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.

L is for Edwin Layton

Edwin Layton was one of many US Navy codebreakers trained by Agnes Driscoll. I quoted him in the D is for Driscoll post,

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)

Layton was involved in one of the most famous successes of codebreaking in World War II, the Battle of Midway in early June 1942.

One reason that this incident is famous is that it’s relatively easy to understand without a deep knowledge of how codebreaking works. The other reason, of course, is because the Battle of Midway was such a decisive and damaging defeat to the Japanese Navy, six months after the devastating attack on Pearl Harbor.

Layton, an intelligence officer, served as a liaison between Admiral Nimitz and the naval cryptography unit in Hawaii. That unit had partially broken the Japanese Navy’s code that the US labeled as JN-25b code. In the spring of 1942, they knew that the Japanese were planning an attack on a target labeled “AF.”

The problem was that the cryptanalysts in Hawaii were convinced that AF was Midway, while the naval experts in Washington DC and other officers on Nimitz’s staff were convinced that the next attack would happen elsewhere. Layton argued strongly enough that he was ordered by Nimitz to tell the cryptographic unit that “positive identification of AF should receive the highest priority” (The Other Ultra by Ronald Lewin, p. 108)

Sources disagree on who had the initial idea, but here’s what was done: Midway was ordered to send out an uncoded radio signal claiming that their water purification plant had broken down. Less than 24 hours later, the Japanese sent the notice that “AF was short on water.” That confirmed that Midway was the target and meant that Nimitz could position aircraft carriers in the perfect spot for a counterattack.

For more information, check out the The Other Ultra by Ronald Lewin or the 2019 film, Midway.