T - 43 tank The Soviet T - 43 medium tank was a prototype medium tank developed during the Second World War as a possible replacement for both the T - 34 medium tank and KV - 1 heavy tank . The project ' s aim was to build a medium tank with heavier armour , but it turned out that what was needed to counter German advances in tank technology was better armament , and the T - 43 was cancelled in favour of a more heavily armed T - 34 - 85 . Development history . The T - 34 medium tank was the mainstay of Soviet mechanized forces in World War II , produced in huge numbers . In May 1942 , Soviet forces started encountering German tanks armed with the new long 75mm KwK 40 gun which could easily penetrate a T - 34 at long range . In June 1942 , the Soviet Main Directorate of Armoured Forces ( GABTU ) issued a requirement to two tank - design bureaus to compete in designing a " universal tank " , which would combine the heavy armour of heavy tanks with the mobility of the T - 34 medium tank . The SKB - 2 heavy tank design bureau in Chelyabinsk started the KV - 13 program , which two years later resulted in a line of successful Iosif Stalin heavy tanks . The Uralvagonzavod complex in Nizhny Tagil developed the T - 43 medium tank . Uralvagonzavod included the Morozov Design Bureau , the designers of T - 34 , who were able to draw on its previous work on the advanced T - 34M project . T - 34M had been cancelled in 1941 , when Germany invaded the USSR . As the new T - 43 project was given a low priority — the focus was on increasing production of the T - 34 — the first prototype T - 43 was finally completed in March 1943 . The T - 43 was generally similar to the T - 34 , but it had a new armour layout and turret design . It had a space - efficient torsion beam suspension instead of the T - 34 ' s Christie type and a new five - speed gearbox . It also had a three - man turret , with commander ' s cupola for all - round vision , a major improvement on the T - 34 ' s two - man turret in which the tank commander was being constantly distracted with aiming the main gun . Compared to the T - 34 Model 1943 with hexagonal turret , the T - 43 ' s turret armour was increased from 70 mm to 90 mm , hull from 47 mm front and 60 mm sides to 75 mm . It retained the same 76 . 2 mm F - 34 tank gun and , for ease of production , shared at least seventy percent of its parts interchangeably with the T - 34 . But testing at Kubinka showed that the heavier T - 43 couldn ' t match the T - 34 ' s mobility , while its armour was still not heavy enough to stop the German 88mm gun . After the Battle of Kursk , Soviet planners realized that the T - 34 ' s biggest drawback was the ineffectiveness of its 76 . 2mm gun against the frontal armour of the new German Tiger and Panther tanks . What was needed was a more effective gun rather than heavier armour . The T - 43 turret was adapted to mount a more effective 85 mm gun , and to fit on the T - 34 tank hull . The T - 43 project was cancelled , and the new T - 34 - 85 was put into production instead . The decision to improve on an existing design rather than commit to a major retooling of the factories was characteristic of Soviet philosophy which held enormous production level as paramount . While Germany — having double the industrial resources of the Soviet Union — suffered a string of production and logistical difficulties while introducing new , technically superior tank models , the Soviets — maximizing productivity — accepted a compromise by significantly improving their main tank , even though it did not match the new German Panther . The result was that while in May 1944 the Wehrmacht only had 304 Panthers operating on the Eastern Front , the Soviets were producing T - 34 - 85 tanks at a rate of 1 , 200 per month . When the T - 34 - 85 first appeared in combat , German intelligence initially misidentified it as the " T - 43 " , based on reports about Soviet tank research .