At first, the messages looked similar to the thousands of smuggling messages she had solved before. They used the same kinds of call signs and similar frequencies. But after a brief period of confusion, Elizebeth realized that the messages hadn’t been sent by smugglers at all. The plaintexts were in German. They contained sensitive information about the routes of U.S. and British ships and the capacities of U.S. factories. And according to the bearing fixes, the signals originated from unknown radio stations in Mexico, South America, and the United States.
