The A to Z Challenge asks bloggers to post 26 posts, one for each letter of the English alphabet, in April. Most of us choose to make these posts on a particular theme. My theme for 2022 is Codebreaking in World War II, which fits with the topic of the novel that I’m writing. Visit every day (except Sunday) in April for a new post on my topic.

D is for Agnes Meyer Driscoll

Agnes Meyer Driscoll (1889-1971) was a leading American cryptanalyst for the US Navy in both world wars and beyond.

During World War I, she enlisted in the Navy and worked in the Code and Signal section. At that time, her work was focused on encoding America’s messages to keep them secret from the enemy.

Agnes Meyer Driscoll

After the war, she kept working for the Navy as a civilian. Between the wars, she worked on testing and developing machines to make and break ciphers. She was well known (within the secretive community that did this sort of work) to be good at breaking the hearts and future fortunes of inventors. An inventor would bring in a machine, claiming that it produced unbreakable ciphers, only to watch Driscoll decipher it.

For much of the 1930s, Agnes Driscoll worked in Room 1645 of Navy headquarters on the Japanese naval fleet code. The Japanese used a codebook to make their message, and then complicated it further with a transposition cipher (see yesterday’s post for that definition). Each time that the Japanese changed the codebook, a standard security measure, Driscoll started anew.

“Her feat had enormous real-world impact. In 1936, Driscoll’s efforts revealed that the Japanese had refitted a battleship that now could travel in excess of twenty-six knots. The United States didn’t have a ship that fast, so the Navy upgraded a new class of battleships to exceed that speed.” (p. 81, Code Girls by Liza Mundy)

With all of that success in the 1930s, history buffs might wonder why we didn’t know that the Japanese Navy was going to attack Pearl Harbor. The Japanese revamped the entire system in 1939. Driscoll and colleagues made progress on the new system, but even that was thwarted when the system was partially changed again in early December 1941.

Driscoll trained nearly everyone in the Navy who led code-breaking efforts for the Navy in World War II. One of her trainees was Edwin Layton, who we’ll meet again when we get to the letter ‘L.’ Here’s what he had to say about Agnes Meyer Driscoll:

“She not only trained most of the leading naval cryptanalysts of World War II, but they were all agreed that none exceed her gifted accomplishments.” (p. 78, Code Girls by Liza Mundy)

If you want to learn more about Agnes Driscoll, check out her page on the NSA website or read about her work with more detail and more context in Code Girls by Liza Mundy.