Radio Support.
Project Gutenberg EPUB3 edition
Linebarger, Paul Myron Anthony
... the first attempt to coordinate artillery, leaflet and radio propaganda. The station had learned the location of the billets of various [Nazi] units in the town, together with the names of their key personnel. With this information, a "game" was arranged with the artillery. One day, at a certain time, these units were addressed by name and their members were told to go outside their buildings and five minutes later they would receive a message. Precisely, five minutes later, leaflet shells released the messages advising surrender. The ability of the Americans to do things like that impressed the German soldiers with their hopeless position more than words.
Obviously, such an operation required close contact with the enemy, plus known possession of standard-wave radio receivers by enemy personnel.