It soon became apparent that wireless telegraphy was not an unmixed blessing to armies and navies, because it lacked secrecy and messages could be heard by the enemy as well as by friendly forces.
This led to the development of extensive and complicated The onset of World War I found the opposing armies equipped to a varying degree with modern means of signal communication but with little appreciation of the enormous load that signal systems must carry to maintain control of the huge forces that were set in motion.
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 major powers throughout the world were quick to see the wonderful possibilities for military and naval signaling.
The beam was interrupted by a key-operated shutter that permitted the formation of the dots and dashes of the Morse code. Because consistency and regularity of sunshine were important, the heliograph was never widely adopted throughout the armies of continental Europe.Military communication has thus long played an important role in warfare.Messengers have been employed in war since ancient times and still constitute a valuable means of communication.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.