Eisenhower et. al. were sweating bullets over the weather forecast, and if they had known that the Germans had an additional division of forces in Normandy they would have probably delayed - and possibly ultimately abandoned - D-Day. And if the Germans had had Hillary-scale leakage of classified information coming to them - rather than quite the reverse - they wouldve had enough additional divisions in Normandy to make an attempted opposed landing there utterly unthinkable. Quite simply, too hard."
We had another alternative that was successful. It would have split Hitler’s forces in France.
https://en.wikipedia.org/wiki/Operation_Dragoon