehicle. As Renault was then engaged in preparing for light tank production, the initial order went to AMX and Somua, with smaller batches going to ACL and ARL.
Somua undertook early production of all vehicles from April 1941 onward, as AMX was still gearing up for high-capacity tank production. Most early vehicles produced by Somua were in fact tank destroyers (the "Druout"), which no one else produced. AMX and ARL followed several months later with tank production. ACL (Ateliers et Chantiers de la Loire) also produced Montbrun variants, focusing mainly on self-propelled artillery pieces and armoured engineering vehicles.
Further development of the initial design took place during 1941 in order to ease manufacturing issues and solve problems overlooked in the initial design. In December 1941, the first major update to the tank occurred, placing a more powerful and better-balanced 75mm/L60 gun in a new turret. In early 1944, the French Army attempted to equip the next version, the Char-8A3, with an auto-loading 90mm/L54 gun in an oscillating turret; but this version was deemed to be a failure. The Char-8A3 also initiated the use of a new diesel engine, the MD.12/40, which offered slightly more power. After a pause in production, the Char-8A4 arrived in 1945, switching to a larger 82mm/L71 gun. All Char-8A3s and a number of Char-8A2s were converted to the 8A4 standard, although AMX produced a significant number of new tanks to the same design.
Variants
CDC-8 Druout Tank Destroyer
The Druout tank destroyer, built exclusively by Somua, carried a 90mm/L40 gun in a sloped casemate. In most respects, the engine, drive-train, suspension, and tracks remained the same as the Char-8A1 on which it was based. Druouts formed the core of the four
Groupes de Anti Char de Corps d'Armée, which served as the main mechanized anti-tank wing of the French Army.
DCA-8 Cyclone
The Cyclone was an otherwise standard Char-8 series tank fitted with a pair of 40mm/L60 anti-aircraft guns in a special lightly-armoured turret. This version functioned as an anti-aircraft tank.
Char-8A Series
Initial tank production focused on the Char-8A1, which carried a 75mm/L53 Mle1938 gun. This version was expected to be the standard for several years, but AMX and Somua offered a number of proposals for manufacturing improvements. Among the alternatives was a redesigned main gun, with modifications to ease loading, improve the balance of the gun, and increase the available room inside the turret for the three-man crew. A larger turret ring (175cm instead of 170cm) helped to provide more room. The modified gun, with a barrel lengthened to sixty calibers, entered service with the newly-improved Char-8A2 Montbrun in autumn of 1941. It was this 8A2 version which saw series production through 1942 and 1943. Once sufficient quantities of Char-8A2s became available, the Char-8A1 tanks were replaced, with most being converted to DCA-8 Cyclone anti-aircraft tanks. A small batch of Char-8A1s, refurbished by ARL, were given to the Philippine Army under a defense assistance scheme.
Char-8A2
In late 1943, AMX restarted production with a new oscillating turret and the 90mm/L54 gun, as well as a newly-modified engine. This variant, the AMX Char-8A3, was intended to replace the standard tanks in the armoured regiments, providing more firepower. However, crews found the oscillating turret too cramped, and disliked the need to exit the tank to reload the three-round magazine for the autoloader. To make issues worse, the 8A3's autoloader followed a much different system than the reliable 75mm/L53 autoloader installed on the Char-6D, and it established an extremely poor reputation in the field. A hundred and ninety-five vehicles were manufactured to 8A3 specifications before the French Army cancelled further orders. The failure of the Char-8A3's turret and gun left the French Army without a viable rebuild proposal for the two thousand Char-8A1s and 8A2s that had already been produced; it had been the Army's intention to upgun the entire Montbrun fleet to a 90mm gun between 1945 and 1946.
