As a part of the preparations for the invasion of France, the Allies used deception to try to fool the Germans into mistaking locations of invasions.
One such effort was called Operation Fortitude- South, trying to convince the Germans that the invasion of France would occur at Pas-de-Calais. To do this, HQ created a fake unit, called First United States Army Group, and named the at the time disgraced General Patton (following the Sicily hospital slapping incident) to lead it. Secret agents fed the Germans false information, and dummy buildups of forces and radio traffic were made all over southeast England.
Fake tank used to deceive aerial recon:
Activity was increased around the Dover area and heavy bombing raids were conducted around the Pas-de-Calais area, leading the Germans to keep 15 divisions on alert in that area. These divisions were held in that area even after the landings in Normandy, for fear that they were only a diversion from the real invasion coming across from Dover.
Deception plans map: