The correct answer is "Battalion."
The word that best matches the definition is "Battalion."
The difference with the Platoon is that the Platoon is a subdivision of a military unit and usually has two or more squads. Frequently, the leader of a platoon is a second lieutenant.
Hierarchical authority in the military is of the utmost importance because it is the only way to guarantee that orders are followed. That is why in the military exists the concept of the "span of command." This is the number of subordinates one leader can control and exert orders. This is the success of the military, the chain of command. Everybody knows who the immediate chief is and everybody has to follow orders thoroughly to be successful in a mission.