Later Designs: The Schneider CA2, CA3 and CA4
The first projects to create new variants were based on the original Schneider CA design. In September 1916 Estienne wrote a memorandum outlining his thoughts about a possible command tank. Considering that tank units would not only attack static enemy positions but also had to manoeuvre on the battlefield against moving hostile troops, he foresaw that their commanders would need more agile vehicles with armament and armour concentrated in the front, to lead a pursuit or cover a retreat. Therefore a variant was needed fitted with a turret featuring a 37 or 47 mm gun, protected by 15 mm front armour, with a crew of four and with a top speed of at least 10 km/h. Fifty such vehicles should be constructed. Towards the end of 1916 a mock-up was ready under the designation of Schneider CA2. On 26 and 27 March 1917 a prototype was tested at Marly. It had the standard suspension of the Schneider CA but its hull was strongly shortened so that the overhanging nose had disappeared. The 75 mm cannon had been replaced by a cylindrical turret, intended to be armed with a 47 mm gun and a machine-gun, close to the rear of the hull. The hull was further diminished in size and weight by a considerable narrowing and closing of the roofed skylight slit, which lowered its height. During the testing the vehicle, though no longer getting itself stuck on an overhanging nose, still proved unable to climb out of muddy shell craters. It was concluded that the suspension should be lengthened by the equivalence of three track links, about forty centimetres, and on 13 April 1917 a quick commencement of production was envisaged. In reality Estienne had already on 22 March decided to discontinue this project in favour of a Renault FT command (signal) version. The CA2 prototype was subsequently used as a training and test bed vehicle and the immediate need for command vehicles was met by fitting two standard Schneider CAs with radio sets.
Early 1917 it was suggested to construct some vehicles as flamethrower tanks by installing a flamethrowing device in two armoured turrets, one at the left front corner and the other at the right rear corner, each having a field of fire of about 180°. The fuel reservoirs would be inside the hull. No actual production resulted. In February 1917, Schneider proposed to build a variant with a thirty-two centimetres wider hull fitted in the front with a 47 mm gun and two machine-gun turrets placed diagonally behind the driver position, while the engine was relocated to the rear of the vehicle. On 2 April 1917 the Ministry of Armament asked Schneider to design two improved versions of the Schneider CA: one with a gun turret, the calibre not surpassing 47 mm if it were a long gun; the other with a long 75 mm gun in the front of the hull.
After the failure of the Nivelle Offensive, Schneider understood more capable designs had to be manufactured if the tank were to remain a viable weapon system. On 1 May 1917 it discussed a range of possible options, numbered one to five. All had in common that basically the same mechanical components were used as with the Schneider CA, though often improved, and that the suspension was only partially changed: elongated by the addition of an eighth road wheel and using thirty-five instead of thirty-three wider, forty-five centimetres broad, track links. However, all were also strongly modernised: the hull overhang had disappeared, the hull front formed as a sloped wedge, and the inner space was compartmentalised, with an engine room, protruding behind the sprocket, at the back and the driver in front. The armour base was about sixteen to twenty millimetres. The first two proposals were probably identical to the April 1917 projects and discarded by the company as inferior. The last three, favoured by Schneider itself, were all turreted vehicles: design No 3 had a 47 mm gun in the hull and a single machine-gun turret; No 4 differed in having two machine-gun turrets and No 5 in having the gun moved to a turret. During discussions about these proposals, Estienne pointed out that the intended long 47 mm gun had not entered production yet and that no high performance explosive charge was available to give it a sufficient effect on soft targets. Therefore he insisted on fitting the standard 75 mm field gun, even if this would raise weight to 14.5 tonnes. A week later Schneider presented proposal No 6, which envisaged a vehicle weighing fourteen tonnes and having a shortened 75 mm gun in the turret. On 5 July 1917 drawings were ready of the type, which was now called the Schneider CA3. However, these included an alternative version with a shortened 75 mm gun in the hull. Estienne had misgivings about this project, questioning its trench-crossing capacity and predicting engine power would be insufficient, given a weight that had by now reached 16.6 tonnes. Also he demanded a gun sight allowing some fire-on-the-move capability. Nevertheless, on 24 July the Consultative Committee of the Artillerie Spéciale decided that the four hundred vehicles of the Schneider Modèle 1917 ordered on 10 May 1917, were to be of the CA3 type. A prototype was ordered of each version — the mechanical parts in May and the armour hulls in July — but the company itself limited its construction activities to the one with the gun in the hull, probably because a cannon turret was judged to be "absurd" given the lack of enemy tanks and a machine gun turret was seen as necessary for close defence against infantry assault. Later that year, in an official answer to an inquiry by parliamentarian Paul Doumer regarding the progress achieved within French tank development, the designation "Schneider CA4" is used to indicate a design studied within the context of a larger order for two prototypes, weighing twenty tonnes and fitted with a cannon turret armed with the shortened 75 mm gun, and of which Schneider is unable to predict when the single prototype to be constructed would be finished, though deliveries could start in April 1918. A mock-up was built of the Schneider CA3, and on 24 October the chassis was tested at SOMUA. During the summer however, Estienne and Pétain had become worried that the medium tank production might become an obstacle to the planned light tank mass production of the Renault FT. On 27 October the committee advised that the construction of the Schneider CA3 would be suspended in favour of light tank production. It argued that the type could probably not be delivered before August 1918 anyway, too late for the summer offensives of that year, and that an improved medium tank design should be taken into development instead. The ultimate decision not to produce the Schneider CA3 was only taken in February 1918. On 19 January 1918 it was proposed that the preproduced CA3 components would be used to construct a further two hundred Schneider artillery tractors. On 3 November 1917 the order for the Schneider CA4 prototype was annulled. The new medium tank project had already been started on 15 August 1917 and strived for a technically advanced seventeen tonne vehicle armed with a shortened 75 mm gun and benefiting from a much improved mobility. It remained a paper project.
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