The outbreak of the First World War heralded the end of the old world in many ways, but the scale and drama of the changes was reaching those concerned gradually. The soldiers were the first to learn the lesson of modernity. The massive use of machine guns and artillery changed the combat tactics, forcing armies to dig into the ground. The use of gases has familiarised mankind with the concept of weapons of mass destruction. The airplane carried the horror of war far to the back of the front, making the civilians, safe until now, an involuntary participant in the struggle. For the first time in the history of mankind, radio has allowed to coordinate actions on a global scale, contributing to turning the conflict into a world war. However, the use of the radio had as many advantages as disadvantages for the fighting parties. Anyone equipped with a radio receiver, an enemy or a friend, could capture messages from hundreds of kilometres away. Therefore, the premiere of the radio in its military function was accompanied by the practical application of cryptology on a scale unknown in previous history.