Which of the following determines the purpose and organization of the interior guard?

The purpose and organization of the interior guard are fundamentally determined by the Commander's discretion. This authority is rooted in the Commandant of the Marine Corps' guidance and the applicable orders that set the framework for security and protection within military installations. The Commander assesses various factors such as the specific mission, potential threats, and the environment to establish an interior guard that meets the needs of the unit while ensuring safety and security.

While the Marine Corps Handbook provides useful guidelines and the local military regulations may offer specific provisions relating to the interior guard, it is ultimately the Commander's judgment that tailors these resources to the unique circumstances of a situation. This allows for adjustment and flexibility in operations based on real-time assessments of the security landscape, which is crucial for effective military readiness and response. Consensus among officers might assist in decision-making, but authoritative direction comes from the Commander, reinforcing the chain of command and ensuring accountability in security measures.