This exhibit details the checkered career of Herbert
O. Yardley (1889-1958), who headed the highly secret MI-8, or the "Black Chamber." Yardley began his career as a code clerk with the U.S. State Department, and during that service discovered his natural talent as a cryptanalyst. During World War I, Yardley served in the cryptologic section of Military Intelligence (MI) with the American Expeditionary Forces.
After the war, Yardley lead the first peacetime cryptanalytic organization in the United States, MI-8. Funded by the Army and the State Department, MI-8, was disguised as a New York City company that made commercial codes for businesses. However, their actual mission was to break the diplomatic codes of different nations. A mission they were initially quite successful at completing, breaking codes from several foreign countries.
MI-8 had an early success: in 1921-22, Yardley and his staff solved the cipher system used by Japanese negotiators at the Washington Naval Conference. They fed the decrypts to the U.S. chief negotiator, Charles Evans Hughes. The messages contained the Japanese’s minimum demands at the conference. Hughes appeared to be outsmarting the Japanese to obtain a more favorable agreement on naval capital ships, when actually he was reading their negotiating position every day before he went into the bargaining sessions.
In 1929, the State Department closed down MI-8. According to legend, Secretary of State Henry Stimson at that time spoke the famous sentence: “Gentlemen do not read each other’s mail.” Disappointed, unemployed, and accustomed to luxury, Yardley found himself in need of finances and in possession of his country’s secrets. He wrote The American Black Chamber, which revealed to the world the work of MI-8. It became an international best seller. Needless to say, the Army, which continued codebreaking, was not amused. And the Japanese, for their part, changed their code systems. Surprisingly, at the time, the wording of the espionage laws contained a loophole that prevented the government from prosecuting Yardley.
Yardley, a brilliant cryptanalyst, as well as a promoter of the cryptologic cause, continued to provide expertise to various countries, but never again worked for the United States.