Code Girls

Code Girls Plot Summary

Introduction

In the early hours of December 7, 1941, as Japanese planes descended upon Pearl Harbor, a small group of women in Washington D.C. already knew war was imminent. For months, they had been deciphering Japanese diplomatic messages, piecing together the puzzle of enemy intentions. These women—college graduates, schoolteachers, and mathematicians—formed the vanguard of what would become one of history's most remarkable intelligence operations. Their story remained classified for decades, hidden behind security oaths and government secrecy. The remarkable tale of female codebreakers reveals how women transformed modern warfare through intellectual rather than physical combat. Working in converted girls' schools and makeshift facilities, they broke seemingly impenetrable Japanese and German encryption systems, providing intelligence that shortened the war by years and saved countless lives. Their achievements challenge conventional narratives about women's contributions during World War II, demonstrating that beyond factories and nursing stations, women played decisive roles in the most sophisticated intelligence operations of the conflict. This hidden history illuminates not just the evolution of cryptanalysis but also the untold story of how talent and patriotism transcended gender barriers during humanity's greatest crisis.

Chapter 1: Early Pioneers: Women Enter Cryptanalysis (1916-1940)

The story of female codebreakers begins not with World War II but in the unusual setting of Riverbank Laboratories in Geneva, Illinois. In 1916, a young woman named Elizebeth Smith visited Chicago's Newberry Library seeking employment related to literature. Instead, she encountered eccentric millionaire George Fabyan, who recruited her to work at his private research facility. There, amid peculiar surroundings that included a Roman bath and a pet chimpanzee, Elizebeth discovered an unexpected talent for breaking codes. At Riverbank, Elizebeth met William Friedman, a geneticist who would become her husband and partner in cryptanalysis. When America entered World War I, the Friedmans found themselves training military officers and solving actual wartime messages, as the U.S. government had no formal code-breaking operation. After the war, William joined the Army's Signal Intelligence Service, while Elizebeth established herself breaking codes for the Coast Guard during Prohibition, helping capture rum-runners and gangsters. Meanwhile, Agnes Meyer Driscoll, another pioneering woman with degrees in mathematics, music, physics, and languages, joined the U.S. Navy as a "yeomanette" during World War I and later became their premier cryptanalyst, spending decades breaking Japanese naval codes. These women thrived in cryptanalysis partly because the field lacked established gender barriers. Unlike medicine or law, code-breaking was so new that professional gatekeeping hadn't yet developed. Both Elizebeth Friedman and Agnes Driscoll trained men who would later become famous for wartime achievements, establishing precedents that made it natural for military leaders to turn to women when World War II created urgent demand for cryptanalysts. By the late 1930s, William Friedman had begun expanding his small Army code-breaking unit, hiring not only male mathematicians but also women like Wilma Berryman, who had been inspired by Elizebeth Friedman's example. The pioneering work of these early female cryptanalysts laid crucial groundwork for what would become one of history's most successful intelligence operations. They developed techniques for attacking complex cipher systems, trained the first generation of American cryptanalysts, and demonstrated that women could excel in this intellectually demanding field. Their legacy would soon expand beyond anything they could have imagined, as thousands of young American women answered their country's call during World War II, breaking enemy codes and helping secure Allied victory. The significance of these early pioneers extends far beyond their immediate contributions. They established cryptanalysis as a field where merit mattered more than gender, creating opportunities that would eventually allow women to comprise more than 70% of America's wartime code-breaking force. As war clouds gathered over Europe and Asia in the late 1930s, the foundation these women had built would prove crucial to America's intelligence capabilities in the coming conflict.

Chapter 2: Wartime Recruitment: Mobilizing Female Intellect (1941-1942)

