When the First World War ended there were, broadly speaking, two categories of tanks. One consisted of tanks of 20 to 40 tons which were armed with guns of 57 to 75mm and which were intended for assaulting or breaking through enemy positions. The other category consisted of lighter tanks, which ranged in weight from 6.5 to almost 20 tons but which were armed only with machine guns or, at most, with 37mm guns. The great majority of them and in particular the Renault FT and its derivatives were intended for close infantry support.
Before the war ended much heavier tanks began to be developed in France and in Germany. In France this led to the 2C tanks of 68 tons, each of which was manned by a crew of 12 and was armed with a 75mm gun mounted, for the first time, in a turret. However, only ten of these tanks were completed, after the war In Germany construction began of two K-Wagen, which weighed about 150 tons and which were armed with four 77mm guns, mounted in sponsons. Each was to be manned by 22 men but both were destroyed after the war when they were about to be completed. The 2C tanks remained in service with the French Army until 1940, when they were destroyed without ever going into action but for two decades they were the heaviest tanks in use anywhere.
Nothing more was done about the development of tanks as heavy as this after the First World War when armies were generally concerned with much lighter vehicles. In particular, the French Army planned to develop a replacement for the Renault FT. But a successor to it. the Renault R-35 light tank, was not put into production until 1935. With a maximum speed of 20 km/h it was significantly faster and the maximum thickness of its armour was 40mm instead of 20mm. But the general concept of the two-man R-35 was much the same as that of its predecessor and its main armament consisted of the same short-barrelled 37mm gun as that mounted in the Renault FT. This showed a remarkable lack of concern about the most important characteristic of tanks, which is their armament, and made the R-35 virtually incapable of fighting other tanks.
Much more sensibly, the French Army also embarked on the development of a char de bataille armed with a 75mm gun, albeit mounted in the hull. But this was not put into production until 1934 in the form of the 27 ton Char B. I, which was quickly made obsolescent by the appearance of other, more recently developed tanks.
Better progress was made in Britain. It started with the recognition by the engineering staff of the Tank Corps that the speed of tanks could be increased by the use of sprung suspensions, which none of the British war-time tanks had, and by the use of higher powered engines. This led to the design of the 20 ton Medium D, which had a higher power-to-weight ratio than any previous tank and a maxi- mum speed of about 30 km/h, or more than twice the speed of any British or French tank built until then. But even this was improved upon by the 8 ton Light Infantry Tank derived from the Medium D which, on trials in 1922, attained a speed of 48 km/h. The two tanks represented therefore a considerable advance in mobility and they were also amphibious, at least to the extent of being able to swim across calm inland waters. But their design also incorporated a number of dubious features. These included a suspension consisting of a cable interconnecting all the road rollers on each side and a single spring, pivoted track plates in the case of the Medium D and laterally flexible tracks with spherical joints between the track plates in the case of the Light Infantry Tank. Moreover, both had fixed turrets and although some of the Medium D were to have a 57mm gun the rest were to be armed only with machine guns. What is more, the maximum thickness of their armour was only half that of the Renault FT. As fighting vehicles they therefore left much to be desired but it was mechanical troubles and financial stringency which led to a decision in 1922 to abandon them.
At the same time the British Army decided to order the second of two tanks designed by Vickers Ltd. as competitors to the Light Infantry Tank. This tank, which became known as the Vickers Medium, was not quite as fast as its competitor but it was capable of about 30 km/h, which put it well ahead of most contemporary tanks and enabled the Royal Tank Corps to take a lead in the development of more mobile methods of employing tanks. Its high speed was made possible by a properly sprung suspension and it was sensibly armed with a 47mm gun. What is more, in contrast to the one-man turrets of the tanks being developed in France, its turret accommodated a gunner and a commander who, being free of the task of firing the gun. could better exercise his craft. On the other hand, it suffered from the contemporary preoccupation with machine guns, having as many as six of them which could hardly be operated by its five-man crew. Also its armour was at first only 6mm thick. Nevertheless, in spite of its various shortcomings and the criticism levelled at it at different times, the Vickers Medium represented an important step forward in the development of tanks. It was also the only tank produced in quantity during the 1920s anywhere in the world, even though the total was not more than about 160 vehicles.
After the Vickers Medium entered service attention in Britain turned to much lighter vehicles. These were conceived, like the Renault FT, as small, light tanks for use with or by the infantry. But after a number of vehicles was tried between 1925 and 1927 it was decided that there was a need for two different light armoured vehicles: one was a machine gun carrier for the infantry and the other a reconnaissance tank, with a turret, for the armoured units.
Financial considerations, which made the relatively cheap light tanks so attractive to armies, did not inhibit them from going to the other extreme and trying to develop tanks that were large and expensive. In particular, the British Army planned to replace its Vickers Medium with a tank officially designated the A. 6 and commonly known as the Sixteen-tonner. This tank, which was designed by Vickers-Armstrongs in 1927, was a considerable advance on the Vickers Me- dium in having a better layout with a separated engine compartment at the rear of the hull and a three-man turret, and it was capable of up to 48 km/h. But at 14mm the maximum thickness of its armour was not greater than that of the contemporary light tanks and less than that of the Renault FT. What is more, its main armament consisted of a 47mm gun, which was virtually the same as the gun already used for several years in the Vickers Medium. The use of this gun was hardly compensated for by the addition of two small turrets, each with two machine guns, which were incorporated in the Sixteen-tonner at the express request of the Royal Tank Corps.