The T-34, some say the greatest tank of the war and with good reason.
The first production T-34 rolled off the line in September 1940, in Kharkov. This was the T-34/76 Model 1940. The suspension needs a special mention, it was designed in New Jersey, and sold to the Soviet Union, it was the Christie tank system. This along with the wide tracks on the T-34 allowed it transverse terrain of all kinds, in all weather when their enemies tanks might struggle. The frontal armour was 45mm, and on the chassis front it was set back at 60 degrees giving it a strength of 75mm, almost invunerable in 1940.
Moving on to the last model T-34, the T-34/85. Now this was a distinct improvement over the T-34/76, it had a more powerful cannon and a slight increase in armour. It also had a three-man turret, replacing the two-man turret of the T-34 which gave it huge problems, with aiming and commanding.
The 85mm D-5 on the T-34 was capable of piercing 100mm at 914m. Not as good as the Pz.kwpf IVs cannon. The speed was 50km/h and it had a range of 190 miles. It was reliable, but not as durable as the Pz. IV. It was easier to maintain, and it's wide tracks, which were even wider on the /85, made for good cross-country capability.
Not all T-34s had optics or radio, commanders were seen using flag signals on the battlefield. Which lets the T-34 down greatly, but it was a great tank. And a very simple design.
Not used for many improvements, but the T-44, SU-85 and SU-100 did come off the T-34. The simple design gave it a production to over-shadow any other at 53, 382 T-34s between 1940 and 1945.
The M4 is next...