T - 26 The T - 26 tank was a Soviet light infantry tank used during many conflicts of the 1930s and in World War II . It was a development of the British Vickers 6 - Ton tank and was one of the most successful tank designs of the 1930s until its light armour became vulnerable to newer anti - tank guns . It was produced in greater numbers than any other tank of the period , with more than 11 , 000 manufactured . During the 1930s , the USSR developed 53 variants of the T - 26 , including flame - throwing tanks , combat engineer vehicles , remotely controlled tanks , self - propelled guns , artillery tractors , and armoured carriers . Twenty - three of these were series - produced , others were experimental models . The T - 26 together with the BT was the main tank of the Red Army ' s armoured forces during the interwar period . The T - 26 was the most important tank of the Spanish Civil War and played a significant role during the Battle of Lake Khasan in 1938 as well as in the Winter War in 1939 – 40 . Though nearly obsolete by the beginning of World War II , the T - 26 was the most numerous tank in the Red Army ' s armoured force during the German invasion of the Soviet Union in June 1941 . The T - 26 fought the Germans and their allies during the Battle of Moscow in 1941 – 42 , the Battle of Stalingrad and the Battle of the Caucasus in 1942 – 1943 ; some tank units of the Leningrad Front used their T - 26s until 1944 . Soviet T - 26 light tanks last saw use in August 1945 , during the defeat of the Japanese Kwantung Army in Manchuria . The T - 26 was exported and used extensively by Spain , China and Turkey . Captured T - 26s were used by the Finnish , German , Romanian and Hungarian armies . The tank was reliable and simple to maintain , and its design was continually modernised between 1931 and 1941 . No new models of the T - 26 were developed after 1940 . British origin . The T - 26 was a Soviet development of the British Vickers 6 - Ton ( Vickers Mk . E ) ( the Polish 7TP tank was another development of Vickers E 6 - Ton ) tank , which was designed by the Vickers - Armstrongs company in 1928 – 29 . The simple and easy - to - maintain Vickers 6 - Ton was intended for export to less technically advanced countries : the Soviet Union , Poland , Brazil , Argentina , Japan , Thailand , China , and many others . Vickers advertised the tank in military publications , and both the Soviet Union and Poland expressed interest in the Vickers design . In early 1930 , the Soviet buying committee , under the direction of Semyon Ginzburg , arrived in Great Britain to select tanks , tractors , and cars for use in the Red Army . The Vickers 6 - Ton was among four models of tanks selected by Soviet representatives during their visit to Vickers - Armstrongs . Under the contract signed on 28 May 1930 , the company delivered to the USSR 15 twin - turreted Vickers Mk . E ( Type A , armed with two . 303 calibre ( 7 . 71 mm ) water - cooled Vickers machine gun s ) tanks together with full technical documentation to enable series production of the tank in the USSR . The ability of the two turrets of the Type A to turn independently made it possible to fire to both the left and right at once , which was considered advantageous for breakthroughs of field entrenchments . Several Soviet engineers participated in assembly of the tanks at the Vickers Factory in 1930 . The first four Vickers 6 - Ton tanks arrived in the USSR at the end of 1930 . The last tanks arrived in 1932 , when series production of the T - 26 was already in progress . The British tanks were sent to Soviet factories for study in preparation for series production and to military educational institutions and training units . Later , some tanks were given to military supply depots and proving grounds . The Vickers - built 6 - Ton tanks had the designator V - 26 in the USSR . Three British tanks were successfully tested for cross - country ability at the small proving ground near Moscow on Poklonnaya Hill in January 1931 . Kliment Voroshilov ordered the creation of the " Special Commission for the Red Army ( RKKA ) new tanks " under the direction of S . Ginzburg to define the tank type suitable for the Red Army . The T - 19 8 - ton light infantry tank , developed by S . Ginzburg under that programme at the " Bolshevik " Plant in Leningrad , was a competitor to the British Vickers 6 - Ton . The first prototype of the complex and expensive T - 19 was finished in August 1931 . Because both tanks had advantages and disadvantages , S . Ginzburg suggested developing a more powerful , hybrid tank ( the so - called " improved " T - 19 ) with the hull , home - developed engine and armament from the native T - 19 , and the transmission and chassis from the British Vickers 6 - Ton . On 26 January 1931 , I . Khalepsky ( Head of the Department of Mechanisation and Motorisation of