Which signal would take precedence for occupying a unit commander’s position?

The first substitute takes precedence for occupying a unit commander's position because it is typically designated as the primary alternative should the commander become unavailable or unable to fulfill their duties. This structure is implemented to ensure a chain of command remains clear and effective, allowing for a seamless transition of leadership when necessary. The first substitute often has the most familiarity with the unit's operations and plans, ensuring that decisions can be made swiftly and confidently, which is vital in military or organizational settings.

In contrast, the second and third substitutes rank lower in the hierarchy and would only be called upon if both the commander and the first substitute were unavailable. A security alert signal, while critical for indicating immediate threats or emergencies, does not denote a designated leadership succession, and therefore does not take precedence over the established substitutes for command authority.