In 1943, the U.S. Navy began sending groups of WAVES by train from Washington, DC, to Dayton, Ohio, to work on a top secret project.
Due to the highly secretive nature of their assignment, the WAVES were not told where they were going or what they would be doing, only that they were headed “west.” Some thought they were going to California and were surprised to arrive in Dayton several hours later.
From Dayton’s Union Station, they were transported by bus to a hillside reserve dotted with cabins and maple trees in the hills a few miles outside of town. They were issued linens and pillows and directed to stow their personal items in the cabins, which would become their home for the next year or so. This 30-acre reserve, called Sugar Camp, was owned by the National Cash Register (NCR) Company.
What the WAVES didn’t learn until years later is that they were there to help build the U.S. Navy’s N-530 Cryptanalytic Bombe, a 5,000-pound electromechanical machine designed to help Navy codebreakers crack the German navy’s Enigma cipher (code-named Shark by the Allies), which utilized an encryption machine that combined the settings of four rotors and a plug board to encode messages.
To decipher an Enigma message, a recipient needed an Enigma machine (or replica) and knowledge of the original settings and rotor starting positions to decipher the message. The Bombe searched all the Enigma rotor settings that allowed the cipher to match the assumed plain text and discarded those that were incorrect.
Since the British already had a Bombe machine and Enigma decryption materials, they had taken the lead on Enigma codebreaking efforts and had been successfully decrypting the German navy’s three-rotor Enigma communications since June 1941. This gave them access to German signals intelligence (which they called Ultra for “Ultra Top Secret”). Ultra intelligence had been vital to the Allies in the Battle of the Atlantic because it provided them with knowledge of U-boat locations. The British lost access to Ultra in February 1942 when the German navy switched to the four-rotor Enigma cipher. The British Bombe machine could not compute rapidly enough to attack the four-rotor Enigma cipher.
After the critical Allied shipping convoy losses during the first eight months of 1942, the U.S. Navy launched its own Bombe project that September. The service’s cryptologic branch (OP-20-G) contracted with the NCR company in Dayton, Ohio, to use their plant and employ their chief of electrical research, Joseph Desch, to manufacture and design the decryption machine.
In the spring of 1943, Desch and his team of contracted Navy engineers had just finished two prototype Bombe machines when the first WAVES arrived. Just out of boot camp, the WAVES marched to work at the NCR campus to maintain discipline and esprit de corps. They’d already passed their background checks prior to leaving the Naval Communication Annex Washington, DC, and had attended security briefings, in which they were ordered to not talk to anyone about the project. If asked by Dayton townspeople what they were working on, they were told to say they were learning how to use special accounting machines.
The WAVES worked at the Naval Computing Machine Laboratory (former Building 26 on the NCR company campus), where they wired and soldered parts for the Bombe machine. Soldering had not yet been automated, so it had to be done by hand. Following wiring diagrams, the women wrapped wires around prongs and soldered the tip of each wire to the contact point on a commutator wheel. They wired tens of thousands of rotors for the initial Bombe machines and additional rotors for replacement wheels. Those that were not able to master the intricate wiring of the commutator wheels assembled wire harnesses for the Bombe machine’s circuitry.
The engineers overseeing the assembly organized the WAVES’ workloads so that each woman saw only one component of the machine and never the final product. The women worked in small groups in separate locked rooms guarded by marines. While one group might be soldering wiring to one side of a commutator wheel, another group might be wiring the other side of the wheel.
The women suspected that the wheels would be attached to some sort of machine, but they didn’t know what the machine did—and they weren’t allowed to talk about it, even with each other. One of the WAVES said later (after the project was declassified) that she couldn’t help but notice that the wheels they were wiring and assembling had 26 wires and had 26 numbers on them (zero to 25), just like the letters of the alphabet.
What the WAVES didn’t know was that the complete machine was being assembled on a separate floor in the same building by other naval enlisted personnel.
“We never talked about our work or asked about other activities being carried out in other parts of Building 26,” said Sue Unger Eskey, quoted in The Secret in Building 26: The Untold Story of the American Women Codebreakers of World War II. “We had no knowledge that the Bombe was being conceived and built directly over our heads on Floor 2.”
The machines would eventually be sent to the Naval Communication Annex in Washington using the railway spur line that was located next to Building 26. However, the Navy was still building the infrastructure to house the heavy machines at the annex. In the meantime, completed machines lined the hallways at the Dayton facility.