The Japanese attack on Pearl Harbor in December 1941 transformed America's nascent code-breaking operations from modest efforts into massive enterprises requiring thousands of skilled personnel. With most young men being drafted for combat roles, military leaders faced a critical shortage of analytical talent. Their solution was unprecedented: a systematic recruitment of America's brightest young women. The Navy led the way, sending confidential letters to presidents of elite women's colleges like Wellesley, Smith, and Vassar, requesting their most promising mathematics, physics, and language students for "essential war work." These college women received mysterious invitations to take correspondence courses in cryptanalysis, sworn to secrecy about their studies. Meanwhile, the Army cast a wider net, dispatching recruiters to teachers' colleges across the South, where they found women like Dorothy "Dot" Braden, a schoolteacher from Lynchburg, Virginia. The recruiters were deliberately vague about the nature of the work, sometimes even misleading candidates. Many women were simply told they would be doing "clerical duties" for the War Department, only to discover upon arrival in Washington that they would be breaking enemy codes. The women converged on Washington in 1942, finding themselves assigned to Arlington Hall (a former girls' school requisitioned by the Army) or the Naval Communications Annex (previously Mount Vernon Seminary for women). Their training was minimal—often just a few weeks of instruction before being thrust into actual code-breaking work. They learned specialized terminology and techniques: "stripping" additives from Japanese codes, identifying "cribs" in German messages, analyzing "traffic" patterns. Despite the technical complexity, most adapted quickly, displaying an aptitude that surprised their male supervisors. What made these recruitment efforts remarkable was their focus on intellectual ability rather than social background. While American society remained deeply traditional in most respects, the desperate need for code breakers created unprecedented opportunities for women with analytical minds. College professors identified their most promising students, while Army recruiters sought out women who demonstrated exceptional problem-solving skills regardless of their origins. By mid-1942, hundreds of women had been quietly recruited into America's code-breaking operations, forming the vanguard of what would eventually become a predominantly female workforce. The militarization of women's code-breaking accelerated in July 1942 with the creation of the Women's Reserve of the U.S. Naval Reserve, cleverly acronymed WAVES (Women Accepted for Volunteer Emergency Service). Unlike the Women's Army Auxiliary Corps (WAAC), WAVES were full members of the Naval Reserve, entitled to the same pay as men in equivalent positions. Many civilian women code breakers accepted commissions as WAVES officers, donning smart Mainbocher-designed uniforms that caused traffic accidents when they first appeared on Washington streets. As one astonished onlooker remarked to her husband, "Some of them seem to be nice girls!"

Chapter 3: Breaking Japanese Codes: Turning the Pacific War (1942-1943)

The first six months after Pearl Harbor represented the darkest period of the Pacific War for America. Japanese forces swept through Southeast Asia with stunning speed, capturing Guam, Wake Island, Hong Kong, Singapore, the Philippines, and much of the Dutch East Indies. By May 1942, Japan controlled a vast empire stretching from the Indian Ocean to the mid-Pacific. As Winston Churchill grimly observed, "Over all this vast expanse of waters Japan was supreme, and we everywhere were weak and naked." Into this desperate situation stepped the newly recruited female code breakers. In June 1942, seventy-four women from elite colleges arrived at the Navy's downtown Washington headquarters and were immediately thrust into critical work on Japanese naval codes, particularly JN-25, the main fleet cipher. Breaking this system required extraordinary patience and attention to detail. The Japanese used a massive codebook containing about thirty thousand five-digit groups, each representing a word, syllable, or phrase. Before transmission, each code group was disguised using an "additive"—another five-digit number added to it using a peculiar kind of math with no carrying of digits. The tide began to turn in June 1942 with the Battle of Midway, where code breaking played a decisive role. Admiral Nimitz knew the Japanese plans thanks to cryptanalysts reading JN-25, allowing American forces to ambush the Japanese fleet. The resulting American victory marked the first major turning point in the Pacific War. As the conflict progressed, women like Anne Barus from Smith College spent years recovering Japanese additives, working with yard-long sheets filled with rows of five-digit numbers. When they found a valid additive, it was recorded in a book they were rebuilding through painstaking analysis. Beyond JN-25, women worked on what were called "minor ciphers"—auxiliary systems used for communication between captured islands, weather lookouts, and supply ships. These systems often proved vital when the main fleet code temporarily went dark after security changes. Elizabeth Bigelow, a Vassar graduate, once deciphered a badly garbled message within hours, revealing a Japanese convoy sailing that day. When told her work had helped sink the convoy, she felt "terribly pleased." Other women decoded messages from Japanese soldiers retreating into the jungle during the Battle of Guadalcanal, giving them a plaintive glimpse of men facing certain death: "I have not seen the sea for two weeks. I have not seen the sky for three weeks. It is time for me to die for the Emperor." By late 1943, women outnumbered men more than two-to-one in the JN-25 section. Their work helped American submarines locate and sink Japanese merchant ships, severing the supply lines to Japan's far-flung island garrisons. This intelligence advantage transformed the Pacific War, allowing American forces to target Japanese weaknesses with unprecedented precision. As one female code breaker later reflected, "Never in my life since have I felt as challenged as during that period. Like Hegel's idea about when the needs of society and the needs of an individual come together, we were fulfilled."

