Generally speaking, the Soviets followed a gradual approach in tank design, modifying a proven design rather than starting from scratch.
The Soviet Union produced a large number of tank designs in the period between the two world wars. Early Russian experiments with AFVs in World War I had been limited to armored cars, such as the Austin Putilov. Based on a British chassis, it had entered service early in World War I. Lacking the industrial base of the other major military powers, the Russians concentrated in the postwar period on light tanks of simple design. Their first tanks were a few British and French models captured by the Bolshevik forces (known as the Reds) from their opponents (the Whites) during the Russian Civil War. The first Russian-built tank appeared in August 1920. It weighed some 15,700 pounds and had armor up to 16mm thick.
With no tank design experience of their own, the Russians came to rely on the Germans in this regard. The new Bolshevik government of Russia and Weimar Germany found themselves at odds with the Western powers after World War I, and in 1922 at Rapallo the two governments normalized relations. Following this the two states undertook a clandestine military collaboration that included a German- Soviet tank-testing facility at Kazan in the Soviet Union. This gave the Germans an opportunity to carry out tank development in violation of the Versailles treaty, and the Soviets gained access to German technological and design developments.
Although its designers had their own plans, the Soviet Union, in order to take advantage of new developments abroad, purchased a number of prototype tanks from other countries, including the Vickers tanks from Britain and Christie designs from the United States. The Vickers 6-Ton was the license-built Soviet T-26A. The T-26 of 1931 appeared in A and B versions. The A version, designed for infantry support, had twin turrets. The first production model mounted one 7.62mm machine gun in each turret. A follow-on mounted first a 27mm gun and then a 37mm gun in the right turret. The T-26A weighed some 19,000 pounds and had a crew of three. Powered by an 88-hp gasoline engine, it had a maximum speed of 22 mph. It had maximum 15mm armor protection.
The single-turret T-26B version was intended as a mechanized cavalry AFV and mounted a high-velocity gun. The initial model mounted a single 37mm gun; follow-on models mounted a 45mm main gun. Despite their obsolescence, Soviet T-26 tanks fought in the early battles on the Eastern Front during World War II.
The Soviet Union also purchased the light Vickers/Carden-Loyd tankette that the British abandoned. The Soviets enlarged it and put it into production in 1934. Some 1,200 were made as the T-37 light amphibious reconnaissance tank. The T-37 employed the Vickers hull and suspension married to a turret of Soviet design. A small propeller at the rear of the tank pushed it through water. Weighing some 7,100 pounds and capable of being air-lifted beneath a bomber, it had a 40-hp engine and could reach 21 mph on the road. It mounted a single 7.62mm machine gun and had only 10mm armor.
An improved T-37 appeared in the T-38, produced beginning in 1936. Basically the T-37 in terms of armament and armor, it had an improved engine, transmission, and suspension. The T-38 remained in service until 1942.
The final tank in this immediate series of light amphibians was the T-40. Quite different in appearance from its predecessors, the T- 40’s hull incorporated buoyancy tanks and had an upswept bow front similar to the later PT-76. It also had a small, sloped turret and was propelled in water by means of a small propeller. The T-40S version was simply a light tank without the amphibian feature. The T- 40 weighed some 12,300 pounds and had a two-man crew. It was armed with two machine guns, or a 20mm cannon and one machine gun. It had an 85-hp engine and was capable of 38 mph. The T-40 influenced the later T-60 and T-70 light tanks, the latter serving into the Cold War.
The U.S. Christie designs and French tanks introduced a sprung bogie suspension system in place of a rigid system. This enabled increased speed without sacrificing armor or requiring an increase in the size of the power plant. This appealed to Soviet designers, and they copied the Christie M-1931 in their BT series of fast tanks (“BT” standing for bystrochodny tankovy, literally “fast tank”). The Soviet BT-1 was an exact reproduction of the Christie. The BT-1 weighed some 20,000 pounds, had a crew of three, and had top speeds of 65 mph on wheels and 40 mph on tracks. It mounted two machine guns and had maximum 13mm armor protection.
Soon the Soviet Union was producing large numbers of BT tanks. The follow-on BT-2 was essentially the same hull as the BT-1 but with a new turret and a 37mm main gun and one machine gun. It was still in service in World War II. The BT-3, introduced in 1934, was essentially the BT-2 but with solid-disk road wheels instead of spoked wheels and a 45mm main gun instead of the 37mm.
The BT-5 incorporated a number of improvements, chiefly in its lightweight 350-hp gasoline engine, originally an aircraft design. Entering production in 1935, the tank itself weighed some 25,300 pounds, had a crew of three, maximum 13mm armor, and could reach 40 mph on tracks. The BT-5 was armed with a 45mm main gun and one machine gun. It formed the basis of Soviet armored formations of the late 1930s. It was in fact superior in almost all performance characteristics to the German PzKpfw I, which mounted only two machine guns. The two tanks came up against one another in the Spanish Civil War of 1936–1939.
The follow-on BT-7 of 1937 was essentially an improved BT-5 incorporating sloped armor. The BT-7 was heavier and slower than the BT-5, reflecting the race between guns and armor and increasing concern about the lethality of antitank guns. Weighing some 30,600 pounds and crewed by three men, it utilized a new engine and had increased fuel capacity. Its two-man turret continued the 45mm main-gun armament. Armor thickness was a maximum 22mm.