the RKKA ) wrote a letter to S . Ginzburg with information obtained via the intelligence service that the Polish government had decided to purchase Vickers 6 - Ton light infantry tanks as well as Christie M1931 cavalry tanks and to mass - produce them with the assistance of both the British and French . Because Poland was then considered , in Soviet military doctrine , to be the USSR ' s main enemy , the Soviet Revolutionary Military Council decided to pass the foreign tanks into Red Army service , starting their production immediately without waiting for completion of development works , in order to counter possible aggression . At that time , the RKKA had only several dozen outdated Mk . V , Mk . A and Renault FT - 17 tanks , captured during the Russian Civil War , together with various armoured cars and obsolescent domestic MS - 1 ( T - 18 ) light infantry tanks . On 13 February 1931 , the Vickers 6 - Ton light infantry tank , under the designator T - 26 , officially entered service in the Red Army as the " main tank for close support of combined arms units and tank units of High Command Reserve " . One of the Vickers 6 - Ton tanks ( equipped with Soviet - made turrets for the pilot batch of T - 26 tanks ) was tested for gunfire resistance in August 1931 . The hull was subjected to rifle and Maxim machine gun fire with the use of normal and armour - piercing bullets at a range of . It was found that the armour withstood gunfire with minimal damage ( only some rivets were damaged ) . Chemical analysis showed that the front armour plates were made from high - quality cemented armour ( S . t . a Plat according to Vickers - Armstrongs classification ) , whereas the homogeneous roof and bottom armour plates were made from mediocre steel . Even so , the British armour was better than armour produced by Izhora Factory for the first T - 26s because of a shortage of modern metallurgical equipment in the USSR at that time . At the same time , the Faculty of Mechanisation and Motorisation of the Military Technical Academy named after F . E . Dzerzhinsky developed two tank models ( TMM - 1 and TMM - 2 ) based on the Vickers 6 - Ton tank design but with an American Hercules six - cylinder water - cooled engine , improved front armour ( to 15 – 20 mm ) , and a driver ' s position on the left side . TMM stands for " tank maloy moshchnosti " or " tank of low power " . The TMM - 1 was equipped with transmission details from the native ( english ) and a ball mount for the DT tank machine gun in front of the hull , whereas the TMM - 2 was equipped with an improved gear box , a steering device without clutches and a 37 mm Hotchkiss gun in the right turret . Representatives from the main Soviet tank manufacturers together with officials from the RKKA Mobilization Department considered the Hercules engine to be too difficult to produce , and the engine tended to overheat inside the engine compartment . Tests of TMM - 1 and TMM - 2 prototypes performed in the beginning of 1932 demonstrated no advantage over the Vickers 6 - Ton and the T - 26 ( the TMM - 2 ' s maneuverability was found to be even worse ) . Design . The Soviets did not simply replicate the Vickers 6 - Ton . Like its British counterpart , the T - 26 mod . 1931 had a twin - turreted configuration and was designed to carry two machine guns , mounting one in each turret . A major difference between the Soviet T - 26 mod . 1931 and the British 6 - Ton were higher turrets on the T - 26 , with an observation slit . Soviet turrets had a round firing port for the DT tank machine gun , as opposed to the rectangular ports used by the original British design for the Vickers machine gun . The front part of the hull was also slightly modified . Hulls of twin - turreted T - 26s were assembled using armoured plates riveted to a frame from metal angles . Some tanks , produced in 1931 , had sealing zinc shims at the hull bottom between armoured plates for fording water obstacles . After problems with rain entering the engine compartment , a special cover was installed over an air outlet window after March 1932 . Some T - 26s produced at the end of 1932 – 1933 had a riveted and welded hull . The T - 26 mod . 1931 had two cylindrical turrets mounted on ball bearings ; each turret turned independently through 240° . Both turrets could provide common fire in front and rear arcs of fire ( 100° each ) . The disadvantage of such configuration was that all the tank ' s firepower could not be used at once on the same side . Four modifications of turrets existed , and they were mounted on tanks in different combinations ( for instance , a tank with a riveted hull could have riveted and welded turrets ) . The hull and turrets of the T - 26 mod . 1931 had a maximum armour thickness of 13 – 15 mm ( until 1938 , see below ) , which was sufficient to withstand light machine gun fire . Many twin - turreted tanks of the first series had 10 mm armour plates of low quality , which could be penetrated by 7 . 