The first full investigation into the methods of radio espionage during the First World War. The rapid development of scientific and technological progress and the militarization of society have significantly increased the role of communications during hostilities. The success of military operations often depended on the quick transfer of orders and information, and the failure of his plans depended on the ability to find out the enemy's intentions. The defeat of Samsonov's 2nd Russian army in East Prussia was the first high-profile success of the German army, and it was carried out on the basis of an intercepted Russian radio telegram. In the future, eavesdropping on telephone and telegraph conversations, radio interference and radio information were actively used on all fronts. The book tells about the methods of radio intelligence and espionage in the First World War. How, depending on the front, certain methods of radio reconnaissance changed, how marine radio telegraphy worked and how naval codes were hacked, how phones were tapped on the Russian (Eastern) and French (Western) fronts, who was responsible for the wiretapping and how the materials received were processed, what radio interference created for enemies and, finally, in what way disinformation was delivered to the enemy. For the first time, the methods of secret war on the air of the First World War are analyzed in detail in a separate edition, which is supplemented by previously unknown photographs.