#10: William Friedman – The Purple Code
Purple Code was Japan’s top-secret diplomatic cipher in World War II, designed to scramble messages so thoroughly that Allied interception seemed useless. Enter William Friedman, the quiet mastermind of U.S. codebreaking. Without ever seeing the machine, his team reconstructed it through pure analysis, turning intercepted signals into readable intelligence. The mystery wasn’t just the code, but the machine behind it. The impact was decisive. U.S. officials gained access to high-level Japanese communications, shifting the balance of wartime intelligence in ways few ever saw.
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