BT tank

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BT-5
BT-5 command tank, with horseshoe antenna around the turret top
Type	Cruiser tank
Place of origin	Soviet Union
Specifications
Weight	11.5 tonnes
Length	5.58 m
Width	2.23 m
Height	2.25 m
Crew	3
Armor	6 to 13 mm
Primary armament	45 mm Model 32
Secondary armament	DT machine gun
Engine	Model M-5 400 hp (298 kW)
Power/weight	35 hp/tonne
Suspension	Christie
Operational range	200 km
Speed	72 km/h

The Fast Tank (Russian: Быстроходный танк, Bystrokhodny tank), was a series of Soviet 'cruiser tanks' which were produced in large numbers between 1932 and 1941. 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 by the diminutive version Beteshka.

[edit] Overview

The BT tanks were 'convertible tanks'. This was a feature designed by J. Walter Christie to reduce wear of the unreliable tank tracks of the 1930s. In about thirty minutes the crew could remove the tracks and engage a chain drive to the rearmost road wheel on each side, allowing the tank to travel at very high speeds on roads. In wheeled mode the tank was steered by pivoting the front road wheels. However, Soviet tank forces soon found the convertible option of little practical use in a country with few paved roads, and it consumed space and added needless complexity and weight. The feature was dropped from later Soviet designs.

BT tanks saw service in the Spanish Civil War, in the Far East, in the Winter War in Finland, the Polish campaign, and in the early part of World War II. The BT tank design served as a platform for experimentation with artillery support tanks and advanced armour layout, and further development led directly to the famous T-34 tank.

[edit] Production history

The BT-2 tank of 1932 was the first Soviet modification of Walter Christie's design.

In 1930, Soviet agents at Amtorg, ostensibly a Soviet trade organization, used their New York political contacts to persuade U.S. military and civilian officials to provide plans and specifications on the Christie tank design to the Soviet Union. At least two of Christie's M1931 tanks (without turrets) were later purchased in the United States and sent to the Soviet Union under false documentation in which they were described as 'agricultural tractors'. Both tanks were successfully delivered to the Kharkov Komintern Locomotive Plant (KhPZ). The original Christie tanks were designated fast tanks by the Soviets, abbreviated BT. Based on the Christie prototypes and previously obtained plans, three unarmed BT-2 prototypes were completed in October 1931 and mass production began in 1932. Most BT-2s were equipped with 37 mm gun and one machine gun, but shortages of 37 mm guns led to some early examples being fitted with three machine guns. The BT-3 and later models were equipped with a 45 mm gun. The sloping front armor design of the Christie M1931 prototype was retained in later Soviet tank hull designs, later adopted for side armor as well.

In 1937, a new design team was formed at the KhPZ under Chief designer Mikhail I. Koshkin, to create the next generation of BT tanks. The team built a BT prototype called the A-20, but also built a more heavily armed and armoured derivative, the A-32, a "universal tank" to replace both the T-26 infantry tank and BT line of cruiser tanks. The design was controversial, but concerns about tank performance under the threat of German Blitzkrieg led to the approval for production of a still more heavily-armoured version, the T-34 medium tank.

Production:

• BT-2: 620
• BT-5: 2,108^[1]
• BT-7: 4,965^[2]
• BT-7M: 790^[3]

[edit] Variants

BT-7A "artillery support tank" was a self-propelled gun variant, armed with a 76.2 mm howitzer.

• BT-1: Christie prototype.
• BT-2 Model 1932: 37 mm gun, M-5 engine (copy of U.S. Liberty engine).
• BT-5: larger cylindrical turret, 45 mm gun, ball-mount MG.
  • BT-5 Model 1933: new turret with twin hatches, larger bustle and coaxial MG.
  • BT-5PKh: snorkelling variant (prototypes only).
  • BT-5A: artillery support version with 76.2 mm howitzer (few made).
  • BT-5 flamethrower tank: (prototypes only).
  • PT-1A: amphibious variant with new hull (few made).
• BT-7 Model 1935: welded hull, redesigned hull front, new Mikulin M-17T engine (copy of BMW), enclosed muffler.
  • BT-7 Model 1937: new turret with sloping armour.
  • BT-7TU: command version, with whip antenna instead of earlier horseshoe antenna.
  • BT-7A: artillery support version with 76.2 mm howitzer.
  • OP-7: flame-thrower version with external fuel panniers.
• BT-7M^[4] (1938, prototypes designated A-8; sometimes referred to as BT-8): new V-2 diesel engine replacing earlier gasoline engines, three DT machine guns: coaxial, in P-40 AA mount on roof and in a ball-mount on turret rear.
• BT-42: Finnish assault gun, captured BT-7s were equipped with British 114 mm howitzers.
• BT-IS: Prototype/proof-of-concept platform with heavily sloped armor; forerunner of the armor design on the T-34.
• BT-SW-2 Cherepakha ("turtle"): Another prototype, which took the armour sloping to an extreme.
• A-20: Prototype for a new BT tank, with 20 mm armour, 45mm gun, model V-2 diesel engine, and 8×6-wheel convertible drive. Lost out in trials to the A-32, which was further improved and produced as the T-34 medium tank.

