Code Girls

The True Story of the American Women Who Secretly Broke Codes in World War II (Young Readers Edition)


By Liza Mundy

Read by Christine Lakin

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In the tradition of Hidden Figures and The Girls of Atomic City, Code Girls is the amazing true story of the young American women who cracked German and Japanese military codes during World War II.

More than ten thousand women served as codebreakers during World War II, recruited by the U.S. Army and Navy. While their brothers and boyfriends took up arms, these women moved to the nation’s capital to learn the top secret art of code breaking.

Through their work, the “code girls” helped save countless lives and were vital in ending the war. But due to the top secret nature of their accomplishments, these women have never been able to talk about their story–until now.

Through dazzling research and countless interviews with the surviving code girls, Liza Mundy brings their story to life with zeal, grace, and passion. Abridged and adapted for a middle grade audience, Code Girls brings this important story to young readers for the first time, showcasing this vital story of American courage, service, and scientific accomplishment.


Codes and Ciphers

cipher: A secret message system in which a single letter or number is replaced by another single letter or number

code: A secret message system in which an entire word or phrase is replaced by another word, a series of letters, or a string of numbers known as a “code group”

cryptanalysis: The art and science of breaking codes and ciphers

cryptography: The art and science of making codes and ciphers

cryptology: Both making and breaking codes and ciphers

A World at War

During World War II, the United States and its allies (the Allied powers) fought against the Axis powers.



Great Britain

Soviet Union

United States






The Secret Letters

December 7, 1941

The planes looked like distant pinpoints at first. No one took them seriously. An Army officer said the blips on the radar screens must be a group of American bombers arriving from California. A Navy commander, peering out his office window, saw a plane going into a dive and thought it was a reckless American pilot. “Get that fellow’s number,” he told his junior officer. “I want to report him.” Then a dark shape fell out of the plane and whistled downward.

Just minutes before eight a.m., the planes burst into view. Nearly two hundred Japanese fighters and bombers filled the sky like a fast-moving thundercloud. Finally, the people looking at them understood.

Below the planes lay Pearl Harbor’s Battleship Row, a line of American warships. They were completely unprotected. Almost one hundred ships, more than half of the entire US Pacific Fleet, dotted the harbor. In nearby airfields, American planes sat wingtip to wingtip like fat targets.

One of the bombs found the USS Arizona and pierced the battleship’s forward deck. It set off a store of gunpowder to create a giant fireball. The ship was hit over and over. It rose out of the water, cracked, and sank. Other bombs and torpedoes found the California, the Oklahoma, the West Virginia, the Tennessee, the Nevada, the Maryland, and the Pennsylvania.

A second wave of planes arrived an hour after the first. They dove, peeled off, and came back again and again. Ships and buildings were hit. Three battleships sank; another capsized. More than two thousand men were killed. Nearly half of the men who died were on the Arizona, including twenty-three pairs of brothers.

The American planes were destroyed.

News of the Pearl Harbor attack raced through the country. There were telephone calls and radio broadcasts. Newspapers printed special editions and people ran shouting along the street. Congress declared war on Japan the next day. Germany—Japan’s ally—declared war on the United States three days later. Men flooded Army and Navy recruiting stations in the weeks that followed. Every American felt affected by the tragedy.

War had been coming to America for more than a year. Even so, it was unthinkable that Japan would attack without warning. It was equally unthinkable that America’s leaders had not seen Pearl Harbor coming.

These leaders knew that a failure on the scale of Pearl Harbor must not happen again. The country was fighting a global war against enemies who had been getting ready for years. Intelligence—the collection of information for military and political use—was more important than ever, yet extremely hard to come by. The Navy had a small, disorganized intelligence group. The Army had its own small operation. The United States had barely any spies abroad.

A first-rate code-breaking operation was necessary if America had any hope of winning the war.

And so the secret letters began going out.

Months before the attack on Pearl Harbor, the US Navy realized that it was way behind other countries in gathering intelligence. So a handful of letters appeared in college mailboxes as early as November 1941. Ann White, a senior at Wellesley College in Massachusetts, received hers on a fall afternoon.

