Images may be AI generated and not historically correct.
The Team
Whenever The Battle of Midway is talked about, the word "codebreakers" always has to be a part of the conversation. Had it not been for these guys, the battle would most likely have never turned out the way it did. As it was, the outcome of this huge and historically significant clash between The U.S. Navy and the world's largest and most modern navy of that era was due in part to a large amount of good luck on our behalf. And... a lot of that luck came via the codebreakers themselves.
The "codebreakers" were officially known as the U.S. Navy's "Combat Intelligence Unit". Also known as Station HYPO. The unit was based at Pearl Harbor, Hawaii and was led by Lieutenant Commander Joseph Rochefort. I couldn't find the actual number of team members, but it was comprised of several codebreakers, linguist and radio traffic analysts.
Another key figure in determining what the Japanese were planning was Lieutenant Commander Edwin T. Layton, the Pacific Fleet Staff Intelligence Officer. He was the liaison between the intelligence team and Fleet Command. He and Rochefort had spent three years together in Japan earlier studying the Japanese language and culture.
Lieutenant Commander Joseph John Rochefort joined the navy in 1918, lying about his age at the time. He was a major figure in creating the navy's cryptographic and intelligence operations from 1925 to 1946. According to records, he was an expert Japanese linguist and trained cryptanalyst. He was the Officer in Charge of HYPO and had hand-picked a lot of his team himself. By the time of Pearl Harbor, he had the best cryptanalyst, linguist and traffic analyst in the navy. And these men were the unsung heroes behind the greatest victory in the history of the United States Navy as they had figured out how to break a lot of the Japanese main code JN-25b.
The "Ruse"
Rochefort and his team had become quite adept at picking clues out of the code in intercepted messages between the Japanese fleet and its headquarters. They could intercept, decrypt, and translate a lot of it within hours of when it was sent. In May of 1942 they received several messages that seemed to suggest that Admiral Isoroku Yamamoto was preparing for a major invasion of a location designated "AF". But... no one could figure out what AF stood for. Rochefort and Leyton believed that the location was the atoll of Midway where the US Navy had a small, but very important naval air base. They felt that the Japanese plan was to take Midway which would allow them a launching platform to attack and invade The Hawaiian Islands which in turn would provide a perfect launching point for attacks on the West coast of The U.S. To determine whether their suspicion was correct or not, they developed a little ruse.
On May 20th, 1942, Fleet Intelligence at Pearl had the base on Midway send out a false, unencrypted message in the open that its freshwater plant was down. The Japanese should have figured out that this was unusual for the US to send an unencrypted message in the open like that, but no one in their command did or said a thing about it. In fact, within hours, the Japanese sent a message back to their headquarters that "AF" had a problem with their water plant and was short of water. This message was picked up by Fleet Intelligence and translated by Rochefort's team.
The Win
The cat was out of the bag! This indeed proved to Fleet Command that "AF" was, without a doubt, Midway atoll. That's when Admiral Chester Nimitz immediately realized that this was a prime opportunity to put together a little welcome party for the Japanese task force when they arrived!
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