FCM F1 The FCM F1 was a French super - heavy tank developed during the Interbellum by the " Forges et Chantiers de la Méditerranée " company . Twelve were ordered in 1940 to replace the Char 2C , but France was defeated before construction could begin , a wooden mock - up being all that was finished . The FCM F1 was large and elongated , and had two turrets : one in front and one in the back , with a single high - velocity gun in each turret . The rear turret was higher so it could shoot over the first one . The vehicle was intended to be heavily armoured . Its size and protection level made it by 1940 , at about 140 tons the heaviest tank ever to have actually been ordered for production . Despite two engines its speed would have been low . The primary purpose of the tank was to breach German fortification lines , not to fight enemy tanks . The development path of the FCM F1 was extremely complex , due to the existence of a number of parallel super - heavy tank projects with overlapping design goals , the specifications of which were regularly changed . For each project in turn several companies submitted one or more competing proposals . The " Char Lourd " . In the twenties France used a typology of tanks , classified according to weight . The heaviest class was formed by the " Char Lourd " , or " heavy tank " . In the programmes of 1921 and 1930 , no new tank was foreseen for this class , the Char 2C fulfilling the role of " Char Lourd " . The programme of 1926 led in 1928 to a " Char d ' Arrêt " project of fifty tons ; when conceptual studies by FCM had reached 100 tons , a new plan was started in February 1929 for a somewhat lighter 65 ton vehicle , but this was terminated on 17 May 1929 for budgetary reasons . On 4 May 1936 however , the " Conseil Consulatif de l ' Armement " under General Julien Claude Marie Sosthène Dufieux decided to develop a new heavy tank , with the following specifications given on 12 November 1936 : a maximum weight of 45 metric tons , immunity to 75 mm AP fire over a distance of 200 metres , a speed of 30 km / h , a range of 200 kilometres , and an armament consisting of a long 75 mm gun in the hull and a 47 mm gun in a turret . It would thus have resembled an oversized Char B1 , of which tank several other development projects were ongoing . In 1937 three manufacturers , AMX , ARL and FCM , presented prototype proposals ; ARL even presented three of them simultaneously . All of these however even in this early stage of development had a higher projected weight than 45 tons — and threatened to become even heavier during actual construction . In reaction , the " Conseil Supérieur de la Guerre " initially decided on 26 March 1937 to build a very small and cheap but heavily armoured ( 60 mm ) vehicle instead , on the lines of the British Matilda I . The first designs featured a 37 mm gun . When a better armament was demanded , it was understood through a study by the " Section de l ' Armement et des Études Techniques " ( SAET ) on 5 April 1937 that the tank would still weigh about twenty tons , while another tank , the Char G1 , was already in development in this weight class . As a result , in February 1938 the specifications were again radically changed , and now called for a superheavy tank with a 75 mm gun in a turret ; no weight limits were imposed . Of all projects , the new specifications were most similar to the original FCM proposal of sixty tons and so the French Supreme Command decided on 6 April 1938 to grant FCM a development contract for what was now called the Char F1 . It was nonetheless realised that this project could be no more than an intermediate step in heavy tank design ; already , also in February , a special commission had been formed , headed by the inspector - general of tanks , Julien François René Martin , to further study the problem of overcoming the new defences of the " Westwall " ( often incorrectly called the " Siegfried Line " ) being constructed at the time on the western German border . The " Char d ' Attaque des Fortifications " . The commission immediately revived the " Char Lourd " concept but applied it only to the " 45 ton tank " project and differentiated this from a tank optimised for destroying modern fortifications , a " Char d ' Attaque des Fortifications " . This latter vehicle should have a powerful high velocity gun in a turret but be itself immune to enemy antitank - guns . Speed was considered of secondary import and might be as low as 10 km / h maximum . However trench - crossing and wading abilities would have to be excellent . If this should result in an overly cumbersome vehicle , it should be made modular so that the components could be transported separately . On 4 May 1938 the " Direction des Fabrications d ’ Armement " proposed to call this the " Char H " project , to distinguish it from the " Char F " , but this was rejected as there was some danger of confusion with the Hotchkiss H35 . The French High Command approved the commission ' s plans in April 1938 and proceeded to appoint a second commission to work them out in detail . This new commission was also charged with considering the question of whether a 45 ton vehicle might not after all be sufficient . In its first meeting , on 9 May 1938 , the commission quickly came to the conclusion that to meet the tactical demands a 75 mm gun in a turret and 120 mm allround armour was necessary ; this could not be reconciled with a weight of 45 tons . On the other hand , a design to equal the climbing and crossing mobility of even the old Char 2C would likely result in a 150 - 200 ton behemoth , of which even the components of a modular design would be impractical to transport . It was therefore decided to further research the possibility of a 65 ton vehicle , with an empty hull weight of 45 tons . In its second meeting on 22 July 1938 , some troubling data were considered . Most bridges could carry a maximum single vehicle load of 35 tons , so the new tank would have to cross rivers on special pontoons . German tank moats transpired to have a width of about seven metres , so a very long vehicle seemed to be necessary . Existing rail road cars could carry a maximum of 100 tons though . It was also pointed out that 120 mm armour might not be enough in view of the powerful German 88 mm gun . The commission rejected the " char minimum " proposal of 56 tons as it had insufficient trench - crossing capacity . It also discarded a proposal by the engineer Boirault to build a futuristic 120 ton articulated tank . It retained two options : the " char maximum " of 89 tons , demountable in two sections , and the " char squelette " of 110 tons and with a trench - crossing ability