She was invited to a private interview with Helen Dodson, a professor in Wellesley’s Astronomy Department. Ann, a German major, was worried she might have to take an astronomy course in order to graduate. But she found that Helen Dodson had only two questions for her.

Did Ann White like crossword puzzles, and was she engaged to be married?

In all, more than twenty Wellesley seniors received secret invitations and gave the same replies. Yes, they liked crossword puzzles, and no, they were not engaged.

At Bryn Mawr, Mount Holyoke, Barnard, and Radcliffe, the letters went out to students from professors who were working with the Navy. The schools were founded to educate women at a time when most colleges would not admit them, when many people considered girls to be unworthy of higher education. But with men needed to fight, opinions changed.

Educated women were wanted. Urgently.

On many of these campuses, war felt particularly close. In the cold waters of the North Atlantic, German submarines preyed on US ships transporting food and supplies to England. In the terrible winter of 1942 students were rolling bandages, sewing blackout curtains, taking first aid courses, learning to do plane spotting, and sending bundles to Britain. Dorm rooms grew cold from lack of fuel.

The female students were called to secret meetings where they learned that the US Navy was inviting them to embark on a field called “cryptanalysis.” That meant they would be analyzing and breaking the secret codes America’s enemies used to communicate top secret information. The United States wanted to be able to read those messages. If the women passed a course in code breaking, they would go to Washington, DC, after graduation to take jobs with the Navy as civilians.

The women couldn’t tell anybody what they were doing: not their friends, not their parents, not their roommates. They couldn’t let news of their training leak, not even to brothers or boyfriends in the military. If asked, they could say they were studying communications.

And so the young women mastered methods of disguising letters and creating ciphers. They hid homework under desk blotters and strung quilts across their rooms so that roommates couldn’t see what they were up to. Every week, their answers to a series of problem sets were sent to Washington.

The invitations spread beyond the Northeast to Goucher, a four-year women’s college in Baltimore, Maryland. In a locked room at the top of Goucher Hall, an English professor and a Navy officer taught the secret course to the college’s top senior girls.

One of the most well-liked students in the Goucher class of 1942 was Frances Steen. Fran was a biology major and the granddaughter of a shipping captain who ferried grain between the United States and his native Norway, which now was under Nazi occupation. Her father ran a grain warehouse at the Baltimore dock. Her brother, Egil, had graduated from the US Naval Academy. By the time Fran got her own secret letter, Egil’s ship was in the North Atlantic. The Steen family was doing everything they could to support the war effort. Fran’s mother was saving grease from bacon and giving away pots and pans to be made into tanks and guns.

Now there was something else the Steen family could contribute to the war effort: Fran.

As war engulfed the nation, the secret letters continued to go out. Code breaking was key to saving American lives.

At Vassar College in Poughkeepsie, New York, Edith Reynolds received a letter inviting her to appear in a room in the library. She stood, dazzled, with a few chosen classmates as a Navy captain covered in gold braid walked in. “Your country needs you, young ladies,” he told them.

By that time, German U-boats had attacked shipping up and down the Atlantic coast. On the New Jersey shore, where Edith’s family spent summers, bits of shipwreck washed up and they could hear guns booming. It did not seem out of the question that Japan and Germany would invade the United States.

The US Army, meanwhile, needed its own team of code breakers and set out to recruit smart young women. At first, the Army approached some of the same colleges the Navy did. Like the Navy, the Army wanted women who studied foreign languages as well as science and math. In the United States, in the 1940s, there was only one job available to a woman with such a fine education: schoolteacher.

And so—when the Navy objected that the Army was trying to steal “their” girls—the Army sent recruiters to teaching colleges. It was hard to find female students taking high-level math classes. Math was not a subject women were encouraged to study or to teach. In certain parts of the country there were no female math teachers at all. Those students who studied math because it was a passion jumped at the chance to serve their country in this way.

The Army needed more code breakers, and then more still. Going to teaching colleges wasn’t enough. So it went looking for female schoolteachers interested in a new line of work. The Army sent handsome officers to small towns, remote cities, and farm communities, seeking women willing to move to Washington to serve the war effort, women who could “keep their lips zipped.”