During that summer of 1943, the Navy set up a secure line between the Naval Communication Annex and Dayton so that the codebreakers in Washington could utilize the machines for their work while they waited for the Navy to finish construction at the annex. Codebreakers in Washington created set-up instructions for the Navy Bombe machine, which they sent to Dayton. These initial settings were called a “menu.” A menu was created through a complex process in which codebreakers lined up the assumed text of a message in a way that corresponded to the Enigma cipher. The operators then set the dials and rotors of the machine according to the cryptanalyst’s menu, and it began to search for settings—usually taking only 20 minutes. Once the machine had finished searching, it produced a printout of the settings. A supervisor tested the settings with a small machine called an M-9. The M-9 could verify results like an Enigma machine, and since the Bombe machine could not produce all the Enigma plug board settings, the supervisor had to do that using the M-9. The verified results were logged and then sent by pneumatic tube to cryptanalysts. The cryptanalysts used another machine called the M-8, which decrypted the message and printed it out in German. Linguists then translated the German messages into English for use by military commanders.
In September of 1943, the Navy began to ship the machines at a rate of four per week to Washington under armed guard. Upon arrival at Washington’s Union Station, they were transported via truck to the Naval Communication Annex. There, after setup, another group of WAVES would run the Bombe machines around the clock, testing Enigma keys. Some of the WAVES working on the Dayton project were moved from manufacturing to the communication annex, where they were taught codebreaking. That is where they saw the fully assembled Bombe machines for the first time.
The Dayton WAVES and other naval personnel built 121 Bombes. They were 50 percent faster than their British counterparts. By the end of 1944, American codebreakers were able to decrypt Shark messages within 12 hours. In May 1944, the Allies sank more than half of the operating U-boats, destroying them at a rate faster than they could be replaced. Also, the losses of Allied merchant shipping remained low that year, with almost no casualties in the Atlantic.
By 1945, 600 WAVES and 200 sailors had worked on the classified project. For 50 years, the WAVES that worked on the Bombe project kept the project secret. It was finally declassified in the 1990s.
Further Reading
Bailey, Ronald H. “Secret Doings in Dayton.” World War II, 30, no. 5 (January/February 2016): 62
Blair, Clay. Hitler’s U-Boat War, Vol. I: The Hunters, 1939–1942. New York: Random House, 1996.
“Dayton Codebreakers.” Deborah Anderson, 10 April 2024. https://daytoncodebreakers.org
DeBrosse, Jim, and Colin Burke. The Secret in Building 26: The Untold Story of America’s Ultra War against the U-boat Enigma Codes. New York: Random House, 2004.
Lee, John A. N., Colin Burke, and Deborah Anderson. “The U.S. Bombes, NCR, Joseph Desch, and 600 WAVES: The First Reunion of the U.S. Naval Computing Machine Laboratory.” IEEE Annals of the History of Computing 22, no. 3 (August 2000): https://www.researchgate.net/publication/3330753 .
Lycett, Andrew. “Breaking Germany’s Enigma Code.” BBC Online (archive). 17 February 2011: https://www.bbc.co.uk/history/worldwars/wwtwo/enigma_01.shtml.
Mundy, Liza. Code Girls: The Untold Story of the American Women Codebreakers of World War II. New York: Hachette Books, 2017.
National Archives at College Park, College Park, MD, Personnel Numbers, “Personnel at U.S. Naval Computer Machine Laboratory, Dayton, Ohio.” 28 June 1945. Record Group 38 (Crane Library), Box 74 National Archives and Records, cited in Dayton Codebreakers | A story so important it was secret for 50 years.
Russell, Jerry. “Ultra and the Campaign against the U-Boats in World War II U.S. Army War College/National Security Agency, 20 May 1980. ” Naval History and Heritage Command: https://www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/u/current-doctrine-submarines-usf-25-a.html
Sears, David. “The Navy’s ‘Imitation Game.’” Naval History, August 2016: https://www.usni.org/magazines/naval-history-magazine/2016/august/navys-imitation-game
Wilcox, Jennifer. Solving the Enigma: History of the Cryptanalytic Bombe. Center for Cryptologic History. Fort Meade, MD: United States National Security Agency/Center for Cryptologic History, 2015: https://media.defense.gov/2022/Sep/29/2003087366/-1/-1/0/SOLVING%20THE%20ENIGMA%20-%20HISTORY%20OF%20THE%20CRYPTANALYTIC%20BOMBE.PDF.