What principle requires each person to have only one direct supervisor?

The principle that requires each person to have only one direct supervisor is known as unity of command. This concept is essential in organizational structures, particularly in emergency services and incident management. Unity of command ensures that an individual reports to one supervisor only, which minimizes confusion regarding direction and authority. This clear line of authority promotes accountability and ensures that instructions are clear, reducing the likelihood of conflicting orders that could arise if an individual were to report to multiple supervisors.

Additionally, unity of command enhances coordination and communication within teams, as each member understands their role and who they are directly accountable to. This principle is fundamental to maintaining an organized and efficient operation, particularly in high-stress environments like firefighting, where effective communication and swift decision-making are vital for success and safety.