Officials at the code-breaking compound in Washington were tasked with coordinating the bombe construction project, and what this meant, for top naval officers, was much running back and forth between Washington and Ohio. In Dayton, Building 26 was modified and renamed the U.S. Naval Computing Machine Laboratory. Meanwhile, the Naval Annex at the former Mount Vernon Seminary set up OP-20-G-M, a top secret “research” group of engineers and mathematicians, to work with Desch. First, though, they decided that Agnes Driscoll had to be neutralized. On January 31, 1943, a unit diary included a brief and rather merciless notation that on that day “Mrs. Driscoll, Mrs. Clark, Mrs. Talley, Mrs. Hamilton transferred to Japanese N.A.T. Project.” (That was the naval attaché machine, which Frank Raven ultimately broke.) Lieutenant Commander Howard Engstrom, a mathematics professor from Yale, took over the Enigma project, aided by a formidable group of intellects that included John Howard, an engineer from MIT; Donald Menzel, the Harvard astronomer; Marshall Hall, a mathematician from Yale; and others.
Including women. A number of the research department’s mathematical staff were female. Like everybody else, the Navy was eager to locate women capable of doing higher math—the very field that women long had been discouraged from entering—and the Naval Annex put out the word to boot-camp evaluators, asking them to be on the lookout for enlisted women who scored high on the math aptitude test. These women had not enjoyed anything like the same educational opportunities the men had, nor the chance to embark on distinguished careers as engineers and academic mathematicians. They did, however, have the aptitude, the desire, and the ability. Many found, in the bombe project, the kind of statistical and probability work that they had been looking for all their lives.
One such woman was Louise Pearsall, a twenty-two-year-old from Elgin, Illinois, an industrial suburb about forty miles outside of Chicago. Before the war, her mother had been a member of the America First movement—an isolationist, along with the rest of her suburban bridge club—but all card-table chatter about isolationism ceased on December 7, 1941, when two Elgin boys went down on the USS Arizona. Louise, the oldest of four, attended high school on scholarship at the private Elgin Academy. She aspired to become an actuary, hoping to find work with an insurance company, making statistical projections about risks. It was a modest enough ambition, were it not for the fact that actuarial math—as she often was reminded by deans and potential employers—was a man’s field.
Even so, Louise went to the University of Iowa, where she was the only woman in many of her math classes—the chalk-covered little calculus professor used to stare at her as he paced the room, disconcerted by her presence—and performed well. But she left after two years because her father struggled to afford the tuition and didn’t think it would pay off with a job. Louise enlisted in the WAVES, expecting to be made an officer, but the first class of female officers filled so quickly that she and some other educated women—“real intelligent gals,” as she recalled them—went in as ordinary seamen, so as to get into war service as soon as they could.
At specialized training camp in Madison, Wisconsin, Louise took classes in physics, Morse code, and radio operation, where she was held up from graduating because of an audio dyslexia that made it hard for her to master receiving Morse. The timing was perfect. Instead of becoming a radio operator, she was rerouted to the Enigma project. In March 1943 she got orders to travel to Washington, where, at the Naval Annex, she underwent more tests and interviews and found herself assigned to work for MIT’s John Howard. As the design for the new high-speed bombes was refined, it was Louise’s job to sit at a desk and do what the bombe would ultimately do faster: test Enigma key settings. She worked on permutations, figuring out, if X became M, and T became P, what was the mathematical formula that would take a letter through the right sequence. It was intense work, utterly absorbing.
“That,” she told her daughter later, “was where I should have been all my life.”
To come up with an Enigma key setting, the naval team had to understand more than math. They had to understand the nature of the messages that German U-boat commanders sent. And the commanders sent a great many messages, much as the Japanese did, and for the same reasons. German Admiral D?nitz was a micromanager who insisted upon total command and control of his U-boat fleet. Submarines were obliged to constantly communicate with headquarters, providing updates that enabled D?nitz to make tactical decisions and issue orders. Since the boats were often thousands of miles from Germany, doing so entailed sending messages over high-frequency circuits that could cover long distances. This—as with the Japanese in the Pacific—opened them up to enemy interception. The wolf-pack tactic, in which many U-boats would be summoned once a convoy was sighted, also meant the subs had to abandon the radio silence normally observed during a group naval operation.
So the Allied mathematicians went about learning German naval greetings, the names of U-boats and commanders, and how German messages tended to be phrased. They knew a short message from D?nitz might include an order to “report your position” or to head for a port on the French coast. Subs often reported location and fuel capacity. All of this helped the code breakers come up with cribs. If they suspected that a line of cipher such as
RWIVTYRESXBFOGKUHQBAISE
represented the German phrase “weather forecast Biscay”:
WETTERVORHERSAGEBISKAYA
they would line up the two lines of type, write numbers over or under them,
1 2 3 4 5 6 7 and so on
and look for “loops,” places where one letter turned into another, and then that second letter turned into another. In the above example, they would see that E paired with T at position 5, T with V at 4, V with R at 7, R with W at 1, and W with E at 2, closing the loop. When the bombes were up and running, they would be able to program these into the bombe machine, which sought a setting where all these loops would happen. Since they didn’t yet have machines, Louise herself was the bombe, sitting in a small room with a tiny team of colleagues, “working in an office on figures,” as she later put it. “We had no equipment. We didn’t have anything, really, to do anything big with. We were just getting started.”
The Enigma had a few weaknesses that helped them. No letter could be enciphered to itself—that is, B would never become B. The machine had a reciprocal quality, meaning that if D became B on a certain key setting, then B became D. These factors limited the encipherments, but only somewhat; the possibilities still ran into the billions. Sometimes the team would get a key setting for a couple of days; sometimes they could not get a setting at all. There would be moments of clarity and long periods of darkness. The inconsistency of their work—and the helplessness when they could not recover a key setting—was dreadful. Ann White, from Wellesley, was working in the unit that translated broken Enigma messages from German to English. She always remembered one terrible night when a high-ranking naval officer came in, gave them a message, and begged, “Can’t you give us any clues?”
As the summer of 1943 approached, John Howard told Louise Pearsall she needed to learn how to shoot a pistol. Some members of the mathematical research unit were relocating to Dayton, and she was one of those picked to go. She began doing target practice with a.38. In early May she and four other women, with about the same number of men, got their guns, boarded the train, and headed west to Dayton. Soon they too found themselves billeted at Sugar Camp. Unlike their bunkmates, these women knew why they were there. They were going to help make the bombes work.