The National Security Medal is a decoration of the United States of America officially established by President Harry S. Truman in Executive Order 10431 of January 19, 1953. The medal was originally awarded to any person, without regard to nationality, for distinguished achievement or outstanding contribution on or after July 26, 1947, in the field of intelligence relating to the national security of the United States.

William Frederick 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.