Chapter 4: Atlantic Triumph: Defeating the U-boat Enigma (1943-1944)

While the Pacific War raged, an equally desperate struggle unfolded in the Atlantic. Winston Churchill described the Battle of the Atlantic as the thing that worried him most, believing that whoever won this battle would win the European war. In early 1942, German Admiral Karl Dönitz launched what U-boat crews called the "Happy Time," sending submarines to cruise America's East Coast. Ships were sunk within sight of American beaches, with the Outer Banks of North Carolina becoming known as "torpedo junction." The situation worsened in February 1942 when the German Navy added a fourth rotor to its Enigma machines, creating a cipher the Allies called "Shark." This innovation rendered previous British code-breaking methods ineffective. For ten months, Allied ships were sunk at an alarming rate, with no way to locate the U-boats. It was during this critical period that women like Margaret Gilman, a biochemistry major from Bryn Mawr who had studied German in high school, found themselves in sealed rooms attacking Shark. Her unit consisted almost entirely of women, with a lone male officer supervising. The urgency was harrowing. "German submarines were literally controlling the Atlantic Ocean," Margaret recalled later. "Can you imagine sending out American troop ships loaded with soldiers through an Atlantic ocean riddled with submarines? It was heart-rending." In her workroom, a detailed wall map displayed the Atlantic Ocean with pins for every U-boat whose position they could locate. Margaret couldn't stand to look at the map and would position her head to keep it out of her peripheral vision. The breakthrough against Shark came through an extraordinary engineering project centered in Dayton, Ohio. The U.S. Navy established a secret facility at the National Cash Register Company, where inventor Joseph Desch designed high-speed decryption machines called "bombes." Six hundred WAVES were sent to Dayton to wire the complex commutator wheels that would power these machines. Working in shifts around the clock, these women meticulously soldered wires according to precise diagrams, never knowing exactly what they were building. By September 1943, the bombes were breaking Shark consistently, often within hours of intercepting messages. This intelligence revolution transformed the Battle of the Atlantic. Allied convoys could be routed around U-boat wolfpacks, while hunter-killer groups targeted submarines with devastating precision. The tide turned dramatically—for every Allied merchant vessel sunk, seven U-boats were now being destroyed. By May 1944, half the operational U-boat fleet had been sunk, with over three-quarters of their crews killed. The human cost of this work was significant. The women operated under intense pressure, knowing that delays in breaking a key might mean hundreds of sailors' deaths. Louise Pearsall, a mathematician who helped design the bombe menus, worked seven days a week, twelve hours a day. Others suffered from exhaustion and anxiety. Yet they persevered, driven by patriotism and the knowledge that their work was saving lives.

Chapter 5: D-Day and Beyond: Intelligence for Victory (1944-1945)

The planning for D-Day—the Allied invasion of Normandy—represented the pinnacle of wartime intelligence cooperation. Female code breakers made two crucial contributions: they provided detailed information about German coastal defenses, and they created elaborate deception operations to mislead the enemy about Allied intentions. At Arlington Hall, women breaking the Japanese diplomatic Purple cipher intercepted messages from Baron Oshima, Japan's ambassador to Germany. After touring the Atlantic Wall fortifications, Oshima sent Tokyo detailed reports on German defensive preparations, unwittingly providing Allied planners with invaluable intelligence about Normandy's relatively weaker defenses. Simultaneously, women at Arlington Hall created sophisticated fake radio traffic to support Operation Fortitude, the deception plan designed to convince Germans that the main Allied attack would target Calais rather than Normandy. These women analyzed genuine American military communications patterns, then replicated them to create convincing traffic for a fictitious army supposedly gathering in southeast England under General Patton. This phantom force, called the First U.S. Army Group (FUSAG), existed only in carefully crafted communications that German intelligence eagerly intercepted and believed. When D-Day finally arrived on June 6, 1944, the women at the Naval Communications Annex were among the first Americans to learn of it. Ann White, working the midnight shift in the German section, received an intercepted Enigma message reading simply: "Enemy landing at the mouth of the Seine." Throughout that historic day, the code breakers followed the invasion through German eyes, reading frantic messages about Allied paratroopers, naval bombardment, and amphibious landings. Their work helped Allied commanders respond quickly to German defensive movements, contributing significantly to the operation's success. The human dimension of this momentous day was profound for the women code breakers. Jimmie Lee Hutchison Powers, a WAVE who operated bombe machines, learned that her husband Bob had been killed piloting a glider into Normandy during the first wave. Despite her devastating loss, she was denied leave to attend his funeral—the work was too important to spare even one operator. Many other women received similar news about brothers, fiancés, and friends. They continued their work through grief, knowing their efforts were saving countless other lives. As the war entered its final phase in 1945, the women faced both triumph and tragedy. Elizabeth Bigelow lost her beloved brother Jack when his aircraft carrier was struck by a kamikaze attack during the Battle of Leyte Gulf. Virginia Dare Aderholdt, an expert on the Japanese diplomatic code, personally decoded the surrender message as it arrived on August 14, 1945. Working with remarkable speed, she translated the message in real-time, allowing President Truman to announce Japan's capitulation to the American public. When the news was shared at Arlington Hall, the women who had kept this momentous secret were finally released from their oath of silence and joined the jubilant celebrations in Washington's streets.

