Marine Corps Unit Structure Marine Corps forces vary in the organization depending on the needs and manpower of a unit: Marines' smallest division is a fire team, which is three Marines and a team leader, usually a corporal.Three fire teams (12 Marines) comprise a squad led by a squad leader, usually a sergeant.Three squads (39 Marines) comprise a platoon with a leadership team of a platoon sergeant and platoon commander (usually a 1st or 2nd lieutenant). The platoon leadership also benefit...