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.
Company (military unit)
In the United States Army, infantry companies are usually made up of three rifle platoons and a heavy weapons platoon; mechanized infantry companies are usually made up of three rifle platoons consisting of four infantry fighting vehicles (IFV) each and a command element containing two IFVs; tank companies are usually made up of three tank platoons consisting of four tanks each and a command element containing two tanks; support companies are typically divided into platoons of specialization that may contain additional special sections. A company is usually commanded by a captain, although in some cases they may be commanded by a first lieutenant or a major. Unlike its component platoons, a company typically has additional positions of supporting staff, such as an executive officer (XO), a first sergeant, a readiness/training NCO, and other positions (e.g., supply sergeant, armorer). The corresponding unit of artillery is always called a "battery". Similarly, the term "troop" is used for cavalry units, including both the horse-mounted units of history as well as modern armored cavalry and air cavalry units.