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.

M is for Magic

When I’m wading in the weeds of the how-to of decoding and decrypting secret messages, I sometimes forget the purpose of all of this. The point of learning what the enemy said is to provide intelligence to the people who are tasked with developing strategy.

The generals can’t read every intercepted message or spend time figuring out what they mean in context with previous messages. That’s the job of intelligence officers.

This was nicely illustrated in yesterday’s story. A bunch of people in Hawaii intercepted, decoded, and translated messages. An intelligence officer, Edwin Layton, was made aware of the most relevant items. In turn, he summarized the gist of what was learned and aided the general in figuring out how to use that information.

There’s always a tension between sharing too much with higher-ups (to the point of overwhelm) or too little (to the point of not getting the right information to the right person at the right moment).

Magic was the name for the intelligence derived from the Japanese code system that the Americans called Purple. Purple was used by Japanese diplomats around the world. William Friedman led the team that initially broke Purple, late in the summer of 1940.

“Previously, signals intelligence had circulated within the War Department and to outside parties, such as the State Department, in the form of verbatim translations of decrypted messages. These translations went to the customers without any commentary or analysis.” (p. 107, Secret Messages by David Alvarez)

Magic changed all of that.

“The Magic Diplomatic Summary was an instrument for making the signals intelligence product more user-friendly. Each day Special Branch received (via teleprinter or courier) several sets of all messages translated by SIS in the previous twenty-four hours.” (p. 107)

Those messages were distributed to editors in charge of particular geographies or topics. Just like with a newspaper, the editors summarized the information from the messages, incorporating information from other sources.

“By the last year of the war, the daily summary was routinely twelve to twenty pages long and reported a range of diplomatic, military, and economic topics.” (p. 108)

To learn more, I recommend Secret Messages: Codebreaking and American Diplomacy, 1930-1945 by David Alvarez and The American Magic: Codes, Ciphers, and the Defeat of Japan by Ronald Lewin (published as The Other Ultra in Britain).