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.
History of the tank
The German response to the Cambrai assault was to develop its own armoured program. Soon the massive A7V appeared. The A7V was a clumsy monster, weighing 30 tons and with a crew of eighteen. By the end of the war, only twenty had been built. Although other tanks were on the drawing board, material shortages limited the German tank corps to these A7Vs and about 36 captured Mark IVs. The A7V would be involved in the first tank "vs". tank battle of the war on April 24, 1918 at the Second Battle of Villers-Bretonneux—a battle in which there was no clear winner.
Numerous mechanical failures and the inability of the British and French to mount any sustained drives in the early tank actions cast doubt on their usefulness—and by 1918, tanks were extremely vulnerable unless accompanied by infantry and ground-attack aircraft, both of which worked to locate and suppress anti-tank defences.