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American Black Chamber (Annotated – Digital)


Subject: Cryptology

Returning from France after working as the head of the cryptologic bureau of the American delegation to the Paris Peace Conference in the spring of 1919, Herbert O. Yardley called for the formation of a peacetime cryptologic bureau. Aware of the desperate need for a permanent code and cipher section of the Military Intelligence Division of the War Department, acting Secretary of State Frank L. Polk approved the creation of what came to be known as “The American Black Chamber” in May of 1919. Yardley, the head of the cryptologic section of the Military Intelligence Division (MI-8) during World War I, recruited many of his wartime subordinates to work in the Black Chamber’s New York offices. Despite its relatively small staff and budget (under a third of a million dollars of State and War Department funds from 1919 to 1929), the Black Chamber was incredibly prolific: Yardley claimed that, including its wartime work as MI-8, the Black Chamber intercepted and decoded more than 45,000 foreign telegrams.

President Herbert Hoover’s nomination of Henry L. Stimson as Secretary of State led to the end of the American Black Chamber. When Henry L. Stimson learned about the Black Chamber’s existence and activities, he immediately suspended its State Department funding, famously exclaiming, “Gentlemen do not read each other’s mail.”

The demise of the Black Chamber left Yardley unemployed and penniless. Desperation impelled him to publish a tell-all story of the activities of the American Black Chamber. In doing so, he exposed numerous confidential and embarrassing state secrets. The revelations published inThe American Black Chambersignificantly damaged American foreign relations with Japan and other nations, which were unaware of the Black Chamber’s existence and its ability to decipher their encrypted diplomatic messages.

William F. Friedman and other members of the cryptographic community were outraged by what they saw as a desperate and self-aggrandizing effort. Not only had Yardley revealed important state secrets; he had overstated and dramatized his own role in the decipherment of codes in the American Black Chamber and misconstrued crucial aspects of the cryptographic work done during and after the war.

The William F. Friedman Collection contains important historical information about the American Black Chamber. Friedman’s correspondence with Yardley and others reveals the distortions contained in The American Black Chamber. Of significant importance are Friedman’s copy of The American Black Chamber, which includes marginalia penned by eminent cryptographers of the time; Friedman’s correspondence with Yardley; and Friedman’s correspondence with Charles J. Mendelsohn, and John M. Manly, each of whom worked closely with Yardley in MI-8. The collection also houses material documenting Yardley’s contributions to the field of cryptography, and his popular publications after resigning his military commission.

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American Black Chamber (Annotated - Digital)


Language: english