Herbert O. Yardley

Herbert O. Yardley was an American cryptanalyst who served in military signals intelligence during the First World War and subsequently led MI-8, the U.S. State Department and Army codebreaking organization later called the Black Chamber.

MI-8 and public disclosure

MI-8 read foreign diplomatic traffic in the interwar period. After the office closed, Yardley published The American Black Chamber in 1931, a book that made its existence public and helped spur U.S. laws restricting disclosure of cryptanalytic information.

In memoriam

Yardley died in 1958. His career remains useful for understanding both the roots of modern signals intelligence and the tension between operational secrecy and historical accountability.

Timeline

• 1917Serves in U.S. Army cryptologic work during World War I.
• 1919Leads the postwar codebreaking office MI-8.
• 1931Publishes The American Black Chamber.
• 1958Dies.