From Wikipedia: "William F Friedman was a US Army cryptographer who ran the research division of the Army's Signal Intelligence Service (SIS) in the 1930s, and parts of its follow-on services into the 1950s. In 1940, subordinates of his led by Frank Rowlett broke Japan's PURPLE cipher, thus disclosing Japanese diplomatic secrets before America's entrance into World War II."
Wikipedia: https://en.wikipedia.org/wiki/William_F._Friedman
Friedman Legacy (226 page PDF) at NSA.gov: https://www.nsa.gov/Portals/70/documents/resources/everyone/digital-media-center/video-audio/historical-audio/friedman-legacy/friedman-legacy-transcript.pdf
Audio records and transcripts at NSA.gov: https://www.nsa.gov/resources/everyone/digital-media-center/video-audio/historical-audio/friedman-legacy/
Public Domain, Link