Tank
Most modern tanks most often have four crew members, or three if an auto-loader is installed. These are the:
Historically, crews have varied from just two members to a dozen. For example, pre-World War II French tanks were noted for having a two-man crew, in which the overworked commander had to load and fire the gun in addition to commanding the tank. First World War tanks were developed with immature technologies; in addition to the crew needed to man the multiple guns and machine guns, up to four crewmen were needed to drive the tank: the driver, acting as the vehicle commander and manning the brakes, drove via orders to his gears-men; a co-driver operated the gearbox and throttle; and two gears-men, one on each track, steered by setting one side or the other to idle, allowing the track on the other side to slew the tank to one side.
Tank corps (Soviet Union)
On 31 March 1942, orders were given for the reformation of the tank corps, as a result of the Soviet need for massed armored units so that the small tank brigades, which were now the basic armored formation, could be capable of decisive actions. The 1st, 2nd, 3rd, and 4th Tank Corps were to consist of a headquarters, two tank brigades, and a motor rifle brigade, authorized a total of 5,603 men with 20 KV heavy tanks, 40 T-34 medium tanks, and 40 T-60 or T-70 light tanks. The new tank corps lacked artillery, reconnaissance and engineer units, and rear support elements, although its component brigades included such formations. They were the equivalent of small Western armored divisions. The motor rifle brigade was a new unit type intended to retain captured positions and to neutralize enemy infantry and anti-tank weapons.