62 mm armour - piercing bullets from 150 m . In 1933 , the Soviets unveiled the T - 26 mod . 1933 . The Model 1933 , with a new single cylindrical turret carrying one 45 mm cannon and one 7 . 62 mm machine gun , became the most common T - 26 variant . The 45 mm 20K tank gun was based on the Soviet 45 mm anti - tank gun 19K ( mod . 1932 ) . The T - 26 could carry up to three secondary DT 7 . 62 mm machine guns in coaxial , rear , and anti - aircraft mounts . This increased firepower was intended to aid crews in defeating dedicated anti - tank teams , as the original machine gun armament had been found insufficient . The turret rear ball mounting for the additional DT tank machine gun was installed on the T - 26 tanks from the end of 1935 until 1939 . The T - 26 Model 1933 carried 122 rounds of 45 mm ammunition , firing armour - piercing 45 mm rounds with a muzzle velocity of , or lower - velocity high - explosive munitions . Tanks intended for company commanders were equipped with a radio set and a hand - rail radio antenna on the turret ( so called radio tanks ) . Later the hand - rail antenna was replaced with a buggy - whip antenna , because experience in the Spanish Civil War and Battle of Lake Khasan showed that the hand - rail antenna drew fire onto commander tanks . The tank was powered by a T - 26 flat row 4 - cylinder air - cooled petrol engine which was a complete Soviet copy of the Armstrong Siddeley engine used in the Vickers 6 - Ton . The engine was located in the rear part of the hull . Early Soviet - made tank engines were of bad quality but they became better beginning in 1934 . The T - 26 ( Armstrong Siddeley ) engine did not have an over - speed limiter , which often resulted in overheating and engine valve breakage , especially in summer . A fuel tank for and an oil box for were placed alongside the engine . The engine required top - grade petrol ; the use of second - rate petrol could cause damage to the valve units because of engine detonation . From mid - 1932 , a more capacious fuel tank ( 290 L instead of 182 L ) and a simplified oil box were introduced . An engine cooling fan was mounted over the engine in a special shroud . From early 1932 , the exhaust silencer was affixed by three clamps instead of two . The transmission of the T - 26 consisted of single - disc main dry clutch , a gearbox with five gears in the front part of the vehicle , steering clutches , final drives and band brake s . The gearbox was connected to the engine by a drive shaft passing through the vehicle . A gear change lever was mounted directly on the gearbox . A tank suspension ( for each side ) consisted of two bogies , four rubber - covered return rollers , a track driving wheel and a track idler . Each bogie consisted of a cast box , four twin rubber - covered road wheels connected by balancing levers and two one - quarter elliptic leaf springs . The cast track driving wheel with removable sprocket ring was located in front , and the track idler with a crank lever tightener was located in the rear part of the vehicle . A track made from chrome - nickel steel was wide and consisted of 108 – 109 links . The T - 26 mod . 1931 did not have a radio set . The tank commander communicated with the driver by speaking tube , which was replaced with a signalling lamp in 1932 . The T - 26 was equipped with one fire extinguisher , a kit of spare parts tools and accessories ( including a tank jack ) , a canvas stowage , and a tow chain fixed on the rear of the hull . The T - 26 could cross 0 . 75 m high vertical obstacles and 2 . 1 m wide trenches , ford 0 . 8 m deep water obstacles , cut 33 cm thick trees and climb 40° gradients . It was easy to drive . Beginning in 1937 , there was an effort to equip many tanks with a second machine gun in the rear of the turret and an anti - aircraft machine gun on top of it , as well as the addition of two searchlights above the gun for night gunnery , a new VKU - 3 command system , and a TPU - 3 intercom . Some tanks had a vertically stabilised TOP - 1 gun telescopic sight . Ammunition stowage for the main gun was improved from 122 rounds to 147 . In 1938 , the cylindrical turret was replaced with a conical turret , with the same 45 mm model 1934 gun . Some T - 26s mod . 1938 / 1939 , equipped with radio set , had a PTK commander ' s panoramic sight . In 1938 , the T - 26 was upgraded to the model 1938 version which had a new conical turret with better anti - bullet resistance but the same welded hull as the T - 26 mod . 1933 produced in 1935 – 1936 . This proved insufficient in the Battle of Lake Khasan in 1938 , so the tank was upgraded once more in February 1939 to have an underturret box with sloped ( 23° ) 20 mm side armoured plates . The turret featured an increase to 20 mm at 18 degrees sloping . This time it was designated T - 26 - 1 ( known as the T - 26 mod . 