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HomeHistoryCryptologic HistoryHistorical FiguresHistorical Figures View

# NSA Historical Figures

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# CAPT Thomas H. Dyer, USN

##                 2002 Hall of Honor Inductee            

As the lead cryptanalyst at Station HYPO in Hawaii from 1936 to 1945, Thomas H. "Tommy" Dyer led the team that was responsible for most of the breakthroughs in reading Japanese naval communications during the war in the Pacific. After the war, he continued a brilliant career and went on to be one of the three primary cryptanalytic trainers, along with William Friedman and Lambros Callimahos, for both Armed Forces Security Agency (AFSA) and National Security Agency.

Born in Osawatomie, Kansas, in May 1902, Thomas Dyer graduated from the Naval Academy in 1924. After serving tours as a radio or communications officer, he was assigned to the Department of Naval Communications' cryptanalytic organization, OP-20-G, in May 1931. There he trained under Agnes Driscoll and developed procedures for using IBM tabulators to ease the burden of sorting through the myriad of possible solutions for breaking codes and ciphers. This earned him the accolade "the father of machine cryptanalysis."

In July 1936, Dyer transferred to the 14th Naval District's Fleet Radio Unit in Hawaii, soon to be called Station HYPO. During the next nine years, his accomplishments were extraordinary. In 1938, he branched out from HYPO to form the Communications Intelligence Unit in Pearl Harbor, with both intercept and direction-finding stations at Heiia and Wahiawa. In early 1941, when Commander Joseph Rochefort became the Officer in Charge (OIC) of Station HYPO, Dyer remained as assistant OIC and chief cryptanalyst. Under Dyer's supervision, HYPO began contributing essential elements of information derived from the JN-25 code to Admiral Nimitz before the Battle of the Coral Sea. By 27 May 1942, HYPO had developed such a detailed picture of the Japanese plan for the occupation of Midway that Nimitz's intelligence officer was able to predict almost precisely when and where the enemy would strike. Dyer was also directly involved with the interception, decryption, and subsequent intelligence information reporting which led to the shootdown and death of Fleet Admiral Isoroku Yamamoto. Dyer's work also resulted in the breaking of the Japanese merchant shipping and transport code and the main Japanese weather code.

From February 1946 to June 1949, Dyer was assigned to the Naval Security Station, Communications Support Activity in Washington, DC (precursor to the Naval Security Group) as chief of processing and technical director. In 1947, he was designated as one of the first Navy Special Duty Officers (Cryptology). Dyer was a leading member of the Navy contingent that joined the fledgling Armed Forces Security Agency in June 1949 and, along with Captain Laurance Safford, was in charge of all daily AFSA operations.

Later, at NSA, he established the Agency's first academic training program (college and National Cryptologic School courses) for Agency employees. From October 1952 to January 1954, he was chief, NSA Far East, Tokyo. He returned to NSA Washington in February 1954 to become its first historian and remained there until his retirement from the Navy in February 1955.

Captain Dyer passed away in 1985.

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### Related Link:

                              - Learn more about the Midway Exhibit and other National Cryptologic Museum exhibits.

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2002Thomas H. Dyerhall of honorBiographyhistorical figure