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.
Battalion
Prior to the late 1980s, Soviet tank battalions consisted of three tank companies of 13 T-64, T-72 or T-80 tanks each, along with a battalion headquarters mounted in a command tank and a headquarters and service platoon, for a total of 165 personnel and 40 tanks; battalions using the older T-54, T-55 or T-62s tanks had 31 or 40 additional enlisted personnel. However, forces in Eastern Europe began to standardize to a smaller formation with 135 personnel and 31 tanks total, with each tank company consisting of 10 tanks total.