In November 1944, DEFA offered an alternative to the 8A3's oscillating turret and unreliable 90mm loading system. An experimental high-velocity Hotchkiss 82mm/L70 antitank gun, complete with a new turret manufactured by FCM, appeared with the Char-8A4 upgrade. The new turret and the smaller gun were backwards compatible with the turrets of previous models, allowing older tanks to be refitted to the new 8A4 standard. Starting in February of 1945, SOMUA began refitting all 8A3 Montbruns with the new turret; older but more reliable 8A2 tanks were rebuilt on a larger scale (with new MD.12/40 diesel engines, drive components and new electrical systems) later in 1945. As part of the 8A4 upgrade, major improvements were made to the engine compartment, installing the engine and several other major components on sliding rails to allow for the tank's diesel engine to be removed more easily for maintenance and replacement. This halved the amount of time necessary for major engine maintenance. A small opposed-cylinder diesel engine, generating thirty horsepower, was also added. This engine did not cover the vehicle's propulsion, instead generating electrical power for turret rotation and other systems. The smaller engine could also warm and crank the main diesel engine. Armoured sideskirts, which were used irregularly on the Char-8A2, became standard in order to protect the tank's running gear from antitank rockets and light weapons. Another unusual modification added with the Char-8A4 was the addition of a simple latrine under the loader's folding seat.
Char-8A2 rebuilt as Char-8A4.
Char-8C Series
The Char-8C tank variants served as squadron command tanks (with each tank company fielding two Char-8Cs). The Char-8C was mechanically indistinguishable from the Char-8A series tanks, and the French went to some effort to keep these command tanks looking identical to the regular vehicles. However, there were some differences internally. The Char-8C1 traded a rack of MG ammunition and three main gun rounds for an enhanced transmitter-receiver set, so that the vehicle commander (and company commander) could maintain control of his squadron through communication with the regimental headquarters and the platoon leaders. Capabilities were increased in the Char-8A2, which featured a larger, more capacious turret and did not have to trade as much internal space for the radio equipment. In the Char-8C2, a jumpseat was added for a fifth crewman who could assist in operating the radio.
Engines
Alsthom MD.12/36
The engine originally used on the Montbrun was the Alsthom MD.12/36, a 36-litre V-12 diesel engine derived from the Hispano-Suiza HS-12Y aircraft engine. This engine was developed following the French Army's experience with the Russian-designed Kharkiv model V-2 diesel, which was used in the Char-2 heavy tank, and license-built in France. The MD.12/36 adapted a number of design cues from the Russian Kharkiv, but represented a completely indigenous development. From 1943 onward, the MD.12/36 was replaced by a follow-on derivative, the MD.12/40, one of the "Series Three" engines.
Alsthom MD.12/40
The MD.12/40 diesel engine was one of Alsthom's "Series Three" diesel engines, a family of diesel engines which included a V-6, a V-8, and a V-12, all using similar parts and cylinder sizes. The Series Three is designed to operate on a variety of fuels, including both regular diesel fuel, automotive petrol, kerosene, and vegetable oil (including a mix created using the Arachide or ground-nut grown in Africa). Alsthom intentionally tried to design the engine to accept a wide variety of fuels in order to avoid difficulties with fuel availability when the vehicle was used in service outside the French Metropolitan region. Use of the MD.12/40 engine started with the Char-8A3 Montbrun, although Char-8A2s were converted to use the engine during conversion to the Char-8A4 standard. All of the MD.12/40 engines used on the Char-8A4 Montbruns (but not the upgraded Char-8A3s) were fitted with a turbocharger.
Other Engines
Several Montbruns were used in various experiments with different motive power systems. One of the most novel experiments occurred in 1944 when a prototype gas-turbine unit of 560 horsepower was installed in place of the normal V-12 diesel engine, making the Montbrun the first tank to be powered by a gas turbine. While the engine was suitable for mass-production, fuel economy was significantly reduced, and the French Army gave no serious consideration to standardizing it further. The turbine-powered Montbrun remained in service at the Armoured Cavalry Branch's school in Saumer as a testing vehicle.
Another experimental variant which saw more widespread use was an Alsthom "Series 3" W-16 engine. This engine mounted a pair of Series Three MD.6/27 engines (each two-thirds the size of an otherwise-standard MD.12/40) together in a 'double-vee' setup. This turbocharged engine provided an outstanding 906 max horsepower. The engines were manufactured under contract by Bugatti and fitted to Montbruns of the
Régiment de Dragons de Marine in 1945. These tanks, manufactured by Batignolles-Châtillon and officially designated the Char-8E1, were dubbed "Guépards" by their crews for their acceleration (although speed was limited to prevent damage to the drive train). Emulating the French Air Force's elite 1/2 Escadron de Chasse, the Regiment adopted a similar badge, with three running cheetahs, one representing each tank squadron in the regiment.
Char-8E1 Guépard; also roughly representative of the Char-8A4bis.
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Variants
Char-8A Series - The standard tank model.
