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.
Battle of France
The German Army lacked a formidable heavy combat tank like the French Char B1. In armament and armour, French tanks were the stronger designs and more numerous (although the German vehicles were faster and more mechanically reliable). But while the German Army was outnumbered in artillery and tanks, it possessed some critical advantages over its opponents. The newer German "Panzers" had a crew of five men: a commander, gunner-aimer, loader, driver and mechanic. Having a trained individual for each task allowed each man to dedicate himself to his own mission and it made for a highly efficient combat team. The French had fewer members, with the commander double-tasked with loading the main gun, distracting him from his main duties in observation and tactical deployment. It made for a far less efficient system. Even within infantry formations, the Germans enjoyed an advantage through the doctrine of "Auftragstaktik" (mission command tactics), by which officers were expected to use their initiative to achieve their commanders' intentions, and were given control of the necessary supporting arms.