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.
N is for Normandy
One of the most important factors in the success of the Allied invasion of Normandy was that the Germans believed that the invasion would happen at Calais, two hundred miles to the north. It was a natural conclusion – the narrowest part of the English Channel is between Dover, England and Calais, France.
Here’s how American codebreakers contributed to that misperception.
One under-sung role of codebreakers is to monitor the transmissions and communications of your own side. Americans wanted to make sure that their radio operators weren’t making the same mistakes that German and Japanese radio operators made. Those mistakes gave inroads for people working in Arlington Hall and Bletchley Park to break enemy codes. To prevent Axis codebreakers from making similar strides, Americans monitored their own traffic. This work was done mostly by women, members of the Women’s Army Corp, stationed at Arlington Hall.
When it was time to create a phantom army in eastern England, the First U.S. Army Group or FUSAG, the women who were monitoring real communications were exactly who was needed to create the fake ones.
“In order to create fake traffic, the women had to understand every last thing about the real traffic that went out, and the circuits and stations it traveled through. Once created, fake traffic had to be routed. The women had to create a plausible schedule; release prearranged dummy traffic to be transmitted during times when such traffic might be expected; maintain circuit flow; and monitor what went out. They had to understand the circuits, the call signs, the frequency, the peak volume times: everything.” (pp. 304-5, Code Girls by Liza Mundy).
This fake army assembled well before D-Day and continued well after the initial invasion. The Allies wanted the Germans convinced that an invasion of Calais was still imminent so that they didn’t send their forces south to fight the actual invasion in Normandy.