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.
Armoured warfare
Tanks rarely work alone; the usual minimum unit size is a platoon (platoon is the smallest US Army/Marine unit led by an officer, and a component of a company or troop) of three to five tanks. The tanks of the platoon work together providing mutual support: two might advance while covered by the others then stop and provide cover for the remainder to move ahead.