Tank
With World War II the multi-turreted tanks proved impracticable, and as the single turret on a low hull design became standard, crews became standardized around a crew of four or five. In those tanks with a fifth crew member, usually three were located in the turret (as described above) while the fifth was most often seated in the hull next to the driver, and operated the hull machine gun in addition to acting as a co-driver or radio operator. Well-designed crew stations, giving proper considerations to comfort and ergonomics, are an important factor in the combat effectiveness of a tank, as it limits fatigue and speeds up individual actions.
Tanks in World War II
The Soviet Union began and ended the war with more tanks than the rest of the world combined (18,000–22,000). At the start of World War II the most common tank in Soviet service was the T-26 (derived from the Vickers 6-ton), lightly armoured and armed with a 45 mm gun capable of penetrating most German tanks at normal combat ranges. Few had radios. The design was mechanically sound although incapable of further development. The BT tank series, based on the Christie suspension system, were usually armed with the same 45 mm gun and were the most mobile tanks in the world. Close-support versions of both tanks existed, armed with 76.2 mm howitzers. However, the BT was at the end of its design life. The Red Army also fielded thousands of light reconnaissance tanks such as the amphibious T-37 and T-38 tanks. These had limited combat value; although highly mobile, they were armed only with 7.62 mm machine guns and had very thin armour. The Red Army also had about 400 T-28 medium, multi-turreted tanks, which were in most respects equal to the German Panzer IV. Again, though, this design dated from 1931 and was obsolete.