BT-7M, 1940, with tracks removed from the wheels and carried on the hull
|Type||Light cavalry tank|
|Place of origin||Soviet Union|
|Wars||Soviet–Japanese Border Wars, World War II, Winter War|
|Number built||2700 - 5300|
|Variants||BT-7-1, BT-7-1V, BT-7-2, BT-7A, BT-7M (BT-8), BT-IS|
|Specifications (variant BT-7-2)|
|Weight||13.9 tonnes (13.7 long tons; 15.3 short tons)|
|Length||5.66 m (18 ft 7 in)|
|Width||2.29 m (7 ft 6 in)|
|Height||2.42 m (7 ft 11 in)|
|Armour||Hull: 6-20 mm
Turret: 10-15 mm
|45 mm L/46|
|2 x 7.62 mm DT machine gun|
|Engine||Mikulin M-17T (V-12) gasoline
450 hp (at 1,750 rpm)
|Transmission||Chain drive (tracks: sliding gear)|
|Ground clearance||0.305 m (1 ft)|
|Fuel capacity||360 litres (95 US gal)|
|Road: 430 km (270 mi)
Off-road: 360 km (220 mi)
|Speed||Road: 72 km/h (45 mph)
Off-road: 50 km/h (31 mph)
The BT-7 [note 1] was the last of the BT series of Soviet cavalry tanks that were produced in large numbers between 1935 and 1940. They were lightly armoured, but reasonably well-armed for their time, and had much better mobility than other contemporary tank designs. The BT tanks were known by the nickname Betka from the acronym, or its diminutive Betushka.
The first prototypes of the BT-7 had a distinctive canted-ellipse shaped turret mounting both the main gun and a coaxial machine-gun. The specification also called for the project to allow for installation without any significant change to the framework of new guns: the 76 mm KT-26 or PS-3 main gun (a short-barreled howitzer) and the 45 mm 20K model 1932/38, a long-barreled, high-velocity gun useful against tanks, but less effective than the 76 mm gun against infantry.
In the rear of the turret there was housed a rotating drum-type magazine for 18 45 mm shells or a radio station. The prototype underwent an extensive testing program in the summer and autumn of 1934. As a result of this testing, it was felt that a machine-gun was unnecessary on a tank with a 3-man crew, especially as it made the assembly of the turret more complicated.
Therefore, in early 1935, the tank went into production with a simpler design, incorporating the turret from the BT-5. (However, the idea of wheeled/tracked vehicle with a 76 mm cannon was not abandoned and the plant was commissioned to develop a new BT-7 turret from the turret of the T-26-4.) In the production model, a cylindrical turret housed a 45 mm 20K gun with a DT-model machine-gun. On some of the tanks, a model 71-TC radio with frame antenna was installed.
The crew consisted of three men: the commander (who also served as the gunner); the loader and the driver. In 1937 the company launched production of the BT-7 with a conical turret. Main armament remained the same, but the ammunition was increased to 44 rounds. All serving tanks now installed the DT machine gun in the rear niche. For the firing of the gun and coaxial machine gun at night, the tank was equipped with two special projector-type headlamps, and a mask placed on the gun. Subsequently, these lights were retrofitted to earlier models of the tank. Improvements were also made to the drive wheels, caterpillar tracks and gearbox by 1938.
In parallel with the main modification, 154 BT-7A artillery tanks were produced between 1936 and 1938, fitted with a larger turret and a 76 mm KT-type gun, 50 rounds of ammunition (40 in a tank with a portable radio).
In 1938, four experimental BT-8 tanks mounted with V-2 diesel engines were produced. After comparative tests of the BT-7 and BT-8, the diesel tanks were put into production in 1940 (under the designation BT-7M) with the powerplants being produced in a separate plant of the Voroshilovets factory to ensure supply. From December 1939, the BT-7A went into production with some minor modifications - additional bracing for rigidity, a manhole underneath, and a smaller air filter. The diesel tanks showed much-reduced fuel costs, and the petrol-powered tanks were soon placed into reserve.
Several experimental tanks were conceived based on the BT series, for example the wheeled BT-IS, designed by N.F. Tsyganov, a platoon commander in the 4th Armoured Regiment of the Ukraine Military District and self-taught designer. The type successfully passed field tests but was not ordered in bulk. Another Tsyganov design was the S-2 "Cherepaha" (turtle, черепаха), with a new design of hull and turret. There was also the command tank KBT-7 with a fixed turret, the OT-7 mounting a flamethrower, the KhBT-7 designed to protect from toxic contamination and lay smokescreens, the SBT bridgelayer and the TTBT-7 and Thubten-7 radio-controlled tanks (known at the time as Teletanks). Finland converted 18 captured tanks into BT-42 assault guns.
Shortly before Operation Barbarossa, the BT-7 underwent an up-armour programme. In 1940, Mariupol Ilyich Iron and Steel Works produced 50 sets of hinged homogeneous armor for the BT-7M, which increased the weight of the test tank to 18 tons. On the installation of these kits to military units, unfortunately, nothing is known. Between 1935 and 1940, between 2700 and 5,328 BT-7 tanks of all modifications (except BT-7A) were built.
In June, 1941, at the outset of the German invasion of the Soviet Union, the BT-7 was the main battle tank of the Soviet army. Tank losses were high, with over 2000 BT-7 series tanks lost in the first 12 months on the Eastern Front. Hundreds more had been immobilized before the invasion by poor maintenance, and these had to be abandoned as the Soviet forces withdrew eastward. Still, the BT-7 continued to be produced. The BT-7 continued to be operated by the armored and mechanized forces of the Red Army for almost the entire war.
The BT-7 series continued in use by the Russians in the east, where Japanese forces lacked the heavy tanks of their German allies. The BT-7 was employed in Soviet operations against Japanese held territories in the Battle of Khalkhyn Gol and the Manchurian Strategic Offensive Operation in Manchuria in 1945.
Organization and use
The Table of Organization and Equipment for a typical Soviet light tank brigade in 1939 is as follows:[clarification needed]
- 3 tank battalions, each containing
- 1 reserve tank company, with 8 BT-7 or T-26 tanks;
- 1 signal company, with 5 T-37 tanks;
- 1 motorized infantry battalion, containing
- 3 motorized rifle companies;
- 1 signal platoon;
- 1 antitank platoon with 3 45 mm antitank guns;
- 1 AA MG platoon
- 1 additional AA MG platoon in brigade headquarters;
- 1 motor transport battalion;
- 1 reconnaissance battalion;
- 1 pioneer company;
- 1 medical company;
- 1 chemical company.
- BT (Russian: БТ) is the Russian abbreviation for "fast tank" (Быстроходный танк, Bystrokhodny tank).
- "Russia's BT-7 Fast Tanks" at wwiivehicles.com. URL accessed 2006-07-25.
- Zaloga 1984, p 74.