And so it was that on a Saturday in September 1943, a young schoolteacher named Dot Braden approached a pair of recruiters in the Virginian Hotel. Dot was twenty-three years old, dark-haired, adventurous, and confident. She was a 1942 graduate of Randolph-Macon Woman’s College, where she studied French, Latin, and physics, and had spent one year teaching at a public high school. The eldest of four children, with two brothers serving in the Army, Dot needed to earn her own living and help support her mother.

Without knowing what she was applying for, Dot Braden filled out an application for a job with the War Department. A few weeks later, she found herself on a train headed to Washington, DC, with excitement in the pit of her stomach, very little money in her pocketbook, and not the faintest idea what she had been hired to do.

More than ten thousand women traveled to Washington, DC, to lend their minds to the war effort. The US military’s decision to tap young women—and the women’s willingness to accept the job—was a chief reason why America was able to build a code-breaking operation practically overnight. The fact that women were responsible for some of the most significant code-breaking triumphs of the war—and indeed, for shortening the war itself—was one of the best-kept secrets of the conflict.

The chain of events that led the Navy and the Army to recruit women is a long one. In September 1941, the US Navy asked Ada Comstock, the president of Radcliffe College, to identify a group of students to be trained in cryptanalysis.

The Navy was looking for bright women who had the ability to keep a secret, were born in the United States, were free of close ties with other nations, and had a flair for mathematics and languages. The Navy was also clear about the kind of women they did not want, including communists, pacifists, and anyone from a country or race being persecuted by the Germans, including Poles and Jews.

At the Navy’s request, Comstock also approached leaders of other women’s schools. Representatives from Barnard, Bryn Mawr, Vassar, Wellesley, Radcliffe, Smith, and Mount Holyoke met on October 31 and November 1, 1941. Ada Comstock handed out 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 what was left of their senior year, then go to work for the Navy, in Washington, as civilians.

The wave of secret letters inviting young women to secret meetings followed in the fall of 1941. Most of the women were in the top 10 percent of their class. The women were warned not to say the word “cryptanalysis” outside their classrooms. They were also told not to use the words “intelligence” or “security” to any person outside their study group, so as not to tip off the enemy.

In the late spring of 1942, the first wave of women recruited by the US Navy finished their secret courses and set out for Washington, DC, to start their duties. The women were told that just because they were female, that did not mean they would not be shot if they told anybody what they were doing. If they were asked what they did, they were to say they emptied trash cans and sharpened pencils. People believed them.

During the most violent global conflict that humanity has ever known—a war that cost more money, damaged more property, and took more lives than any war before or since—these women formed the backbone of one of the most successful intelligence efforts in history.

In the packets they opened before arriving in Washington, the women were told that, up to now, cryptanalytic work had been done by men.

“Whether women can take it over successfully,” the Navy letter told them, “remains to be proved.”

The letter added: “We believe you can do it.”

Code breaking was a joint effort. The Americans had to cooperate with England’s older and more sophisticated code-breaking operation, known as Bletchley Park. Thousands of Englishwomen had been hired to work there beginning in 1937, when it seemed as if there might be a second world war. The women operated “bombe” machines. These machines had been built to crack the Enigma ciphers used by the German Navy, Army, Air Force, and security services.

At the beginning, the Allies decided that the British would lead the code-breaking efforts in the war in Europe and the Atlantic. The Americans had the lead responsibility for code breaking in the Pacific.

As the war went on, the United States’ code-breaking operation became central to the European conflict. More and more of the employees of both operations were women, as men shipped out to the hot, dry sands of North Africa, to Italian mountain ranges and snowy European forests, to the decks of Pacific aircraft carriers, to the beaches of Iwo Jima.

It was easy for the women’s contribution to be overlooked. The women took their secrecy oath seriously. They weren’t among the top brass and didn’t write the histories afterward. And yet women were instrumental at every stage. They ran complex code-breaking machines. They built libraries and information sections. They worked as translators.

