The penchant for additional machine gun turrets was not confined to the British Army. The French 2C heavy tank already had a second machine gun turret at the rear of the hull and so did the 16 ton Grosstraktoren built secretly in Germany in 1929. The very first Japanese tank built in 1927 went further in having an additional machine gun turret at the front as well as the rear. The 19.5 ton Neubaufahrzeuge built in Germany in 1934 also had two machine gun turrets. But the provision of additional machine gun turrets was carried to an extreme in the A. 1 Independent heavy tank built in Britain in 1926 which had no fewer than four.
The Vickers A1E1 in 1925
This aberration in tank design can be ascribed in part to the influence of naval ideas and the concept of the employment of tanks by themselves, which required them to ward off attacks from all quarters. In part it was also due to the contemporary tendency in Britain to overrate the effectiveness of machine guns and to ignore the need to arm tanks with guns of more than small calibre. This tendency was clearly demonstrated by the main armament of the 32 ton Independent which consisted only of a 47mm gun.
The other multi-turreted tanks, such as the Grosstraktoren and the Neubaufahrzeuge. did at least mount 75 mm guns in their main turrets. Multi-turreted tanks built in the Soviet Union were similarly armed with 76.2mm guns. They included the 17 ton T-2S first built in 1932. which had a machine gun turret on either side of the driver, like the British Sixteen-tonner. and the 45 ton T-32 and T-35, built in 1930 and 1933 respectively, which had five turrets like the Independent.
The 75 or 76.2mm guns mounted in German and Russian multi-turreted tanks were what the tanks of the period should have been armed with in general. Although they were short-barrelled, they fired projectiles which were effective against the armour of the contemporary tanks. At the same time they were of sufficiently large calibre to fire high explosive shells that were effective against various other targets. In consequence, tanks armed with them became what they basically are, namely a mobile source of fire power effective against virtually all battlefield targets. As versatile tank weapons they differed fundamentally from the 93.4mm mortars mounted in the close support versions of the Vickers Medium and other British tanks which were specialised weapons, intended primarily to fire smoke shells and never provided with armour-piercing ammunition.
In the meantime another category of tanks had come to the fore. It consisted of light tanks larger and heavier than those of the Vickers Carden Loyd pattern and armed not only with machine guns but also with 37 to 47mm guns. Unlike the lighter tanks they were capable, therefore, of fighting other contemporary tanks and they were also generally more effective tactically because they had two-man turrets.
Although they were lighter than the contemporary medium tanks but because they were armed with guns of the same calibre as some of the latter, tanks of this kind could be regarded as 'light-medium' rather than light tanks.
The BT, a 'light-medium', which was built in large numbers in the Soviet Union, was the most successful. The BT owed its origin to the outcome of several years' work in the United States by J W Christie on fast tanks which could run on wheels as well as tracks, an idea explored in several different forms during the 1920s. The most notable outcome of this work was an experimental vehicle built by Christie in 1928 which attained what was then a record speed of 68 km/h. A small number of T3 and T4 tanks was built from its basis between 1931 and 1936 for the U. S. Army, which did not however develop them any further. But in 1930 Christie sold two chassis to the Soviet Union, where they served as the basis for the design of the BT, which began to be produced by the end of 1931.
Of the major features which the BT inherited from Christie, the ability to run on the road wheels after the removal of the tracks proved of little value. But the BT very successfully followed Christie's ideas in having large, independently sprung road wheels and a high power-to-weight ratio. In 1933 the Russians added to this a 45mm gun and the BT became what was probably the most effective tank of the mid-1930s.
Six years after the Russians adopted Christie's ideas the British Army took note of what they had achieved with the BT and decided to use his type of suspension for British tanks. In the meantime, the A. 6 Sixteen Tonner and the Mark III Medium derived from it had been abandoned as too expensive and an attempt to produce a cheap medium tank with three turrets, the A. 9, did not prove a success. The next tank to be designed, in 1934, the A. 10 was much more sensible as it dispensed with the additional machine gun turrets. What is more, its original, A. 10 E. 1 version introduced what was to become many years later the standard configuration of tanks, with only the driver at the front, a three-man turret in the centre and the engine and transmission compartment at the rear of the hull. This configuration was then combined with a Christie-type suspension to produce in 1938 a new tank, the A. 13.
The A. 13 was somewhat larger than the BT but it was superior to it in having a three-man turret and short-pitch tracks, instead of Christie's noisy long-pitch tracks with which the Russians persevered. It also dispensed with Christie's idea that tanks should be able to run on their road wheels without tracks as well as with them, which was rightly adjudged in Britain to be an unjustified complication. Otherwise the general characteristics of the two tanks were similar, which included their weight of 13.8 to 14 tons. Thus A. 13 had the makings of a highly mobile, light-medium tank that could be used effectively in a number of roles. Unfortunately it was not regarded as such but as a more specialised 'cruiser' tank intended to be used in the cavalry role to which British armoured formations were being confined.
What is more, those in charge of British tank development still hankered after multi-turreted tanks and in 1938 placed orders for the A. 14 and A. 16 'heavy cruisers'. Each of these, once again, had two additional machine gun turrets but neither mounted in its main turret a gun larger than that of the A. 13. Development of the A. 14 and A. 16 was mercifully abandoned in 1939 but the tank which followed the A. 13 cruisers, the A. 15 or Cruiser Tank Mark VI, Crusader, still had one additional machine gun turret and the same 40mm gun as the A. 13.