1939 in modern sources ) . There were subsequent attempts to thicken the front plate , but T - 26 production soon ended in favour of other designs , such as the T - 34 . Series production . The beginning . In 1931 , the only Soviet factory suitable for T - 26 production was the " Bolshevik " Factory in Leningrad , which had had experience manufacturing the MS - 1 ( T - 18 ) light tanks since 1927 . It was also planned to use the Stalingrad Tractor Factory which was under construction at that time . But the production of the T - 26 proved to be much more complicated than the semi - handicraft assembly of the MS - 1 , so the planned production of 500 T - 26s in 1931 proved to be impossible . The " Bolshevik " Factory needed to convert all tank drawings from imperial units into metric , in order to develop a production technology , special tools , and equipment . The first 10 T - 26s were assembled in July 1931 – they were identical to British Vickers 6 - Ton tanks except for their armament . Soviet tanks were armed with the 37 mm Hotchkiss ( PS - 1 ) gun in the right turret and the 7 . 62 mm DT tank machine gun in the left turret . These T - 26s from the development batch were of low quality and made from mild steel , but it was an important test of the new tank production technology . The series production of the T - 26 , equipped with new higher turrets with observation window , began in August 1931 . Such turrets proved to be more suitable for mass production . The production of the T - 26 encountered many problems : a lot of armoured hulls and turrets supplied by the Izhora Factory were of low quality ( with cracks ) and were 10 mm thick instead of the planned 13 mm . Poor production standards were the reason behind the frequent failures of tank engines , gear boxes , springs in suspension , tracks and rubber - covered road wheels of early T - 26s . Thirty - five of the 100 T - 26s produced by the " Bolshevik " Factory in 1931 had hulls and turrets made from mild steel . Later , it was planned to replace these hulls with ones built of armour plate as well as to mount engines of better quality . The business plan for 1932 called for 3 , 000 T - 26s . For this , the tank workshop of the " Bolshevik " Factory was reorganised into the Factory No . 174 named after K . E . Voroshilov in February 1932 . The director of the tank factory became K . Sirken and the chief engineer was S . Ginzburg . The problems with organizing the complicated new technological processes , poor production planning of parts suppliers , a great shortage of qualified engineers and technicians as well as of necessary equipment still resulted in many of the tanks being flawed , and they were not accepted by army representatives . On 26 October 1932 , the Trust of Special Machine Industry , consisting of four factories , was established to solve the problem of tank production in the USSR . The planned production of T - 26s for 1932 was decreased significantly and special attention was given to increasing the quality of the tanks . A production run of the new model single - turreted T - 26 armed with the 45 mm gun was launched in mid - 1933 . The Factory No . 174 also manufactured a few T - 26s for military educational institutions . These were dissected tanks to demonstrate the relative position and function of tank components during training of tank crew . Production in Stalingrad . The Stalingrad Tractor Factory ( STZ ) was considered as one of the factories for production of the T - 26 from 1932 , but production in Stalingrad did not start until August 1933 . This process went very slowly , with great difficulties because of delays with deliveries of machining equipment and press tools for the newly built factory . In 1936 – 1939 the Design Office of the STZ developed several experimental tanks ( 6 TK , 4 TG , STZ - 25 , STZ - 35 ) based on the T - 26 tank and the STZ - 5 transport tractor . For instance , the STZ - 25 ( T - 25 ) had the turret , rear part of the hull , engine and some transmission details from the T - 26 mod . 1938 , but the STZ - 25 wheeled - tracked tank weighed and had 16 – 24 mm sloped armour . Factory managers tried to promote tanks of their own design rather than producing T - 26s . As a result , the STZ failed to organise the series production of the T - 26 , but this experience helped to bring the T - 34 into production in Stalingrad in 1941 . The T - 26s produced by STZ had no visual differences from other T - 26s , but Stalingrad tanks were less reliable and more expensive . Modernization and repair . Some early T - 26 tanks were repaired in tank units or factories with the use of later production parts . This meant replacing the all - rubber road wheels ( except the front wheels ) and track idlers with new strengthened ones . Armour was added for the headlight , the armour thickness of the driver ' s hatch lower door of the twin - turreted tanks was increased from 6 to 10 mm and armoured PT - 1 or PTK observation devices were installed . A common hatch above the engine , oil tank , and fuel tank was mounted starting in May 1940 . In 1940 , 255 T - 26s were modernised in this way and in the first half of 1941 another 85 tanks were improved . A central factory responsible for the T - 26 ' s repair and modernisation was the Factory of Carrying - and - Conveying Machines named after S . Kirov in Leningrad , and the Factory No . 