During World War II, code breaking would come into its own as one of the most fruitful forms of intelligence that exists. Listening in on enemy conversations provides a verbatim, real-time way to know what that enemy is thinking and doing and arguing about and worrying over and planning. It provides information on strategy, troop movements, shipping itineraries, political alliances, battlefield casualties, pending attacks, and supply needs. The code breakers of World War II advanced what is known as signals intelligence—reading the coded transmissions of enemies, as well as (sometimes) of allies. They laid the groundwork for the now burgeoning field of cybersecurity, which entails protecting one’s data, networks, and communications against enemy attack. They pioneered work that would lead to the modern computing industry. After the war, the U.S. Army and Navy code-breaking operations merged to become what is now the National Security Agency. It was women who helped found the field of clandestine eavesdropping—much bigger and more controversial now than it was then—and it was women in many cases who shaped the early culture of the NSA.
The women also played a central role in shortening the war. Code breaking was crucial to Allied success in defeating Japan, both at sea and during the bloody amphibious assaults on Pacific islands against a foe that was dug in, literally—the cave fighting toward the end of the war was terrible, as were kamikaze attacks and other suicide missions—and willing to fight to the death. And in the all-important Atlantic theater, U.S. and British penetration of the Nazi Enigma cipher that German admiral Karl Dönitz used to direct his U-boat commanders helped bring about the total elimination of the Nazi submarine threat.
The chain of events that led to the women’s recruitment was a long one, but a signal moment occurred in September 1941, when U.S. Navy rear admiral Leigh Noyes wrote a letter to Ada Comstock, the president of Radcliffe College, the women’s counterpart to Harvard. For more than a year the Navy had been quietly recruiting male intelligence officers from elite colleges and universities, and now it was embarking on the same experiment with women. Noyes wanted to know whether Comstock would identify a group of Radcliffe students to be trained in cryptanalysis. He confided that the Navy was looking for “bright, close-mouthed native students”—that is, high-achieving women who had the sense and ability to keep a secret and who had been born in the United States and were free of close ties with other nations.
“Evidence of a flair for languages or for mathematics could be advantageous,” Noyes said, adding that “any intense sociological quirks would, of course, be undesirable.” Without stating what such “quirks” might be, the admiral suggested that a handful of promising seniors could enroll in a training course the Navy had developed.
“In the event of total war,” Noyes told her, “women will be needed for this work, and they can do it probably better than men.”
Ada Comstock was happy to comply. “It interests me very much and I should like to take whatever steps would be thought serviceable,” she promptly wrote to her friend Donald Menzel, an astronomy professor at Harvard who was serving as a point person for the broader naval recruiting effort. Astronomy is a mathematical science and a naval one—for centuries, navigation was done using the position of the sun and the stars—and many of the instructors who taught the secret course would come from the field.
At the Navy’s request, Comstock also approached leaders of other women’s schools. These deans and presidents were devoted to the cause of educating women and eager to defend liberty and freedom of thought against fascism and totalitarian belief systems. They also were keen to develop career opportunities for their students. The leaders savvily perceived that war might open up fields—and spots in graduate schools—that up to now had been closed to women. Even before Comstock received the Navy’s letter, many of the leaders had been strategizing over how they could provide what Virginia Gildersleeve, dean of Barnard College, called “trained brains” to a war effort that would depend on advances in science and math.
The women’s college leaders met at Mount Holyoke on October 31 and November 1, 1941, with representatives from Barnard, Bryn Mawr, Vassar, Wellesley, Radcliffe, Smith, and Mount Holyoke attending. Comstock told them about the Navy’s request and said Radcliffe would participate. She distributed some materials the Navy had developed: a “Guide for Instructors” and an “Introduction to Students.” The idea was that selected students would take the course during the remainder of their senior year, then go to work for the Navy, in Washington, as civilians. The “Guide for Instructors” assured them that no prior experience was necessary and that they would receive a “gouge,” or answers to the problems. The instructors would be given a few texts to jump-start their own education, including a work called Treatise on Cryptography, another titled Notes on Communications Security, and a pamphlet called The Contributions of the Cryptographic Bureaus in the World War—meaning World War I, the so-called war to end all wars.
The result was the wave of secret letters that appeared in college mailboxes in the fall of 1941, summoning surprised young women to secret meetings. Most were in the top 10 percent of their class, selected based on academic performance as well as character and loyalty and grit.