What is the rank of the assistant rifle platoon commander?

The role of an assistant rifle platoon commander typically falls under the responsibilities of a junior officer, specifically at the rank of Lieutenant Junior Grade. This rank is designated for officers who have recently graduated from officer training and are being entrusted with leadership positions, such as serving as assistant platoon commanders, where they engage in tactical planning and management of their platoons.

In this context, the other ranks listed do not align with the duties expected of an assistant rifle platoon commander. A Petty Officer Second Class and Chief Petty Officer are both enlisted ranks within the Navy, focused more on technical skills and leadership within the enlisted ranks rather than direct command of a platoon. Warrant Officers also serve important technical supervisory roles but do not hold the same command responsibilities as a junior officer in a rifle platoon. Thus, the rank of Lieutenant Junior Grade is the correct choice for the role of assistant rifle platoon commander.