History, Development, and Use
of the BT-7 Medium Tank

This section will cover the history, development, and use of the BT-7 medium tank. In this section you will find where the tank has been used, when it was designed, its limitations and abilities, and how the functions.

 

Brief Developmental History

The BT-7 light tank was a further refinement of the BT tank family.  It came about as the result of the Soviet experience in the Far East where they had fought the Japanese in a number of small border clashes in 1934 and 1935.  These clashes showed that the BT-5 had several vulnerabilities that would have to be remedied with a more modern design.

This design would have all welded armor, rather than the vulnerable riveted armor of earlier tanks.  This was because light machine gun fire would often strike the head of the rivets and send fragments of it into the tank with fatal results to the crew.  The armor thickness would also be increased to 22mm in some areas.  A better main gun was fitted to the tank, known as the M-1935 45mm cannon.  The tank would also be able to carry 146 rounds of main gun ammunition, which was 31 more than the earlier BT-5.  

All of these improvements began to increase the weight of the new tank so a new more powerful engine was fitted.  The transmission system of the tank was also strengthened to handle the new stress requirements.  Like its predecessors, the BT-7 would be equipped to run on either wheels or tracks to increase mobility.

Production of the new BT-7 began in 1936.  Soon after production began the turret design would be altered.  A new conical turret would be used which provided more protection from small arms and machine gun fire.  The turret would retain the two hatches found on earlier tanks however.  A further improvement was added to the main gun, which received an electric firing system.  In 1938 the aiming system of the tank was improved.  The BT-7 would now use two panoramic targeting scopes as well at the TOP-30 targeting scope.  

As production continued many smaller improvements were introduced.  Among these were the use of smaller track links which were less prone to sliding in mud and snow.  A new steering system which used a control stick in place of a steering wheel made the tank easier to drive. Some tanks experimented with diesel engines which increased range and reduced fire risk. Other BT-7s during this time would have a ball mounted machine gun installed into the turret rear to keep ward off enemy infantry.  The tank proved to be very popular with its crew members.

Production of the final variants of the BT-7 (known as the BT-7M or BT-8) began in 1939 and ended in early 1941.  They weighed some 14.6 tons and used the W-2 diesel engine which increased top speed and range.  All were armed with the M-1938 model 45mm cannon and had three DT machine guns.  Only about 700 of these tanks were built.

BT-7 Variants

In addition to the basic model, other versions of the BT-7 would see front line service.  The most common of these were the BT-7TU command tank, which differed from the standard tank in that it had a radio and could carry only 132 shells.  Older versions of this tank were equipped with the cylindrical turret and a frame mounted antennae, while later models with the conical turret used a more conventional whip antennae.

A fire support version known as the BT-7A was made in small numbers.  These 'artillery tanks' weighted 14.5 tons and carried a short 76.2mm M1927/36 gun.  Due to their increased weight they operated with their tracks at all times.  The BT-7A could carry 40 shells if they had a radio or 50 shells if they did not.  They vehicle was also equipped with a 7.62 DT machine gun which was located in a separate ball mantlet.  A flamethrower version of the BT-7 known as the OP-7 was also built but few were made and even fewer reached the battlefield.

Combat History

The BT-7 was first used in combat against the Japanese during the battles at Khalkin Gol where they faced very little Japanese armor.  At that battle they enabled General Zhukov's force to conduct a double envelopment of Japanese forces and helped bring a quick end to the conflict.  The BT-7 would then see action again during the Soviet invasion of Poland in 1939.

BT-7 was used against Finland during the Winter War.  During that conflict the tank was unable to make use of its speed and mobility because of Finland's poor road network and cold winter.  Furthermore, despite its increased armor the tank still proved vulnerable to Finnish anti-tank guns.  This led the Soviets to consider developing a more capable tank.

When the German army invaded the Soviet Union in 1941, the BT-7 would see action one final time.  Large numbers of the tanks were sent West in an effort to stop the invading Germans.  In one on one combat the BT-7 proved that it was the equal of the Panzer III, but Soviet tank units were often inexperienced unit commanders who were outmatched by their German counterparts.  Poor crew training and lack of spare parts also worked against the BT-7 tank fleet, and by late 1941 many of the tanks were either destroyed or captured.  In fact, the German army also made use of captured BT-7 tanks, but had to mark them so that they could avoid friendly fire incidents.

   

Tactical Use and Limitations

The BT-7 fast tank was designed to engage front line enemy tanks and make sweeping breakthroughs into enemy rear areas.  Once in the rear areas it was to engage and destroy artillery concentrations, supply trucks, and command posts.  It was only successful in this role against the Japanese during the battles of Khalkin Gol in the late 1930's.

Armor and speed were the BT-7's advantages.  The increased armor and lack of rivets gave the BT-7 greater survivability when compared to the earlier BT's.  It also pioneered the use of sloped armor in its glacis plate, conical turret, and the diesel engine.

Despite its increased armor, the BT-7 was still not 'shell proof' and could be knocked out of action by relatively small anti-tank guns.  The gasoline engine found in most versions of the BT-7 left them vulnerable to fires whenever it was hit.  The later BT-7M's equipped with a diesel engine were to few in number to make any significant impact.

 

Deployment Chronology

The BT-7 fast tank was a product of the rapidly changing technologies of the late 1930's.  It built upon the improvements of earlier designs and paved the way for the legendary T-34.  In this section you can see what vehicles the BT-7 replaced and tanks eventually replaced it.  You will be able to find more about each of these vehicles by clicking on the links below.

The BT-7 replaced... BT-7 Fast Tank The BT-7 was replaced by...
BT-5 Fast Tank T-34/76 Medium Tank

 

Sources Cited

Here are some of the most informative sources that we have used in compiling this information for you.  We hope you can find them as useful as we have.

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