Char D1
The Char D1 was an Interwar French light tank.
The French plan of 1926, calling for the creation of a Light Infantry Support Tank, led to the development of the existing Renault NC1 prototype into the Char D1. One hundred and sixty vehicles of this type were produced between 1931 and 1935. There was a pre-series of ten vehicles and later 150 standard vehicles were built. Until 1936 the vehicles were fitted with Renault FT turrets because the intended cast ST2 turrets were not yet ready. The ST2 turret was armed with a short 47mm SA34 tank gun with a coaxial 7.5mm machine gun. The hull carried a 7.5mm MG in the bow. The type did not serve as an infantry support tank as originally intended, but as France's major battle tank of the early 1930s; it was quickly phased out in 1937 because of its mechanical unreliability and relegated to colonial units in North Africa.
Development
After World War I, France possessed a very large fleet of Renault FT light infantry support tanks. Although many of these were sold to other nations, over 2800 remained. In contrast to the United Kingdom, which greatly reduced its armoured forces and scrapped redundant AFVs after the war, France maintained a large number of active or reserve armoured units and all of the remaining Renault FTs were kept in working order. This implied that in the early twenties France had the strongest and most modern armoured force in the world, but this very fact led to a state of complacency. Development of new tank models was not seen as urgent, and budgetary restraints would for the immediate future prohibit any further tank production. When in 1922 General Jean Baptiste Eugène Estienne concluded an official study containing guidelines for long term tank design, no provisions were made for any new light infantry tank.FT Kégresse
The remaining Renault FT vehicles, though having shown themselves to be very effective in trench warfare, were not well adapted in their present state of technological development to peacetime conditions. The main problem was their low top speed, which necessitated special tank transporters whenever the vehicles had to be moved outside their base area and made them fundamentally unsuited to patrolling duty in the colonies. It was therefore decided to modify a number of existing vehicles, by fitting them with a more effective suspension system. The first modifications were of the Renault FT Kégresse-type, which featured the suspension of the Kégresse half-track, fitted with a special rubber steel-reinforced track. In 1925 42 vehicles were rebuilt this way and deployed in 1926 during the Berber insurrection in Morocco. The modification allowed for a top speed of 17 km/h but field experience showed that the track was liable to suddenly snapping at top speed with often catastrophic consequences and the modification project was therefore discontinued. Modified tanks continued to be used by the 508e BCC, their tracks improved by rubber-metallic grousers. Nine Renault FT Kégresse vehicles were later sold to Yugoslavia and five to Poland.Renault NC
Meanwhile, Louis Renault had obtained an order in 1923 to build two new prototypes as a parallel modification project, with the factory designation Renault NC; it was intended to feature not only an improved suspension system but also a more powerful engine. Like "FT", "NC" is a combination of code letters devoid of any meaning. One prototype happened to be finished second, in December 1925, and was therefore called the NC2. It was fitted with a modified Kégresse leaf spring suspension and a 62 hp engine. It had as an alternative designation Renault Modèle 24/25, because Renault proposed to build it as a possible "fast tank" as specified in Plan 1924 of the French Cavalry. This line of development was discontinued however. The first prototype to be ready, thus named the NC1, had a different suspension system, with twelve wheels and three large vertical coil springs per side. It allowed for a top speed of 18.5 km/h, making it in 1926 the fastest French tank ever developed.As had been the case for the Renault FT Kégresse, this project was still primarily intended to result in a modification proposal to rebuild existing Renault FTs. In 1926 it transpired that the Char de Bataille project, that later resulted in the Char B1, was evolving into a far heavier tank than at first intended. It would be impossible to procure this heavier design in sufficient numbers and therefore specifications were made in the Infantry Plan 1926 for a new Char léger d'accompagnement d'infanterie, a "light infantry support tank". Renault immediately tried to offer his NC as the logical candidate for this role.
