I’m an occasional history buff, and I’m just finishing up “The Zimmerman Telegram” by Barbara Tuchman.
It’s an interesting story about an incident in World War 1 when the Germans approached Mexico attempting to involve them in a war with the US, to keep the US busy on this side of the Atlantic.
The Brits learned of the communications through a broken German code, and the real challenge was finding a way to use the information without revealing that the code had been broken.