Early signaling between naval vessels was by prearranged messages transmitted by flags, lights, or the movement of a sail.Codes were developed in the 16th century that were based upon the number and position of signal flags or lights or on the number of cannon shots.

Before the outbreak of World War I, military adaptation of the telephone did take place, but its period of growth had not yet arrived.

Near the close of the 19th century, a new means of military signal communication made its appearance—the wireless telegraph, or radio.

In the 17th century the British admiral Sir William Penn and others developed regular codes for naval communication; and toward the close of the 18th century, Admiral Richard Kempenfelt developed a plan of flag signaling similar to that now in use. In his successful demonstration of electric communication between Washington, D.

Later Sir Home Popham increased the effectiveness of ship-to-ship communication by improved methods of flag signaling.telegraph by Samuel F. C., and Baltimore in 1844, he provided a completely new means of rapid signal communication.

Three years later, in the Indian Mutiny, the newly established telegraph, which was controlled by the British, was a deciding factor.

In the American Civil War (1861–65), wide use was made of the electric telegraph.

The organization and efficiency of the armies varied greatly.

At one end of the scale was Great Britain, with a small but highly developed signal service; and at the other end stood Russia, with a signal service inferior to that of the Union Army at the close of the American Civil War.

It employed two adjustable mirrors so arranged that a beam of light from the sun could be reflected in any direction.