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.
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.