105 named after L . Kaganovich in Khabarovsk from the beginning of the Great Patriotic War until 1945 . Production in 1941 . The Factory No . 174 produced its last T - 26 tanks in February 1941 . After that , the factory began retooling to produce the new and much more complex T - 50 light tank . This work was slowed by delays in the delivery of new equipment and series production of the T - 50 did not begin on schedule ( planned for 1 June 1941 ) . As a result , factory management decided to resume the production of the T - 26 , using T - 26 hulls , turrets , and other parts already in stock . About 47 T - 26 tanks were assembled and 77 were repaired in July – August 1941 before the factory was relocated from Leningrad to Chelyabinsk in the end of August 1941 , and then to Chkalov in September 1941 . The Factory No . 174 produced engines and spare parts for the T - 26 , installed additional armour plates on some T - 26s , replaced flame - throwers with 45 mm tank guns in turrets of 130 KhT - 133 flame - throwing tanks , repaired tanks in army units ( 846 T - 26s since the beginning of 1941 ) and mounted about 75 turrets from the T - 26 and the T - 50 as bunkers for the defence of Leningrad . Combat history . The T - 26 entered active service for the Red Army ( RKKA ) in 1932 ; it was used in many conflicts of 1930s as well as during World War II . The T - 26 together with the BT was the main tank of the RKKA armoured forces during the interwar period . The T - 26 light tank first saw action in the Spanish Civil War . The Soviet Union provided Republican Spain with a total of 281 T - 26 mod . 1933 tanks starting in October 1936 . T - 26s were used in almost all military operations of the Spanish Civil War in 1936 – 1939 against Nationalists and demonstrated superiority over the German Panzer I light tanks and Italian CV - 33 tankettes armed only with machine guns . During the battle of Guadalajara T - 26s outclassed the Italian tankettes , inspiring the design of the first Italian medium tank , the Fiat M13 / 40 . The next military operation the T - 26 light tank participated in was the Soviet - Japanese border conflict . Commencing with the Battle of Lake Khasan , in July 1938 . The 2nd Mechanised Brigade , the 32nd and the 40th Independent Tank Battalions had 257 T - 26s , from which 76 tanks were damaged and 9 burnt towards the end of battle action . A small number of T - 26 tanks and flame - throwing tanks based on the T - 26 chassis participated in the Battle of Khalkhin Gol against Japanese forces in 1939 . The T - 26 was vulnerable to Japanese tank - killing teams armed with Molotov cocktail s ; poor quality welds left gaps in the armour plate , and flaming petrol easily seeped into the fighting compartment and engine compartment . The 37 mm gun on the Japanese Type 95 light tank , despite its mediocre performance , was also effective against the T - 26 . Portions of the armour plating on earlier models of the T - 26 used riveted construction and were very vulnerable to both types of attacks . The use of riveted armour on some older T - 26 models led to " spalling " , when the impact of enemy shells , even if they failed to disable the tank or kill the crew on their own , caused the rivets to break off and become projectiles inside the tank . On the eve of World War II , T - 26s served mainly in separate light tank brigades ( each brigade had 256 – 267 T - 26s ) and in separate tank battalions of rifle divisions ( one company of T - 26s consisted of 10 – 15 tanks ) . This was the type of tank units that participated in the Soviet invasion of Poland in September 1939 and in the Winter War of December 1939 – March 1940 . The Winter War proved that the T - 26 was obsolete and its design reserve was totally depleted . Finnish 37 mm antitank guns and even 20 mm antitank rifles easily penetrated the T - 26 ' s thin anti - bullet armour , and tank units equipped with the T - 26 suffered significant losses during the breakthrough of the Mannerheim Line , in which the flame - throwing tanks based on the T - 26 chassis played a significant role . By mid - 1941 , most of the Red Army ' s vast numbers of tanks were suffering from serious wear and tear . Poor quality roads , the vulnerabilities