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date of publication: 28-12-2012

Medium Tank A-20


The Soviet prototype of the was further advanced and stuck closely to ABTU specification. The 18,2 tonne (18 ton) design retained the wheel/track configuration of the BT series. Like its BT forebears, it ran on four pairs of road wheels powered by the new, compact and powerful 373kW (500bhp) V-2 diesel tank engine. The chassis was based on that of the BT-7M. It was armed with the 45mm (1,77 in) high-velocity gun, like most of the BT series, as well a coaxial and hull-mounted machine gun.

The shape of the tank, however, was more interesting, as it provided the first glimpse of the hull and turret shape that would later be adopted in the . The A-20 had a new 25mm (1in) rolled armour plate turret. The A-20's wide, V-shaped glacis plate was set at 60 degrees. The hull overhung the tracks, and the hull sides above track level were angled and 25mm (1in) thick. This conformed to the same specifications of another attempt to produce a shell-proof tank: the T-46-5 (or Izdeliye 111). This 32,3 tonne (32 ton) tank had reached the prototype stage and but was cancelled. However, its armour protection schemes had some influence on the A-20.

The T-34: Medium Tank T-34/76B

The attempt to up-gun the medium tank A-20 in the shape of the A-30 soon proved to be a dead end. The design team made an attempt to place the short-barrelled 76,2mm (3in) (L/30,5) gun used on the BTU in the A-20 turret. This failed comprehensively because the turret was far too small for the larger weapon, making it extremely difficult to operate. More fundamentally, the turret ring could not absorb the recoil of the 76.2mm (3in) gun. Eventually, the basic impracticability of the project ensured that the A-30 was quietly dropped.

The A-32 was a far more promising design and a major development on the BT. The wheel/track system was dropped, although the tank retained the suspension system. As it did not have to move on wheels, the weight saving was considerable, and the amount of armour on the new hull shape could be in creased to 30-60mm (1,2-2,4in) without violating the weight limit. The designers also gave the A-32 a new steering system that used the conventional method of levers, rather than the steering wheel used in the BT and the A-20 tank. They had discovered on the series that while a steering wheel was certainly not the best method of steering a tracked vehicle, it had proved impossible to steer a wheeled vehicle with levers. The road wheels were increased to five. Finally, true to Koshkin's original proposal for a tank with a larger gun as well as thicker armour, it was given a 76,2mm (3in) gun.

Prototypes for both the tank A-20 and A-32 were ready by July 1939 and were sent to the Scientific Test Institute of Tank Technology (NIB) at Kubinka, where they both proved mechanically reliable and superior to all other models. The A-20's performance without tracks was poor bur, like the A-32, with tracks it was very satisfactory. On 1 September 1939 both the A-20 and A-32, along with the KV heavy tank and the expensive and complex , appeared in a display of new vehicles which was held for the Main Military Council.

The T-34: Medium Tank T-34

The inclusion of the two tanks in the display indicated official satisfaction with the design, although there was no consensus amongst the Main Military Council. Koshkin was adamant that the A-32 was the superior model, and reckoned it ought to be considered a universal tank to replace the variety of Soviet types and fulfil the roles of the BT, T-26 light tank and T-28 medium tank. Its disadvantage was that it was comparatively expensive, and some of the council expressed serious concern that the A-32 would cost three times as much as the . Pavlov supported the tank A-20, which was the ultimate product of his initial ABTU design specification.


The issue was finally, settled at a meeting of the Defence Committee of the SNAKE on 19 December 1939. The debate turned to the latest repons from the fighting in Finland, which had been invaded by the USSR in November 1939. The experience appeared somewhat similar to that in Spain and Khalkin Gol, stressing the vulnerability of Soviet tank to the small number of Finnish antitank guns. In addition, their armament - which was usually the standard 45mm (1,77in) or short, low velocity 76,2mm (3in) gun - proved inadequate against emplaced Finnish bunkers.

Koshkin told the committee that, after considering these developments, his team had prepared estimates which demonstrated that the A-32 could be up-armoured even further without an unacceptable loss of performance and mobility. Koshkin produced drawings and to back up his case, and convinced Stalin - who was chairing the committee - to approve the up-armoured version of the A-32 medium tank. In service, this medium tank would replace the BT and T-28.

With the outset of war in Europe in 1939, the committee ordered into production a project that Koshkin emphasized was incomplete: a prototype had not yet been built. Representatives of the Committee for Medium Industry were told that the High Command wanted 200 built in the following year. All that remained now was to give the tank a suitably resounding name.