of eight metres ; this latter design was along the general lines of the World War I American Skeleton Tank , but with the added feature that the main body could move in relation to the skeleton track frame in order to shift its point of gravity . In September 1938 the Supreme Command ordered to immediately start research by the French industry into both possibilities . The ARL company was granted a development contract for the " char maximum " , the first proposal for which was presented by ARL in May 1939 . It had a proposed weight of 120 tons , consisted of two detachable modules and could be armed with either a gun or a flamethrower . The commission decided that only the guntank would be considered , but that a second turret at the back was needed for defence against infantry assault . It also remarked that the project was quite similar to that of the Char F1 and that perhaps both programmes should be merged . Second World War . September 1939 Programme . When the Second World War broke out in September 1939 some hurried measures were taken to have an operational heavy tank ready for the planned offensive against Germany in 1941 , even though the French High Command did not have great faith in the super - heavy tank project and intended to circumvent the " Westwall " by violating the neutrality of the Low Countries , should these refuse to join the Entente in time . The skeleton tank , being too futuristic , was abandoned . Despite the hurry , the lack of real progress made did not allow for a concentration of all effort into a single design , as it was still unclear whether a working prototype could be provided in time . Three companies , FCM , ARL and AMX , were therefore in October ordered to construct two different prototypes each , for a total of six models . These should fit existing railway wagons , which the F1 did not . The flamethrower option should be abandoned . On 22 December 1939 more precise specifications were made . FCM should complete the F1 with a 75 mm gun but also build a F1 hull with a 90 or 105 mm gun in the superstructure , because the 75 mm gun was likely too weak . As the Char F1 was designed with 100 mm armour , this should be enhanced on the front to 120 mm . A secondary turret with a 47 mm gun should protect the back . Both AMX and ARL should build prototypes with 105 and 90 mm guns in a turret — the turrets themselves being independently designed , as usual for French tanks — and a secondary turret with a 47 mm gun . That month both FCM and ARL indicated that they expected to begin construction of the prototypes in the summer of 1940 and series production at the end of 1941 ; for AMX it was too soon to make any precise predictions . ARL on 17 January 1940 ordered four turrets from the Schneider company , but it agreed only to build two 105 mm gun turrets and refused the two 90 mm gun turrets , as there was simply no capacity to manufacture them . In February 1940 the " Société d ’ Études et d ’ Application Mécanique " ( SEAM ) proposed a tank designed by the Polish engineer Prince André Poniatowski . It was a truly gigantic vehicle , weighing 220 tons , to be moved by two Hispano engines of 925 hp each , via a petro - electrical transmission . The project tried to recommend itself by pointing out that the hull was over five meters wide while being only twelve metres long and thus had a superior length - width ratio , facilitating steering . For transport the vehicle could be split in two sides along its entire length . Unsurprisingly , on 20 April 1940 it was refused by the Ministry of Defence . On 4 March 1940 a new subcommission to supervise the heavy tank design learned that the 90 and 105 mm gun turret designs were ready , i . e . on paper . It decided to abandon the AMX projects as they were hopelessly behind schedule ; its " Tracteur C " could not be ready before July 1941 . AMX terminated development on 1 April . The subcommission advised to go ahead with both the FCM F1 and the ARL prototypes and immediately place an order for ten or fifteen of the former . That advice was given to a new overarching Commission of Tank Study , to which ARL presented a wooden mock - up on 11 April 1940 ; FCM presented one the next day . It transpired that the FCM project was far more advanced and could show the new tank in every detail . The design had a sloped armour front plate , a small turret in front , instead of behind as specified , and a higher turret at the back , able to hold a 90 mm gun instead of the specified 75 mm gun . The tank had a projected weight of 140 metric tons , to be moved at 24 km / h by two 550 hp Renault engines via an electrical transmission . The Commission decided to abandon the ARL projects and make a preliminary order for twelve FCM F1s , to be delivered from May 1941 onward at three or four tanks a month . This expectation to have some tanks ready for the summer of 1941 was a very important consideration , as the entire heavy tank project faced strong opposition from those who saw it as a waste of scarce resources , better spent on building more Char B1s . The Commission also asked FCM to bring the armour protection to 120 mm all - round , though this would increase weight to 145 tons and reduce maximum speed to 20 km / h . For the commission this was a departure from its earlier decisions about a future " Char de Forteresse " . The " Char de Forteresse " . On 28 February 1940 a new commission for the study of tank design was established , the " Commission d ' Études des Chars " , to create a coherent policy for future French tank production . The commission planned for three weight classes , the heaviest of which was the " Char de Forteresse " . This tank was envisaged as a sort of " Super Char B " with a 135 or 155 mm howitzer in the hull and a 75 or 90 mm gun in the turret . Its armour should be 100 or 120 mm all - round . Nevertheless its weight was very optimistically expected to be around 80 - 100 tons , powered by a 1000 hp engine . On 14 May it was decided that , there being no suitable 135 or 155 mm gun available , the project would be dropped . Aftermath . After the Fall of France all official design on heavy tanks was halted . The Char F1 showed quite a few similarities though to the ARL 44 , produced just after the war . In 1944 the Allies had developed some new vehicles with exactly the same purpose as the FCM F1 : to breach the " Siegfried Line " . The British had the Tortoise heavy assault tank , the Americans the T - 28 Super Heavy Tank . Both designs were self - propelled guns however , not multi - turreted tanks , allowing them to be lighter and still better protected . Like the FCM 1 they would not be placed into production .