1929–1931: A Transition Period in U.S. Cryptologic History

Abstract

The years 1929 through 1931 were among the most turbulent in American cryptology. During this period, the joint War and State Department Cipher Bureau of Herbert Yardley was closed. The Army created the Signal Intelligence Service under William Friedman. Finally, the Army and Navy began their first tentative steps towards inter-service cooperation. This article examines these events in detail and also takes a look at the relationship between Yardley and Friedman.

Keywords:

• American Black Chamber
• codes
• cryptology
• Herbert O. Yardley
• Laurance Safford
• OP-20-G
• Signal Intelligence Service
• William F. Friedman

Acknowledgements

I would like to thank the library staff at Knox College for their patient and professional help in finding copies of many of the articles and letters referenced here. I would also like to thank the staff of the National Archives and Records Administration (NARA) in College Park, MD, Librarian René Stein at the Research Library at the National Cryptologic Museum in Ft. Meade, MD, and Paul Barron and Jeffrey Kozak of the George C. Marshall Foundation Research Library in Lexington, VA for their excellent help. This research was funded in part by a grant from the Andrew W. Mellon Foundation and by the Office of the Dean of the College at Knox College. An abbreviated version of this article was originally presented at the NSA Center for Cryptologic History Symposium, 7 October 2011.

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Notes on contributors

John F. Dooley

John F. Dooley is the William and Marilyn Ingersoll Professor of Computer Science at Knox College, Galesburg, Illinois. His research interests are in software development, the history of cryptology, computer security, cryptology in fiction, and computer science education.