NC31
In 1928, Renault succeeded in his attempt to get his Renault NC accepted as the basis for further light infantry tank development; he was granted an order to build two prototypes. The Army called this project the Char D, Renault used the designation NC28. Of the two prototypes, the first was fitted with the twin machine gun turret of the SRA Char de Bataille prototype. Also a new suspension system was tested incorporating the special chenille légère designed by Colonel Balland, which was optimised for high speeds. As this vehicle was a derivative of the NC1, it was later indicated with the designation NC2, creating confusion with the earlier project of that name; many later books assumed they were one and the same vehicle, repeating mistakes in the 1935 edition of Heigl's Taschenbuch der Panzer. The Army made a choice in March 1929 for the second prototype, the NC3 gun tank, and ordered a pre-series of ten vehicles in December 1929. These had the Renault factory designation NC31, after the intended year of delivery. Renault merely had to build the hulls at a price of 400,000 FF each; the cast turrets were, as usual in France, separately ordered with the Schneider company; they were of the ST1 type. As this turret was much wider than the Renault FT turret used on all previous NC models, Renault broadened the hull accordingly; the typical tapering nose point of the Renault FT was abandoned. The ten hulls were delivered between May and November 1931: after an interval of ten years after the delivery of the last Char 2C in 1921, French tank series production for the home market was thus resumed.The ten pre-series hulls were tested by the 503e Régiment de Chars de Combat. Many shortcomings were discovered by the Commission de Bourges, the French Infantry matériel commission. Steering was difficult, the suspension too weak and the exhaust pipes overheated the engine compartment. Nevertheless, the type was accepted for mass production — the commission had little choice in this as the main series had already been ordered — provided that changes were made. The strangely squeezed ST1 turret, the first ten of which were delivered from November 1930, was rejected though as being unacceptably cramped and unbalanced. To avoid having to lower the gun breech into the fighting compartment each time the gun was loaded so as to allow a round to be inserted, the main armament had been placed in a very forward position. The ST1 turrets were therefore removed from the first ten vehicles.
Char D1
On 23 December 1930, a first order of 70 main production series vehicles was made, followed on 12 July 1932 by a second order of 30; the last order on 16 October 1933 was of 50 vehicles, for a total of 150, delivered between January 1932 and early 1935, at a price of 375,000 FF per hull. Including the NC31s the series numbers were 1,000-1,160. The factory designation was still Renault NC.The series vehicles had many improvements: a Cleveland differential; a 74 hp instead of a 65 hp engine; the exhaust pipes were placed to the right, no longer crossing the engine room and there were support rollers fitted to prevent resonance in the top track run. Finally, the fuel tank was enlarged to 165 litres and a new radiator was fitted.
In May 1930, Renault was asked to develop two derived types, the Char D2 and the Char D3; the original Char D now received as designation '''Char D1.'''
Belgian production plans
In 1931, it was generally expected that Belgium would soon start to replace its ageing Renault FTs. Early 1932 the Belgian company Cockerill, based at Seraing near Liège, approached Renault to inform whether it could take the Char D into licence production, purely for the Belgian market. Louis Renault in turn on 25 March 1932 asked permission from the French Ministry of Defence to allow Cockerill to produce a French tank, arguing that the close military ties between the two nations favoured such an undertaking. On 13 April the Ministry answered that Renault seemed to have forgotten to indicate to which type exactly his request pertained, though this matter was quite relevant "given the secret character presented by certain of your matériel". Three days later Renault admitted that he had referred to the Char D, "older matériel obviously being incapable of interesting that nation". In that case, the ministry replied on 21 April, it regrettably had to withhold its permission: no types more modern than the Renault FT or NC could be destined for licence production. The main objection was that the secrets of the cast armour technology of the ST-turret should not be compromised.Renault tried to overturn this decision by lobbying with his army contacts. On 26 April he noted that General Maurice Gamelin had promised to use his influence to promote Renault's project; the next day, however, it transpired that the deputy chief of the general staff General Joseph-Edouard-Aimé Doumenc had vetoed the idea, with the argument that, apart from the secrecy problem, it was best to keep the employment in France. Renault protested that Belgium would not import tanks anyway, in view of its balance of payments difficulties and that "if we don't do it, Vickers will", but on 29 June had to report Cockerill that the plans could not proceed; he suggested that Belgium simply import his tanks, but in fact it was indeed the British Vickers company of which the models would be taken into licence production by Belgium.