After the invention of the telegraph, the next major technological development in the science of telecommunications was the radio, invented by Guglielmo Marconi in the closing years of the 19th century. The invention of the radio was a marvelous discovery, but the military viewed its existence as both ripe for exploitation and, at the same time, rife with probable security threats: “[T]he all-pervasive property of radio is also its greatest military weakness, because messages will inevitably reach the enemy as well as the intended recipient” (146). The use of radio for military purposes was first widely deployed during the First World War, and the first method of radio encryption was the use of a German cipher typically known as the ADFGVX cipher.

During the war, the warring nations commissioned coalitions of military cryptologists and analysts. The French coalition was widely regarded as the most skilled group in Europe, developing a method of identifying telegraph operators by the way they transmitted messages. Additionally, radio analysis also led to the use of what is known as traffic analysis, whereby the source of a message (and possibly its destination) could be discovered even while the encrypted message remained a mystery.