Chapter 6: Hidden Legacy: Secrecy and Post-War Impact (1945-Present)

When World War II ended in August 1945, the more than 10,000 women who had served as code breakers faced an uncertain future. Many received what they called the "Here's your hat, what's your hurry" speech—a thank-you for their service followed by encouragement to leave government employment and return to traditional female roles. Brigadier General Preston Corderman gathered Arlington Hall employees and told them it was their patriotic duty to get off the government payroll. Most women complied, returning to civilian life without ever revealing the crucial work they had performed. The transition was often difficult. Despite their extraordinary wartime achievements, many women found limited professional opportunities in the post-war era. Elizabeth Bigelow, who aspired to become an architect, applied to several prestigious architecture programs using her GI Bill benefits. Each school responded that they were "saving all spaces for men who had been in the armed services." When she pointed out that she had served in the WAVES for two years, they still refused her admission. Similarly, Louise Pearsall, who had helped design tests for the bombe machines, suffered a nervous breakdown after the war and struggled to find meaningful employment that utilized her mathematical talents. Some women, however, did continue in intelligence work and helped establish America's post-war cryptologic institutions. Ann Caracristi returned to Arlington Hall after a brief departure and eventually rose to become the first female Deputy Director of the National Security Agency (NSA). Wilma Berryman, who had led the Japanese Army address section during the war, became a pioneer in Chinese cryptanalysis during the Cold War. Juanita Morris, who had worked on German diplomatic codes, later played a crucial role during the Cuban Missile Crisis. These women helped build the foundation of modern American signals intelligence. The secrecy surrounding their wartime contributions remained so absolute that most took their stories to their graves. Many never told even their husbands or children about their real wartime roles. Dot Braden Bruce, who married her wartime correspondent Jim Bruce in December 1945, kept her oath of secrecy for over 50 years. When she finally began hinting at her code-breaking past, her family initially didn't believe her. The women's collective story remained largely untold until the 1990s, when declassification of wartime records finally allowed their contributions to be acknowledged. The legacy of these female code breakers extends far beyond the specific battles they helped win. They demonstrated women's intellectual capabilities at a time when such opportunities were severely limited. They pioneered roles in mathematics, cryptanalysis, and computer science that would eventually open to later generations of women. Perhaps most importantly, they proved that in matters of national security and intelligence, talent and dedication transcend gender. Their groundbreaking work helped establish the centrality of signals intelligence to modern warfare and laid the foundation for America's continued leadership in this critical field.

Summary

The story of America's female code breakers represents one of history's most remarkable intersections of necessity, opportunity, and talent. Facing existential threats in both the Pacific and Atlantic theaters, the United States military reluctantly opened its doors to women with analytical minds, creating a meritocracy of intellect where gender temporarily became secondary to ability. These women—from elite college graduates to small-town schoolteachers—seized this unprecedented opportunity and proved themselves indispensable to the Allied victory. Their achievements transformed modern warfare by demonstrating the decisive power of signals intelligence. By breaking Japanese diplomatic, army, and naval codes, they enabled victories at Midway and Leyte Gulf, guided submarine attacks that strangled Japan's supply lines, and provided the intelligence that led to Admiral Yamamoto's death. By cracking German Enigma ciphers, they helped defeat the U-boat threat in the Atlantic and supported the D-Day invasion that liberated Western Europe. Yet perhaps their most enduring legacy lies in how they silently challenged prevailing assumptions about women's capabilities. In the pressure-filled environment of wartime intelligence, they proved that analytical thinking, mathematical reasoning, and leadership were not male preserves. Though most returned to traditional roles after the war, they had demonstrated that when barriers fall, talent rises—a lesson that would eventually help transform American society in the decades that followed.

About Author

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Liza Mundy

Liza Mundy is an award-winning journalist and the New York Times bestselling author of five books, including CODE GIRLS, and her latest, THE SISTERHOOD.Published in 2017, CODE GIRLS tells the story of more than 10,000 female code breakers recruited during World War II to perform work that saved countless lives, shortened a global war, and pioneered the modern computer and cybersecurity industries.Available October 2023, THE SISTERHOOD is a gripping history of women in the CIA across three generations--beginning with unlikely female spies who served in the war and its aftermath, through to the women who tracked down Osama Bin Laden.Her other titles include MICHELLE: A BIOGRAPHY; THE RICHER SEX; and EVERYTHING CONCEIVABLE. In addition to her work as a narrative non-fiction author, Liza, a former staff writer for The Washington Post, writes about history, culture, and politics for publications such as The Atlantic and Politico.At various points in her life as a working parent she has worked full-time, part-time, all-night, at home, in the office, remotely, in person, on trains, in the car, alone, in crowds, under duress, and while simultaneously making dinner.

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