Military command is the principle of the exercise of authority in a military, naval or air force context. The exercise of command is normally articulated in the legal framework which embodies the force concerned.

Command is normally exercised at all rank levels in the hierarchy

Hierarchy

A hierarchy is an arrangement of items in which the items are represented as being "above," "below," or "at the same level as" one another...

 where authority to exercise command is vested in the rank held by the individual.

The term command can also refer to the instruction or order promulgated through the command chain; Directed letter, general order

General order

In militaries, a general order is a published directive, originated by a commander, and binding upon all personnel under his command, the purpose of which is to enforce a policy or procedure unique to his unit's situation which is not otherwise addressed in applicable service regulations, military...

, Operational Order (OpOrder) or the spoken instruction given by a superior to a subordinate.

A command is the name given to the extent of authority by a given senior military officer such as a Squadron, Regiment or ship or higher formation such as Land Command or Navy Command

Commander-in-Chief Fleet

Commander-in-Chief Fleet is the admiral responsible for the operation, resourcing and training of the ships, submarines and aircraft, and personnel, of the British Royal Navy...

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