High Quality Content by WIKIPEDIA articles! William Frederick Friedman (September 24, 1891 November 12, 1969) was a US Army cryptographer (or cryptologist depending on preference). He ran the research division of the Army's Signals Intelligence Service (SIS) in the 1930s, and parts of its follow-on services into the 1950s. In the late 1930s, subordinates of his led by Frank Rowlett broke Japan's PURPLE cipher, thus disclosing Japanese diplomatic secrets beginning before World War II era.