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How did the telegraph and telephone change the work of military commanders?

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tactics Sumerian phalanx, a block of foot soldiers depicted standing shield-to-shield, presenting spears, and advancing in a dense mass, detail from the Stele of the Vultures, limestone bas-relief, c. 2450 bce; in the Louvre Museum, Paris.

The introduction of the telegraph and telephone fundamentally transformed military command by replacing slow, mounted messengers with near-instantaneous wire communication. This shift allowed commanders to exercise active control over armies spread across vast distances, often measured in tens of miles, rather than relying on direct observation from the front lines.1

As a result, the role of the commander shifted from a tactical leader participating in combat to a bureaucratic manager operating from the rear. Commanders moved from the field to offices, where they directed operations by analyzing reports and maps rather than observing the battlefield firsthand. This transition replaced the traditional coup d’oeil—the ability to make decisions by "casting a glance" at the battlefield—with a more deliberate "estimate of the situation".1

While these technologies enabled greater coordination, they also favored defensive warfare. Because wired systems were immobile and vulnerable to artillery fire, they tethered commanders to fixed headquarters, often keeping them far from the front. This trend toward remote command persisted until the interwar development of radio, which eventually allowed commanders to regain mobility and provide leadership at decisive points.12