SPY Historian Mark Stout explores the importance of signals intelligence (SIGINT) to the Vietnam War with retired National Security Agency cryptanalyst Tom Glenn. Glenn served more time in country than any other civilian of the NSA. Hear about the sixth sense that good SIGINTers need to have, the difficulties of working in foreign languages, and how Glenn and his colleagues were able to predict every major Communist offensive. Learn also why American commanders did not always believe them. Finally, hear the wrenching story of Glenn’s last days in Saigon in 1975 as the city was falling to the North Vietnamese Army.