BT tank The BT tanks ( , lit . " fast tank " ) were a series of Soviet cavalry tank s 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 its diminutive " Betushka " . The direct successor of the BT tanks would be the famous T - 34 medium tank , introduced in 1940 , which would replace all of the Soviet fast tanks , infantry tanks , and medium tanks in service . 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 Winter War in Finland , in the Battle of Khalkhin Gol , the Polish campaign , in the early and last days 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 . Production history . 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 a 37 mm gun and a machine gun , but shortages of 37 mm guns led to some early examples being fitted with three machine guns . The BT - 5 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 cavalry tank s , as well as the T - 28 medium tank . 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 : 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 1939 border skirmishes against Japan ( including the battle of Khalkhin Gol ) , both BT - 5s and BT - 7s were used . Again the BT tank generally outclassed the lightweight enemy tanks . Against Finland during the Winter War , mainly BT - 2 and BT - 5 tanks were less successful . The Finnish forces were well - led , highly motivated and defended very constricted terrain . The thinly - armored BT tanks were very vulnerable to dug - in Finnish anti - tank guns ( especially the 37mm Bofors , but also the 20mm Lahti ) and routinely destroyed as long as there was a gun available in that sector . During the Second World War , BT - 5 and BT - 7 tanks were used in the 1939 Soviet invasion of Poland , and in large numbers in the battles of 1941 - during which many were abandoned or destroyed . A few remained in use in 1942 , but were rare after that time . The Red Army planned to replace the BT tank 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 the invasion of Japanese - occupied Manchuria , during August 1945 . This was the last combat action of BT tanks . Technical legacy . The BT tank series was numerous , forming the cavalry tank arm of the Red Army in the 1930s , 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 tank was the T - 34 medium tank , designed by the same bureau , and drawing many lessons from the fast tanks . Along the way , an important technical development was the BT - IS and BT - SW - 2 testbed vehicles , concentrating on sloped armour . This proof - of - concept led directly to the armour layout of the T - 34 . BT tank chassis were also used as the basis for engineering support vehicles and mobility testbeds . A bridgelayer 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 BT tanks . The KBT - 7 was a thoroughly modern armoured command vehicle that was in the prototype stage when World War II broke out . The design was not pursued during the war . In the Kiev maneuvers of 1936 , foreign military observers were shown hundreds of BT tanks roll 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 Christie suspension designs . Interestingly , the pointed shape of the hull front armor on the BT tank also influenced the design of the British Matilda tank .