US Navy Cryptanalytic Bombe

The 120 machines, the U.S. Navy’s Cryptanalytic Bombes, were seven feet high, two feet wide, and ten feet long. Each one weighed 5,000 lbs. The following photo with one of the WAVES in front of the machine gives an idea of the size of the machine. In person I find it intimidating.

US Navy Cryptanalytic Bombe

High res photo of bombe

The front and back of the Bombes each had eight columns of four rotors. The top wheel mimicked the Enigma’s new fourth rotor while the bottom commutator represented the rightmost, or fastest, rotor of the Enigma. The bottom rotor spun at a speed of approximately 1,725 revolutions per minute, which allowed the machine to complete its run in only twenty minutes.

A closeup of the Bombe from the front, taken by the Navy, with parts labelled

Right-click the image and open in a new window for a full page size view.

Rearview of the bombe, parts labelled. Never fails to amaze me.

Much reliable information can be found in a booklet written by Jennifer Wilcox, Assistant Curator at the National Cryptologic Museum. The text of this booklet can be found History of the Cryptanalytic Bombe.

There is much new information about the US Bombe online now. One site which has really explained a great deal to me is US Navy Cryptanalytic Bombe – A Theory of Operation and Computer Simulation, an analysis written by Magnus Ekhall and Fredrik Hallenberg. I did not realize until I read this how shallow my understanding of the bombe in operation was.

The Bombe currently on display at the Nat’l Crypto Museum

Because so much excellent information is available through the NSA web site, I have taken the liberty of reproducing their index here. I recommend their publications as a primer of documented facts. PDF or text file versions are available for most of the monographs and brochures. Printed copies of publications marked with an asterisk (*) may be requested from the Center for Cryptologic History via email at Rather than include links with this list that can become outdated I’ve just listed the titles. All links can be found at the Publications Index Page. (This link frequently changes; just search for “Center for Cryptologic History publications”)

Subject Title Author Date
Bombes The Secret of Adam and Eve Jennifer Wilcox 2003
Cipher Machines German Cipher Machines of World War II * David Mowry 2003
Code Talkers Origins of the Navajo Code Talkers Patrick Weadon 2002
COMINT A History of US Communications Intelligence during WWII: Policy and Administration Robert Louis Benson 1997
Enigma The Cryptographic Math of the Enigma Dr. A. Ray Miller 2019
Enigma The First Americans: The 1941 US Codebreaking Mission to Bletchley Park David Sherman 2016
Enigma Solving the Enigma-History of the Cryptanalytic Bombe Jennifer Wilcox 2001
Mathematics How Mathematicians Helped Win WWII John Clabby 2005
Holocaust Eavesdropping on Hell: Historical Guide to Western Communications Intelligence and the Holocaust, 1939-1945 Robert Hanyok 2004
Mathematics How Mathematicians Helped Win WWII John Clabby 2005
Midway The Battle of Midway: AF is Short of Water Patrick Weadon 2000
Pearl Harbor Pearl Harbor Revisited: United States Navy Communications Intelligence, 1924-1941 Frederick Parker 1994
Pearl Harbor West Wind Clear: Cryptology and the Winds Message Controversy – A Documentary History * Robert Hanyok and David Mowry 2008
SIGSALY A History of Secure Voice Coding: Insights Drawn from the Career of One of the Earliest Practitioners of the Art of Speech Coding Joseph P. Campbell, Jr., and Richard A. Dean 2001
SIGSALY SIGSALY Story Patrick Weadon 2000
SIGSALY The Start of the Digital Revolution: SIGSALY – Secure Digital Voice Communications in WWII * J. V. Boone and R. R. Peterson 2000
War in the Pacific The Quiet Heroes of the Southwest Pacific Theater: An Oral History of the Men and Women of CBB and FRUMEL * Sharon A. Maneki 1996
War in the Pacific A Priceless Advantage: U.S. Navy Communications Intelligence and the Battles of Coral Sea, Midway and the Aleutians * Frederick D. Parker 1993
Women Sharing the Burden: Women in Cryptology during WWII * Jennifer Wilcox 1998
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    WHO worked during the war? Find the Personnel section. Also, Joseph R. Desch
    WHAT were their goals? By the Numbers. Also, The US Bombe
    WHY? History of the Bombe Project A contemporary account of the reasons and the plans for their project for the Director of Naval Communications, 1944.
    WHERE was the project: In Dayton, it was in Building 26. In Washington, it was housed at the Naval Communications Annex