Answer:
The Allies staged a fake attack at Calais.
Explanation:
Eisenhower set up a fake army to fool the Germans into thinking that Calais would be invaded, the Allies then took the opportunity to attack Normandy (as they moved troops to "defend" against a potential attack there.
This fake army was set up in Dover, U.K and was visible from German Intelligence, it had fake tanks and planes to make the illusion real.