Women were often put in charge of “minor” systems—weather codes, for instance—that turned out to be key when major systems could not be read. And a number of mostly female teams broke major code systems.

It was a complicated position. Women were brought into the workforce to free up men for military service. As a result, men who had been doing office work were able to ship out to war. So women were welcome, but also resented. They themselves were trying to protect the men whose lives their arrival put in danger. They all had brothers, friends, and fiancés serving in the war.

In 1942, only about 4 percent of American women had completed four years of college. In part this was because women were denied admission to so many schools. Coeducational colleges capped the number of women they would admit. Families were more likely to pay a son’s tuition than a daughter’s. For a woman, a degree did not carry the same promise of future earnings that it did for a man, and many families did not consider it worthwhile for a daughter to attend college.

Those who did go to college were unusually motivated. Some came from families who valued learning for its own sake. Other families viewed college as a way for a woman to meet eligible college men at dances and mixers. Sometimes the women came from immigrant families—German, French, Italian—where having a daughter in college was a way of Americanizing the family as quickly as possible. Sometimes, a girl was so intellectually curious that there was no way to keep her away from college. It was not easy being a smart girl in the 1940s. People thought you were annoying.

What is interesting about this generation of women is that they did understand that at some point they might have to work for pay. Raised during the Great Depression, they knew they might have to support themselves no matter how “good” a marriage they did or did not make. And some women went to college because they planned to compete for the few spots in law or medical schools that were available to them.

In the 1940s, there were newspaper want ads that read “Male Help Wanted” and others that read “Female Help Wanted.” For educated women, there was a tiny universe of jobs to be had, and these always paid less than men’s jobs did. But it turned out that the very jobs women had been hired to do were often the ones that taught them the best skills for code-breaking work. Schoolteaching was perhaps the most important of these.

There were other women’s jobs that turned out to be useful. Librarians were recruited to make sense of piled-up tangles of coded messages. Secretaries were good at filing and record keeping. Running office machines was a woman’s occupation, and thousands were now needed to run the IBM machines. Musical talent is an indicator of code-breaking prowess, so all that piano practicing that girls did paid off. Telephone switchboard operators were not scared off by the most complex machines.

It was a rare moment in American history when educated women were not only wanted but competed for in the workforce. Up to now, many college leaders had hesitated to encourage women to major in math or science, because jobs for women in those fields were nearly impossible to get. Soon after Pearl Harbor, however, that changed. The men were gone but the jobs they left behind still had to be done. Female chemists, mathematicians, engineers, and designers were needed. The different branches of the military were competing with private companies and with one another to win their services.

This was seen as temporary. Sexism persisted: Educators worried that they might encourage women to pursue math and science only to see them left high and dry. One electrical company asked for twenty female engineers from Goucher, with the added request, “Select beautiful ones for we don’t want them on our hands after the war.”

The Axis powers didn’t employ women the same way the Allies did. Japan and Germany were highly traditional cultures, and women were not asked to perform wartime military service. They rarely broke codes or did other high-level jobs, particularly in Japan.

The United States hired women by the thousands. On the eve of Pearl Harbor, the Army had 181 people working in a small, highly secret code-breaking office. By 1945 nearly 8,000 people would be working for the Army’s massive code-breaking operation in Arlington, Virginia, with another 2,500 working in the field. Of the entire group, some 7,000—nearly 70 percent—were female.

Similarly, at the war’s outset the US Navy had just a few hundred code breakers. By 1945 there were about 5,000 naval code breakers in Washington and about the same number serving overseas. At least 80 percent of the code breakers in Washington—some 4,000—were female.

Altogether, out of about 20,000 total American code breakers during the war, some 11,000 were women.

There are of course many reasons why the Allies succeeded in World War II, but the employment of women was one of these factors. It wasn’t just that the women freed the men to fight. Women were active war agents. Through their brainwork, the women had an impact on the fighting.

After the war, the Joint Committee on the Investigation of the Pearl Harbor Attack noted that Army and Navy intelligence was “some of the finest intelligence available in our history” and that it “contributed enormously to the defeat of the enemy, greatly shortening the war, and saving many thousands of lives.”

