A platoon leader (NATO) or platoon commander (more common in Commonwealth militaries and the US Marine Corps) is the officer in command of a platoon. This person is usually a junior officer — a second or first lieutenant or an equivalent rank. The officer is usually assisted by a platoon sergeant. Some special units, such as specific aviation platoons and special forces, require a captain as platoon leader, due to the nature and increased responsibility of such assignments. Platoons normally consist of three or four sections (Commonwealth) or squads (US).