• TTBT-5, TTBT-7: teletanks, remote-controlled tanks.

[edit] Specifications

BT-5 tanks in the Winter War in Finland.

A BT-7 crewman converses with German troops at the so-called "Border of Peace" set up after the 1939 invasion of Poland under the Molotov-Ribbentrop Pact.

[edit] Combat History

BT tanks were used in combat on several occasions prior to World War II. A battalion of BT-5s saw action on the Republican side in the Spanish Civil War, where their 45 mm guns could easily destroy the opposing German and Italian light tanks. In the border skirmishes against Japan in 1939 (including the battle of Khalkhin Gol), both BT-5s and BT-7s were used. Again the BT generally outclassed the lightweight enemy tanks. Against Finland during the Winter War (mainly BT-2 and BT-5 models) the BT was less successful. The Finnish forces were well-led, highly motivated and defending very constricted terrain. The thinly-armored BTs were very vulnerable to dug-in Finnish anti-tank guns.

In the Second World War, BT-5s and BT-7s took part in the Soviet occupation of eastern Poland in 1939, and in large numbers in the battles of 1941. Most of these tanks were abandoned or destroyed in the disastrous 1941 campaign. A few continued in use in 1942, but they became quite rare after that time.

The Red Army planned to replace the BT series with the T-34 and had just begun doing so when the German invasion (Operation Barbarossa) took place.

In the Far East, a significant number of BT-7 tanks took part in Operation August Storm against Japan in Manchuria, during August 1945. This was the last combat action of BT-series vehicles.

[edit] Technical Legacy

BT-7 tanks on parade.

The BT series was numerous, forming the 'cavalry tank' arm of the pre-war Red Army, and had much better mobility than other contemporary tank designs. For these reasons, there were many experiments and derivatives of the design, mostly conducted at the KhPZ factory in Kharkov, Soviet Ukraine.

The most important legacy of the BT was the T-34 design, derived in part from the BT. The T-34 had many innovations well beyond the BT, but the lineage is obvious. Along the way, an important technical development was the BT-IS and BT-SW-2 series of testbed vehicles, which demonstrated the construction of vehicles with very heavily-sloped armor. This proof-of-concept led directly to the armor layout of the T-34.

BTs were also used as chassis for engineer support vehicles and mobility testbeds. A bridgelayers variant had a T-38 turret and launched a bridge across small gaps. Standard tanks were fitted as fascine carriers. The RBT-5 hosted a pair of large artillery rocket launchers, one on each side of the turret. Several designs for extremely wide tracks, including, oddly, wooden 'snowshoes' were tried on BTs.

The KBT-7 was a thoroughly modern armored command vehicle that was in the prototype stage when WW2 broke out. The design was not pursued during the war.

In the Kiev maneuvers of 1936, foreign military observers were shown hundreds of BTs rolling by a reviewing stand. In the audience were British Army representatives, who returned home to advocate for use of Christie suspension on British cruiser tanks. The British A-13, Crusader, and Cromwell tanks all used suspension designs derived from the Christie via the BT. Interestingly, the pointed shape of the hull front armor on the BT also influenced the design of the British Matilda tank.

[edit] References

1. ^ KMDB - BT-5 Light Wheeled/ Tracked Tank
2. ^ KMDB - BT-7 Light Wheeled/ Tracked Tank
3. ^ KMDB - BT-7M Light Wheeled/ Tracked Tank
4. ^ KMDB - BT-7M Light Wheeled/ Tracked Tank

• Zaloga, Steven J.; James Grandsen (1984). Soviet Tanks and Combat Vehicles of World War Two. London: Arms and Armour Press. ISBN 0-85368-606-8. 

[edit] External links

Wikimedia Commons has media related to:

BT tank

• Tank development index at the Russian Battlefield
• BT tanks and their variants at Henk of Holland
• Salvage of BT-7 tank from Neva river