of track design in the early 1930s , and inadequate maintenance , recovery and repair services all took their toll . In some of the front line armoured units , up to half of the T - 26 , T - 28 and BT tanks had major drive train components ( engine , drive train or suspension ) which were broken down or completely worn out , and these disabled tanks were parked and cannibalised for spare parts to keep the rest running . Tanks damaged during the 1939 Winter War with Finland were also cannibalised for parts . On 1 June 1941 the Red Army had 10 , 268 T - 26 light tanks of all models on their inventories , including armoured combat vehicles based on the T - 26 chassis . T - 26s composed a majority of the fighting vehicles in Soviet mechanised corps of the border military districts . For instance , the Western Special Military District had 1 , 136 T - 26 tanks on 22 June 1941 ( 52 % of all tanks in the district . The T - 26 ( mod . 1938 / 39 , especially ) could withstand most German tanks in 1941 , but were vulnerable to the Panzer III and Panzer IV participating in Operation Barbarossa in June 1941 , and all of the Red Army ' s tank models suffered severe losses due to the complete air supremacy of the German Luftwaffe . The majority of the Red Army ' s T - 26s were lost in the first months of the German - Soviet War , mainly to enemy artillery and air strikes . Many tanks broke down for technical reasons and lack of spare parts . As the war progressed and Germany ' s lighter tanks were replaced by the Panzer III , Panzer IV and heavier tanks such as the Panther , the T - 26 was gradually replaced through attrition by the vastly superior T - 34 . The remaining T - 26s participated in battles with the Germans and their allies during the Battle of Moscow in 1941 – 42 , the Battle of Stalingrad and the Battle of the Caucasus in 1942 – 1943 . Some tank units of the Leningrad Front used their T - 26 tanks until 1944 . The defeat of the Japanese Kwantung Army in Manchuria in August 1945 was the last military operation in which Soviet T - 26s were used . In the 1930s , T - 26 light tanks were delivered to Spain ( 281 ) , China ( 82 ) and Turkey ( 60 ) . They were used in the Second Sino - Japanese War by the Chinese in 1938 – 1944 , especially in the Battle of Kunlun Pass . The Finnish Army used captured T - 26s of different models during the Continuation War , and some tanks served in Finland for various non - combat purposes until 1961 . Captured T - 26s were also used by the German , Romanian and Hungarian armies . Variants . Twin - turreted tanks . As the series production of the PS - 2 gun was delayed , the Main Artillery Agency of the RKKA gave preference to a new gun . It was developed by the Artillery Design Office of the " Bolshevik " Factory , constructed from parts taken from the previously purchased German 37 mm anti - tank gun developed by Rheinmetall and the PS - 2 gun . This system was successfully tested and the Artillery Factory No . 8 named after M . Kalinin started its series production under the designator B - 3 ( 5K ) . The B - 3 gun had less recoil and a smaller breech compared to the PS - 2 , so it could be easily mounted in the normal machine gun turret of the T - 26 . The first twin - turreted T - 26 was armed with a B - 3 gun in the right turret in late 1931 . Unfortunately , series production of the B - 3 gun proceeded slowly due to poor production standards ( none of 225 guns produced in 1931 were accepted by army representatives ; it took until 1933 to complete the original order for 300 guns placed in August 1931 ) . Completed B - 3 guns were mounted on BT - 2 light tanks after mid - 1932 . This meant that twin - turreted T - 26 tanks continued to be equipped with old 37 mm Hotchkiss ( PS - 1 ) guns . As production of the PS - 1 gun had ended , some guns were taken from military supply depots and scrapped MS - 1 ( T - 18 ) tanks . The initial plan was to arm every fifth T - 26 with the 37 mm gun in the right turret , but the final proportion was somewhat higher . About 450 twin - turreted T - 26 mod . 1931 tanks mounting the 37 mm gun in the right turret were produced in 1931 – 1933 ( including only 20 – 30 tanks with the B - 3 gun ) . There were 392 T - 26 mod . 1931 tanks with gun plus machine gun armament in the Red Army on 1 April 1933 . One twin - turreted T - 26 was given to the Research Institute of Communication in March 1932 to develop special tank communication devices . The plan was to equip each tank with a keyphone , while a platoon commander ' s tank would be equipped with a telephone switch for 6 subscribers ( four for the tanks in the platoon , one for communication with infantry and one for contacting headquarters ) . A special terminal block was mounted on the rear of the tank so that communication wires could be connected . The work remained experimental . Single - turreted tanks . The T - 26 mod . 