From the longer Wikipedia page , which includes information on his career in cryptoanalysis. (There are also long discussions on the talk page.)
William Frederick Friedman (September 24, 1891, Kishinev, Bessarabia – November 12, 1969) was a US Army cryptographer who 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 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.
As a child, Friedman was introduced to cryptography in the short story "The Gold-Bug"  by Edgar Allan Poe.
He studied at the Michigan Agricultural College (known today as Michigan State University) in East Lansing and received a scholarship to work on genetics at Cornell University. Meanwhile George Fabyan (Wikipedia page ), who ran a private research laboratory to study any personally interesting project, decided to set up his own genetics project and was referred to Friedman. Friedman joined Fabyan's Riverbank Laboratories outside Chicago in September 1915. As head of the Department of Genetics, one of the projects he ran studied the effects of moonlight on crop growth, and so he experimented with the planting of wheat during various phases of the moon.
Another of Fabyan's pet projects was research into secret messages which Sir Francis Bacon  had allegedly hidden in various texts during the reigns of Elizabeth I and James I. The research was carried out by Elizabeth Wells Gallup . She believed that she had discovered many such messages in the works of William Shakespeare, and convinced herself that Bacon had written many, if not all, of Shakespeare's works.
Friedman spent much of his free time trying to decipher the famous Voynich Manuscript, written sometime between 1403-1437. However, after four decades of study he finally had to admit defeat, contributing no more than an educated guess as to its origins and meaning. Created the first major transcription alphabets [[to equate the Voynich characters with Latin characters in order to help with cryptanalysis, such as the European Voynich Alphabet in the 1940s, where each line of the manuscript was transcribed to an IBM punch card to make it machine readable.
Friedman retired in 1956 and, with his wife, turned his attention to the problem that had originally brought them together: examining Bacon's supposed codes. Together they wrote a book entitled The Cryptologist Looks at Shakespeare which won a prize from the Folger Library and was published under the title The Shakespearean Ciphers Examined.. The book demonstrated flaws in Gallup's work and in that of others who sought hidden ciphers in Shakespeare's work. (There is a discussion on the Wikipedia talk page.)
Married to Elizebeth Friedman
The Friedmans donated their archives to the George C. Marshall Foundation (Wikipedia page )