The fact that more than half of these code breakers were women was never mentioned.

World War I Code Breaking: A Matter of Life and Death

In its secret letters, the US Navy told its female recruits that they were embarking on work that had always been done by men. That was not completely true. Even before World War II there were some very important female pioneers in the world of cryptanalysis. Their breakthroughs became even more important after the war began.

Code breaking often makes advances during times of war, when it becomes a matter of life and death. But cryptanalysis was not a job that career military men wanted. And so wartime, exactly when code breaking was most needed, was exactly when women were invited to pinch-hit.

William and Elizebeth Friedman were a married couple with a fascination for code making and code breaking. After the United States entered World War I, William was sent to France to develop codes for front-line use, while Elizebeth oversaw a department that handled all the code and cipher work for the government in Washington.

When World War I ended, the Army hired both Friedmans, offering William a salary of $3,000 and Elizebeth a position at half that, $1,520. William worked for the Army for the next thirty years, while Elizebeth made headlines as a special agent for the Department of Justice in the 1930s working on smuggling and organized crime cases.

The US Navy, meanwhile, was developing its own female secret weapon as part of a code-breaking operation separate from the Army’s. Agnes Meyer (later Agnes Meyer Driscoll), a brilliant young teacher who would become one of the greatest cryptanalysts of all time, enlisted in the naval reserves when the United States declared war on Germany in 1917. The Navy put the former math teacher to work encoding America’s messages. She got her start making codes, which is the best possible training for learning how to break them.

Agnes would go on to train nearly all of the male naval code breakers who became famous for their World War II exploits.


The Most Difficult Problem

September 1940

The United States began beefing up its code-breaking operations months before the attack on Pearl Harbor. By September 1940, Germany had defeated Poland and Czechoslovakia. The Nazi war machine had overrun Norway and Denmark, defeated Belgium and so many others, and proceeded to march into Paris. Meanwhile, Japan was shouldering its way through China and around the Pacific. It was clear enough that sooner or later the United States would formally enter what was shaping up to be a second world war.

While the Navy tackled Japanese naval ciphers in offices nearby, the Army code breakers were attempting to penetrate one of the most complicated code systems they had ever come up against.

At the center of the Army’s operation was William Friedman. Originally hired to develop codes for the US Army during World War I, Friedman had learned to break codes better than almost anybody in the world.

Friedman, now in his late forties, was a legend among the still-small global community of people involved in the making and breaking of codes and ciphers. In 1930 Friedman’s bosses had given him funds to hire three young mathematicians: Frank Rowlett, a southerner who was teaching in Rocky Mount, Virginia, and Abraham Sinkov and Solomon Kullback, friends who had attended high school and City College of New York together. Along with John Hurt, a Virginian who could translate deciphered Japanese messages into English, the men had spent nearly a decade studying Friedman’s methods of “attacking” codes and ciphers.

As the staff expanded, Friedman had begun hiring women. In the 1930s President Franklin Roosevelt’s New Deal programs—programs designed to lift the country out of the Great Depression—had begun drawing women workers to Washington. Friedman also liked working with intelligent women, as evidenced by his own marriage to Elizebeth.


  • Praise for Code Girls: Young Readers Edition:

"The book reads like a movie script, with interesting characters and non-stop action bringing to life the history these women were making and living...excellent."—School Library Connection
  • "Mundy highlights the lives of the many brilliant women who secretly served the code breaking mission against Nazi Germany and Imperial Japan.... A solid resource for younger researchers."—School Library Journal
  • "an entertaining presentation on a fascinating topic"—Kirkus Reviews
  • On Sale
    Oct 2, 2018
    Hachette Audio

    Liza Mundy author photo credit by Nina Subin

    Liza Mundy

    About the Author

    New York Times bestselling author Liza Mundy is a former reporter at The Washington Post and contributes to numerous publications including The Atlantic, TIME, The New York Times, The New Republic, Slate, Mother Jones, Spectator (UK), and The Guardian. She is a frequent commentator on countless prominent national television, radio, and online news outlets.

    Learn more about this author