During the early period of the Second World War, the Wehrmacht invasion into industrialized Russia threatened the supply of critical war materials and manufacturing plants. Russia's National Defense Committee made a decision to move tank production and associated factories. The location became known as "Tankograd" (Tank City) a nickname acquired for this site situated deep in the Urals. The Russians, with an urgent requirement to reinforce their tank strength, made efforts to simplify tank manufacturing methods. This resulted in many versions of the T34 tank, that differed greatly from each other. One of the more distinctive versions was produced at the Chelyabinsk Tractor Works, "ChTZ" in Tankograd in 1943. This model used a one piece cast turret with pronounced rounding on the edges of the turret roof and a peculiar dip along the lower edge of the turret. This improved turret, had additional periscope and pistol ports, and provided more room and comfort for the crew. A new five-speed transmission with modified clutch was added, replacing four-speed model. Combined with engine improvements, these modifications extended the time between maintenance and repair. With few of the "ChTZ" versions produced, of the thousands of T34/76 tanks manufactured, it is regarded almost as a rarity.