But for the attack to succeed, the Allies needed to ensure that the Germans were taken by surprise. The success of a cross-channel invasion depended on making sure that Allied soldiers did not encounter a full complement of German coastal defenders when they landed. The Allies also needed to be sure the Germans did not figure out what was happening in time to pull mobile reserve troops out of other areas and send them to help defend Normandy. One way to achieve surprise was by creating what Winston Churchill called a “bodyguard of lies” to protect the kernel of truth about the exact time and place of the landings.
And so, in the months running up to the invasion, the Allies created a brilliant deception program—the aptly named Operation Bodyguard—designed to sow confusion about when and where an Allied attack would happen. The goal was to persuade the Germans that Allied forces were bigger and more spread out than they actually were and that an invasion of Europe would occur in several places near simultaneously. They wanted the Germans to believe that the central attack, when it came, would come in the Pas de Calais, the region around Calais. To do this, the Allies created a “phantom army,” a fictitious force to throw the Germans off the scent. They engaged double agents—spies for Germany in England who were turned by the British and made false radio reports back to Germany, spreading the word that the fake army was real and was massing for an attack. But for a fake army to seem truly convincing, it needed something else, something invisible and yet powerful: fake communications.
When Allied commanders were planning the multitude of logistics around D-Day, they had to think about many things, and communications was one of them. How would incoming GIs lay down phone lines and erect radio stations as they landed on the beaches and proceeded to race across France and into Belgium? This is the central mission of the Army Signal Corps.
The Allied commanders also had to assume that—even before the landing took place, as troops were assembling in England—Germans were busily doing to the Allies what the Allies were busy doing to them: monitoring radio traffic to construct the Allied order of battle and figure out who was moving where. The Germans controlled so much of the coast that they could monitor even low-frequency Allied traffic. There was no way the American, British, and Canadian units could communicate and be sure that the Germans did not pick up their transmissions. Even if the Germans didn’t break their coded conversations, the enemy could learn a lot from traffic analysis. “So great were the chances of all the traffic that we transmitted above a certain power being received somewhere in occupied territory, that it had to be assumed that all of it was read,” said a postwar Signal Corps memo. The Allies’ solution? Fill the airwaves with fake traffic.
Actually, the Allies created two phantom armies. One existed to persuade the Nazis that an Allied force was massing in Scotland to mount an invasion of Norway. The goal of that deception, known as Operation Fortitude North, was to persuade the Germans to keep the troops that were stationed in Norway where they were, and not to divert them to France once the landing began.
The other phantom army was known as the First U.S. Army Group, or FUSAG, and it was supposedly led by George Patton, the American general whom Rommel most respected and feared. This was known as Operation Fortitude South. Patton’s fictitious FUSAG was supposed to be massing in Kent and Sussex, to make a cross-channel attack on the Pas de Calais. Patton was, in fact, in England; the First Army, however, was not, nor was it anywhere.
It was crucial that the Germans not only believe in Patton’s fictional First Army Group, but also continue to believe in it even after the D-Day landing. They must continue to think that the Normandy invasion was a diversionary attack to distract attention from the big one coming in the Pas de Calais. Believing that, the Germans would keep the bulk of their defensive forces in the Pas de Calais, giving the Allies time to establish a Normandy beachhead and begin the liberation march to Paris.
For a fictitious army to be believed, it had to send the exact sort of radio traffic that a real army would send. The radio traffic had to come into existence well before the attack was launched, and it had to stay in place for weeks after, even as the same transmitting stations were being used for real military communications. Creating and directing this traffic was a complex and highly important job; there could be no mistakes, nothing strange or untoward to attract notice. Much of it would be done at Arlington Hall by the women who had fallen for that inviting pamphlet and joined the WACs.
The ploughman homeward plods his weary way. The ploughman plods homeward his weary way. The ploughman plods his weary way homeward. The ploughman his weary way homeward plods. The ploughman his weary way plods homeward. His weary way the ploughman homeward plods. His weary way homeward the ploughman plods. His weary way the ploughman plods homeward. Homeward the ploughman plods his weary way. Homeward his weary way the ploughman plods.
Everywhere in the cryptographic unit of Arlington Hall, posters on the walls reminded staffers sending out coded messages to vary the order of the texts. “There’s always another way to say it,” exhorted one poster, demonstrating how lines from Thomas Gray’s “Elegy Written in a Country Churchyard” could be rearranged. At Arlington, the staff of eight thousand did more than break enemy messages. They encoded American traffic and monitored that traffic to make sure it was secure. They were obsessively reminded to avoid the sorts of stereotypes and predictable repetitions that had given Americans an entering wedge into Japanese and German codes. “Parallel texts lost a battle,” the posters pointed out, reminding the encoders that in World War I, a battle had been lost because a single message was sent both in cipher and in the clear. “Shifting position of words and substituting synonyms and using passive voice of verb” are all ways to vary the order of a sentence, the posters reminded them.