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Char-8A1 Montbrun: Standard (base) vehicle with 75mm/L53 gun.
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Char-8A2 Montbrun: Standard (base) vehicle with 75mm/L60 gun.
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Char-8A3 Montbrun: Tank equipped with 90mm/L54 gun in oscillating turret and MD.12/40 diesel engine. Weight rises to 35 metric tons. Introduced January 1944.
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Char-8A4 Montbrun: Rebuilt Char-8A2s and Char-8A3s equipped with 82mm/L71 gun; otherwise identical to Char-8A3. Introduced February 1945.
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Char-8A4bis Montbrun: New-built Char-8A4 (see above). On new production, the turret was moved slightly aft and the driver's station received three view periscopes. Introduced March 1945.
Char-8B Series - A Char-8 variant designed as an assault tank. None were ordered.
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Char-8B1 Montbrun: Uparmoured vehicle equipped with a 105mm/L28 howitzer in modified turret. One prototype built.
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Char-8B2 Montbrun: Otherwise standard Char-8B tank with flamethrower substituted for 20mm gun. Intended as an "assault tank". One prototype built.
Char-8C Series - The standard tank model equipped with extra radios. These vehicles are otherwise standard variations of the 8A series.
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Char-8C1 Montbrun: Standard command tank with 75mm/L53 gun. (Equivalent to Char-8A1.)
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Char-8C2 Montbrun: Standard command tank with 75mm/L60 gun. (Equivalent to Char-8A2.)
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Char-8C3 Montbrun: Command tank equipped with 90mm/L54 gun in oscillating turret and MD.12/40 diesel engine. Weight rises to 36 metric tons. Introduced January 1944. (Equivalent to Char-8A3.)
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Char-8C4 Montbrun: Rebuilt Char-8C2s and Char-8C3s equipped with 82mm/L71 gun; otherwise identical to Char-8C3. Introduced February 1945.
CDC-8 Druout Series - The original vehicle chassis of the series, designed as a casemate-style tank destroyer.
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CDC-8 Druout: Tank destroyer equipped with a 90mm/L40 anti-tank gun in a casemate. The Druout preceded the Char-8A into service. 270 vehicles built.
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CDA-8A, B Chasseloup: Assault gun based on the Druout hull, equipped with a 105mm howitzer (CDA-6A) or a 155mm heavy mortar (CDA-6B) in a casemate. 113 built.
CA-8 Gribeauval Series - The Gribeauval is a series of self-propelled artillery pieces built on the common hull.
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CA-8A Gribeauval: Self-propelled gun equipped with a 75mm howitzer. 45 vehicles built.
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CA-8B Gribeauval: Self-propelled gun equipped with a Canon de 105mm modele 1936 (105mm/L38). 270 vehicles built.
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CA-8C1 Gribeauval: Self-propelled gun equipped with a Canon de 155 mm GPF (L/38) 155mm howitzer. 90 vehicles built.
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CA-8C2 Gribeauval: Self-propelled gun equipped with an Obusier de 155 mm Modèle 44 howitzer. 90 vehicles converted from CA-8C1; 180 vehicles converted from CA-8B.
Marescot Series - The Marescot is a series of armoured engineering vehicles built on the common hull.
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VBG-8A Marescot: An armoured engineering vehicle with a dozer blade, digger, and 100mm demolition gun. 135 vehicles built.
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VBG-8B Marescot: An armoured engineering vehicle with a dozer blade, winch and crane for vehicle recovery. 67 vehicles built.
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PP-8 Marescot: An armoured engineering vehicle equipped with a scissors-style ten-meter bridge with a weight limit of 36 tons. Entered service in 1943. 60 vehicles built.
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VD-8A, B Marescot: An armoured engineering vehicle (similar to the VBG-8A) equipped with a mine-flail (VD-8A) or mine rollers (VD-8B).
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VBA-8A, B Boeufs: Auxiliary vehicle adopted as cargo vehicle for the CA-8D self-propelled gun (VBA-8A), and as a bridge carrier (VBA-8B).
Cyclone Series - The Cyclone is a series of anti-aircraft tanks built on the common hull.
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DCA-8A Cyclone: An anti-aircraft tank equipped with two Hotchkiss 25mm AA guns.
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DCA-8B Cyclone: An anti-aircraft tank equipped with two 40mm AA guns.