Code Name Purple: A True Story of Courage, Love, and Madness in World War II

by Amy Butler Greenfield

The thrilling true story of the unlikely American codebreakers who cracked Japan’s top cipher machine, eavesdropped on Hitler, and helped win World War II.

In 1937, Japanese engineers invented Purple, a cipher machine capable of scrambling a message more than 500 quadrillion ways. It encrypted many of the Axis powers’ deepest secrets, including crucial conversations with Hitler and his inner circle. Because the machine was so advanced, Japanese leaders believed it was perfectly secure.

In 1940, a scrappy team of American codebreakers in Washington DC proved them wrong.

Sweeping from the Great Depression through to the final victories of World War II, Code Name Purple tells the riveting story of the outsiders who broke Purple. Mostly civilians, they came from a myriad of backgrounds, faiths, and life experiences. Many were women, Jewish, or disabled. Working in shabby rooms on a shoestring budget, they accomplished one of the greatest codebreaking feats of all time. Their work helped defeat the Axis powers, including the Nazi regime that considered so many of them subhuman.

Drawing on thousands of pages of interviews, personal papers, and recently declassified documents, award-winning historian Amy Butler Greenfield brings these outsized characters to life. Among them are William Friedman, an enigmatic genius who risked his sanity to solve Purple; John Hurt, an ailing language whiz who worked from a bed in a secret vault; Genevieve Grotjan, a shy mathematician who made a brilliant breakthrough; and Leo Rosen, a young engineer who braved the journey to Britain’s Bletchley Park, where a secret Purple-Enigma exchange supercharged Allied codebreaking.

This enthralling narrative history captures not only the team’s work, but their lives—their parties, arguments, anguish, friendships, romances, and courage in peace and war. Set in an era when no one knew if people could keep up with machines, Code Name Purple is a powerful story of challenge, resilience, and what it means to be human.

Genres: Nonfiction, History

464 pages, Hardcover

Expected publication May 11, 2027

About the author

Amy Butler Greenfield writes award-winning books about history, science, art, and spies. Her work has been published in ten languages.

Her history of the red dye cochineal, A Perfect Red, won the PEN/Albrand Award for First Nonfiction and France’s Prix du Livre Environnement. Her acclaimed biography of Elizabeth Smith Friedman, The Woman All Spies Fear, was optioned for film. Her first mystery for children, Ra the Mighty, was an Edgar Award finalist. Her next book, Code Name Purple, is about an underdog team of codebreakers who cracked a top WWII cipher machine and eavesdropped on Hitler.

An enthusiastic and experienced presenter, Amy has appeared on the History Channel, PBS’s American Experience, and other television and radio programs. She has given popular talks across the country, and she has been a featured speaker at the International Spy Museum, London’s National Gallery, the Oxford Symposium, the Los Angeles Public Library, the National Cryptologic Foundation, and UK intelligence agency GCHQ.

Born in Philadelphia, Amy grew up in the Adirondack Mountains and studied history at Oxford as a Marshall Scholar. She now lives with her family in England, not far from Bletchley Park, where part of the Purple story took place.