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.
Tanks in the Spanish Army
The first foreign tanks to enter service with the Nationalists were five Italian CV-33s, which arrived at the city of Vigo on 26 August 1936. These arrived with ten crewman, whom would serve as instructors. The tanks were armed with two machine guns and had a maximum of of steel armor. On 10 December 1936, Italian dictator Benito Mussolini decided to send combat troops to Spain, in a bid to end the war as early as possible. These men were organized into the "Corpo Truppe Volontarie" (CTV; Volunteer Corps), and by the end of the year their ranks had swelled to an estimated 47,000 men; 20,000 of which came from the Italian Army, and 27,000 of which originated from the Blackshirts. The corps was put under the command of Italian General Mario Roatta. The first major battle for the CTV came in March 1938, when it decided to engage Republican forces during the Battle of Guadalajara. A force of some 35,000 men, including 81 tanks, attacked on 8 March 1937. Failing to take into account the meteorological conditions of the battlefield, by the following day the Italian troops found themselves attacking over ground that had turned into mud due to the heavy rains. The slow speed of the advance allowed the Republican Air Force to persistently raid advancing Italian forces, dispersing entire columns off the main roads and forcing them to stall in the mud. A Republican counterattack on 18 March, led by Pavlov's armored brigade, forced the Italians to withdraw. Nationalist air support failed to provide close air support for Italian troops because runways had become water-logged, while Italian armor proved no match against the heavier and faster T-26 and BT-5 tanks. Officially, the Italians lost an estimated 2,700 soldiers during the campaigning around Guadalajara; the Republican Army lost an estimated 4,000. According to other sources, the CTV lost an estimated 5,000 casualties during the battle. However, armor losses were relatively low, as the Republicans lost 7 T-26s and the Italians lost 19 CV-33s. Despite this initial setback, the Italian government continued the supply of personnel and equipment to the CTV in Spain, and by late 1938 the Italian volunteer's corps was equipped with three tank battalions. By the end of the war, a total of 155 CV-33s were delivered to Spain.