This date in history: Herbert O. Yardley

On this date in history, 10 May 1941, Herbert Osborn Yardley came to Ottawa to discuss setting up Canada's first code-breaking organization, the Examination Unit (XU). Yardley was an American citizen who had worked as a code-breaker for the U.S. Army during the First World War and subsequently headed the United States' first peacetime code-breaking organization, MI-8. Left out of work when MI-8 was shut down in 1929, in 1931 he wrote a book about his code-breaking exploits, The American Black Chamber, that to the consternation of the U.S. government quickly became an international bestseller.

The Canadian government recruited Yardley to run the XU at the suggestion of the U.S. Army's Chief Signal Officer, Major General Joseph Mauborgne. The XU began operations under Yardley's direction on 9 June 1941, focusing initially on Vichy French codes, German agent traffic, and Japanese diplomatic messages. Unfortunately for Yardley, however, it very soon was made clear to Ottawa that neither the U.S. government (despite Mauborgne's recommendation of Yardley) nor the British government had any intention of co-operating with Canada on code-breaking as long as the author of The American Black Chamber was associated with the effort. In December 1941 Yardley was shown the door. He was replaced by British-supplied cryptanalyst Oliver Strachey in January 1942.

Yardley remained blacklisted from Western code-breaking work for the rest of his life, but in 1999 he was posthumously inducted into the NSA's Hall of Honor as "one of the pioneers of modern American cryptology." A biography of Herbert Yardley, The Reader of Gentlemen's Mail: Herbert O. Yardley and the Birth of American Codebreaking, was published in 2004.