Throughout history, armies and navies have sent messages across battlefields.
Simple orders like “Advance” or “Retreat” could be given by bugle calls or cannon-fire.
But sending reports of the battle back to headquarters needed a different system.
During the 1790’s, a Frenchman called Claude Chappe invented a signaling system called semaphore.
This was a system of sending signals by means of two jointed arms at the tops of tall posts. These arms could be moved to different positions to show different letters of the alphabet.
Each semaphore station was built on a hill so that it could be seen, using a telescope, from the next station in any direction. In this way, messages could be relayed over long distances from one station to the next.
Semaphore stations on the coast would send messages to ships at sea.
On the battlefield, there might not be a semaphore station, but messages could be sent by stationing signalers with large flags on nearby hills.
They used the same code as the semaphore arms.
An expert signaler could send or receive up to 25 letters a minute and messages could be relayed nearly 155 miles (250 kilometers) in 15 minutes.