Many world war ii film and television works talk about deciphering passwords, especially spy films. How did you break the code?

If you are talking about message code, then this decoding method should be similar to the interpretation of ancient Chinese characters. That is to say, according to the frequency of occurrence of specific characters. The most common characters are decoded first. And so on. It's easy to say after reading a sentence. This word is the key word. You can have a look at my contents. Those words with high frequency are arranged in series with other words to be classified. Any encrypted information is a language. Every language has its own rules. Although there are many languages. But for professionals, it's just a manual problem. So once the key characters are decoded. It's easy to decipher the information code. (There are also extremely remote languages, which increase the difficulty of decoding. I remember a movie called Whisperwind. You can have a look)

If you are interested, I suggest you buy professional books to read.