What factor primarily determines an individual's authority of command?

The primary determinant of an individual's authority of command is their grade and assignment within the military structure. In the Army, rank signifies the level of responsibility assigned to personnel and dictates their authority over subordinates. Higher grades come with increased responsibilities and decision-making power, which are essential for effective command.

The assignment, or the specific role a soldier holds, also directly influences their command authority. An individual assigned to a leadership role, regardless of experience, education, or personal attributes, inherently possesses the authority associated with that position. This established hierarchy ensures that commands flow through a structured system, maintaining order and discipline within the ranks.

While experience, education, popularity, and leadership styles can enhance a leader’s effectiveness, they do not fundamentally alter the structural authority established by rank and assignment, making grade and assignment the correct choice for this question.