1939 with appliqué armour weighed , which caused an overload of the chassis , transmission , and engine of the light tank . Drivers were advised to use low gears only . During the Great Patriotic War , a mounting of 15 – 40 mm appliqué armour on about a hundred different T - 26s was performed by local factories in Leningrad in 1941 – 1942 , during the Siege of Odessa ( 1941 ) , the Battle for Moscow and the Siege of Sevastopol ( 1941 – 1942 ) . A cutting of armoured plates was more rough than developed during the Winter War ; the majority of these modified tanks did not have a moving armoured gun mask as seen in Factory No . 174 ' s original design , and some tanks had front appliqué armour only . Artillery tanks . It was found that the A - 43 turret was very tight for two crewmembers ; it had insufficient observation field ; there was not any turret ventilation which made continuous gunfire difficult ; and it was hard to rotate the turret manually . At the beginning of 1933 , a new 76 mm KT tank gun mod . 1927 / 32 with reduced ( from 900 mm to 500 mm ) recoil length was installed into the A - 43 turret . The turret was still a very tight place for crew members . The ammunition stowage for 54 rounds was unsuccessful , and the military refused the A - 43 turret . The T - 26 - 4 with the KT tank gun passed tests successfully and five vehicles were built in 1933 – 1934 as pilot batch . Initially it was planned to arm three of these T - 26 - 4 with the 76 . 2 mm KT tank gun mod . 1927 / 32 and the other two tanks with the 76 . 2 mm PS - 3 tank gun . The PS - 3 tank gun was developed at the Experimental Engineering - Mechanical Department ( OKMO ) of the Factory No . 174 by engineer P . Syachentov . The PS - 3 had better specifications in comparison with the series - produced KT tank gun and also had several technical innovations ( foot firing switch , original training gear , travelling position fixing , binocular optical sight ) . The T - 26 - 4 armed with the PS - 3 tank gun was tested in October 1933 but it was found that the PS - 3 was too powerful for the T - 26 light tank — turret ' s race ring and hull roof were deformed during gun fire , and the suspension springs were damaged . It was decided to arm the T - 26 - 4 with the 76 . 2 mm KT tank gun only . All five experimental T - 26 - 4 artillery tanks were tested during military exercises near Leningrad in September 1934 before scheduled series production of 50 such vehicles in 1935 . But on 19 September 1934 an incident with a T - 26 - 4 took place : a blow - back because of shell case destruction during gun fire . Despite the fact that this defect was unrelated to turret design , the military representatives cancelled the order to produce the T - 26 - 4 . Also the work to design turretless AT - 1 artillery tanks armed with the powerful 76 . 2 mm PS - 3 tank gun started at that time . The T - 26 - 4 ' s turret construction was the design used in the series - produced BT - 7A artillery tank . In 1939 , the Armoured Directorate of the Red Army ( ABTU RKKA ) ordered the development of a new conical turret for the T - 26 similar to the BT - 7 ' s turret and to arm it with the 76 . 2 mm L - 10 tank gun . Engineers of the Factory No . 174 felt it was impossible to implement this project because it would lead to a significant overload of T - 26 ' s chassis . Armoured combat vehicles . A large variety of different armoured combat vehicles were developed on the T - 26 chassis in the 1930s . Among them were KhT - 26 , KhT - 130 and KhT - 133 flame - throwing ( chemical ) tanks ( 552 , 401 and 269 vehicles were produced , respectively ) ; T - 26T artillery tractors ( 197 were produced ) ; TT - 26 and TU - 26 remotely controlled tanks ( 162 teletanks of all models were produced ) ; ST - 26 bridge - laying tanks ( 71 were produced ) ; SU - 5 self - propelled guns ( 33 were produced ) ; experimental armoured cargo / personnel carriers , reconnaissance vehicles , and many others . The majority of these vehicles were developed at the Leningrad Factory of Experimental Mechanical Engineering ( from 1935 known as the Factory No . 185 named after S . M . Kirov ) by talented Soviet engineers P . N . Syachentov , S . A . Ginzburg , L . S . Troyanov , N . V . Tseits , B . A . Andryhevich , M . P . Zigel and others . Various vehicle - mounted equipment was developed for the T - 26 , including mine - clearing attachments , inflatable pontoons and a snorkel system for fording water obstacles , devices for overcoming obstacles and many others . T - 26 light tanks were also modified into different armoured combat vehicles in the field during wartime . Survivors . There are about 45 T - 26 tanks of various models preserved in different museums and military schools ( mainly Russian , Spanish , Turkish and Finnish ) . The most notable of them are :