[Cryptography] Review of "Code Girls" by Liza Mundy

Arnold Reinhold agr at me.com
Tue Apr 30 23:57:03 EDT 2019

The Final Countdown was a 1980 alternate-history film about a modern nuclear aircraft carrier that travels through time to the day before the 1941 Japanese attack on Pearl Harbor. Filmed on board the USS Nimitz, The Final Countdown was a moderate success at the box office. (Wikipedia)

So here is a concept for another World War II fantasy film: the U.S. War Department, short on manpower, staffs an entire battleship with women. The clever females on this Top Secret mission track down and sink the majority of Japan’s transport ships. Their success enables General Douglas McArthur to conquer island after island defended by poorly equipped and weak-from-hunger Japanese troops. For an added kicker, the women recover Japanese plans for defending their home islands, influencing President Truman to use the atomic bomb to end the war without the planned bloody invasion of Kyūshū. After the war, most of the women, sworn to secrecy on pain of execution, return to traditional roles and take their stories to the grave. 

This plot may seem even more far-fetched than The Final Countdown, except that it is very close to what really happened. The women weren’t on a battleship, they were in a commandeered girl’s school in Arlington, Virginia, just across the Potomac from Washington D.C. And they weren’t firing 16-inch guns at the transport ships, they were breaking Japanese Army codes and unscrambling position reports transmitted regularly by the ships. Those decoded reports kept the U.S. submarine fleet busy sinking two-thirds of the Japanese merchant marine by the end of the war. But for those women, the fanatic and well dug in Japanese soldiers might have held on much longer, or even thrown back some of McArthur’s assaults.

All this is recounted in Liza Mundy’s Code Girls, (Hachette Books, 2017, ISBN|978-0-316-35253-6) an account of the thousands of women recruited for U.S. cryptologic work before and during World War II, including top analysts such as Elizebeth Friedman and Agnes Driscoll, lesser known but outstanding contributors like Genevieve Grotjan Feinstein and Ann Zeilinger Caracristi, and many others. 

Mundy has a chapter titled “Pencil-Pushing Mamas Sink the Shipping of Japan.” It’s a tad misleading. Most of the women were single and any discovered pregnancy would get you fired. But other than that, the title is accurate. By 1944, the job of breaking Japanese Army codes, especially the 2468 code used for transport ships, was woman staffed and woman led. The results were devastating. Black humor in the Japanese military was that one could walk from Singapore to Tokyo on the periscopes of U.S. submarines. In fact there were not enough subs to exploit all the position reports the women decrypted. The women’s efforts left Japanese Army troops without reinforcements, supplies, medicine and food. More Japanese soldiers died of starvation and illness that were killed by bullets and bombs.

There is a scene in another movie, 2014’s The Imitation Game, where Joanne Clarke shows up late at a qualifying examination for cryptanalysts and is told the openings are not for women and that the secretarial exams are on a different floor, but Alan Turing tells her to sit down and she bests the men. The reality, at least in the U.S., was that smart women were very much wanted from the beginning.

In 1939 young Genevieve Grotjan (I am posting this on her 106th birthday) took a math test for an unrelated civil service job and did very well. William Freedman, our top cryptanalyst, apparently had feelers out for such things, and hired her. Perhaps the most dramatic moment in the book takes place at 2 pm, September 20, 1940 with Grotjan patiently trying to get the the attention of Frank Rowlett, who was engrossed in conversation with male colleagues. She has found evidence of cyclicality in the Japanese cipher the U.S. codenamed Purple. Cheers erupt, toasts of Coca Cola are poured and Friedman, under severe pressure to break Purple, slumps against a table. A decryption machine for Japan’s main diplomatic cipher is constructed a couple of weeks later. It wasn’t a solo effort on Grotjan’s part of course, other women and men had helped assemble several long enciphered texts with the same indicator and laboriously transformed them to matching plugboard settings. 

By November 1941, a month before Pearl Harbor, the U.S. Navy was asking top women’s colleges for names of their best seniors who were then sent letters inviting them to secret meetings. There they were asked if they were planning marriage (a disqualification) and if they liked crossword puzzles. The women who passed were invited to take correspondence courses in cryptography. Those that did well were offered jobs in Washington.  The Army soon followed, but had to find their own schools, a no poaching agreement prevailed, and soon focused on teachers colleges. Once the Army and Navy began accepting women, the smartest woman enlistees were assigned to code breaking.

Code Girls is not just another story of women playing their part in the war; we all knew about Rosie the Riveter. This is different. The decision to recruit large numbers of smart women to the code breaking effort was a strategic move that could rank with Einstein’s letter to Roosevelt and the Tizard mission that brought the cavity magnetron to the U.S. as decisive in WW II.

Mundy points (p. 80) out that Germany and Japan were more traditional societies and discouraged women from war work. The Nazis emphasized the traditional German Kinder, Küche, Kirche dogma that women should concern themselves with domestic duties and even created a Cross of Honor of the German Mother medal for pure German women with four or more children. Their failure to utilize their female intellectual talent put them at a major disadvantage, thank goodness.

This book is written for a broader audience than cryptography geeks. There is plenty of material about the women’s personal lives: finding living accommodations in overcrowded war-time Washington, corresponding with soldiers overseas (a major pastime apparently), dating and finding husbands. One of my favorite bits is Mundy’s detailed description of the spiffy new Navy WAVE uniforms, filled with fashion jargon as impenetrable to me as cryptographic terminology must be to lay people.

But there is plenty of interest for the geek crowd, Mundy does an excellent job explaining concepts like depth, modular addition and checksums, and paints a convincing picture of the day-to-day operation of the code breaking effort. Even after a code is cracked there is still a lot of work to do, much of it rote, but much creative too, as Japan kept changing and improving its encryption.

College graduates in 1942 would be in their late 90s today and only a few were still alive for Ms. Mundy’s research. It sad that it took so long for these woman’s stories to be told, the women’s strict obedience to the war time secrecy oaths was a factor, but it's wonderful that it has finally been written.

Happy birthday Genevieve!

Arnold Reinhold
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