Frederic Russell Theriault, 89, a cryptanalyst who helped break the code used by the Japanese navy during World War II, died Sept. 1 of a heart attack at Brighton Gardens, an assisted living facility in Oklahoma City where he had been living for the past few months. He was a longtime resident of Hyattsville and Burtonsville.
Dr. Theriault was born in Boston and received bachelor's and master's degrees in chemistry from the University of Massachusetts in the late 1930s. He received his doctorate in food technology in 1942 from the same institution.
In a memoir he wrote for his family in 1999, he recalled that at the outbreak of World War II, he dreamed of being in the cavalry, but "those who knew me in college at the time, remember me as a skinny, near-sighted '4F' type, who was barred from ROTC because of physical disability."
He filled out a government questionnaire designed to locate special talents that would be needed in the war and mentioned that he enjoyed doing cryptograms and other puzzles. That interested the Navy, and in July 1942, shortly after Dr. Theriault received his doctorate and while still a civilian, he reported to the Navy's communications facility in Northwest Washington. He immediately began learning JN25, the fleet command communication system of the Japanese navy.
He was put in charge of a sizable team of WAVES and Navy enlisted men who logged in deciphered messages, though his only supervisory experience, he recalled, had been over "a little group of college men and women repairing damaged books in the college library." He received a commission as a naval ensign shortly thereafter.
"I had a reputation for solving problems caused by garbles where I was first assigned," Dr. Theriault recalled. "For the last three years of the war, my principal duty was making unreadable messages readable. I was good at it, and many messages were read which might otherwise not have been."
Dr. Theriault was especially gratified that the messages he was able to decipher quite likely saved lives. At the end of the war he received a commendation for his accomplishments and a promotion to the rank of lieutenant.
"And then," he wrote, "we began the days of the Cold War, which, for me, developed into a career with the National Security Agency."
He worked for NSA from 1947 to 1977. Although he never revealed to his family what he actually did -- beyond saying that he was in charge of the library -- he did mention that he was the NSA officer on duty the night of April 12, 1961, when the Soviets launched Vostok 1, the world's first piloted spaceship, with cosmonaut Yuri Gagarin aboard. He also was commended in 1968 for his work with the Committee on Scientific and Technical Information of the Federal Council for Science and Technology.
In retirement, Dr. Theriault was involved in various civic activities, including the Prince George's County United Way and the county's Advisory Committee on Aging. For many years, well into his eighties, he volunteered with Meals on Wheels. He also collected coins and loved listening to classical music.
Dr. Theriault's wife, Marjorie Evelyn Warner, died in 1990. She had been one of the WAVES at the Wisconsin Avenue communications facility.
Survivors include three children, Anne Theriault Savage of Reston, John Theriault of Guthrie, Okla., and Rick Theriault of Charlotte; and five grandchildren.