 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.