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.
Tank desant
Today, tank desant is considered a wasteful and human-costly improvisation, which, in the opinion of some writers, was adopted by the Red Army because they failed to appreciate the problem of tank–infantry cooperation. However, this is not supported by historical analysis, and there is evidence that tank desant was used as early as 1937 during the Spanish Civil War. On 13 October, during the Aragon Front advance in the area of the Fuentes de Ebro, the 1st Independent Tank Regiment (Republican Army), using BT-5 tanks attached to the XV International Brigade, conducted a tank desant mission with the attached 24th Infantry Battalion of the Spanish army ("24ta de Voluntarios", commanded by Captain Aquilla). But lack of coordination and communication between the Soviet crews, who had just completed a march, and the Spanish infantry resulted in sixteen tanks being either destroyed or disabled (some salvaged) and 37 tank crewmen becoming casualties.