Radio codes
The radio was not only used for propaganda and speaking. It was also used to transmit war strategies and plans from one country to another. Countries were capable of picking up on other countries' radio frequencies, so to prevent enemies from understanding secret information, countries all coded their messages over the radio. The German's used a machine called the Enigma to make codes while the SIGMA, a device used to form codes as well, was used by America.
In the 1930s, a group of expert Polish code breakers: Jerzy Rozycki, Henryk Zygalski, and Marian Rejewski, solved German codes made by the Enigma with the assistance of a German traitor. They shared the information they decoded with France and Britain. The Germans were never positive that the Allies had decoded their messages but started to catch on when things didn't always go according to plan. Decoders figured out some Japanese messages, but they did not contain enough information at the time to alert the Americans of Pearl Harbor.
In the 1930s, a group of expert Polish code breakers: Jerzy Rozycki, Henryk Zygalski, and Marian Rejewski, solved German codes made by the Enigma with the assistance of a German traitor. They shared the information they decoded with France and Britain. The Germans were never positive that the Allies had decoded their messages but started to catch on when things didn't always go according to plan. Decoders figured out some Japanese messages, but they did not contain enough information at the time to alert the Americans of Pearl Harbor.