Corbett defines sea command through maritime communications

Corbett defines command of the sea through control of communications that matter to the belligerents. A fleet cannot occupy the sea as an army occupies conquered territory, live from it in the same way, or exclude neutral states altogether. Its strategic value lies in movement between states and between parts of a state. Except in an almost entirely maritime war, sea command serves wider objectives. Fleet operations can assist or obstruct military action ashore, protect or attack commerce, and persuade or deter neutral powers from entering the conflict.