mowque
Banned
You're going to need a string of lucky breaks for Germany to repel the invasion, some of which nigh-have to be weather related. Even then, the allies get a (bad) bloody nose, and try again later, after turning more of German occupied Europe into a convincing stand-in for the moon.
Yeah. Really, unless you can convince Neptune to help out, it is tough. The Allies had way more planning, resources and men committed. They got to pick the time and place. They had total air supremacy, and KNEW HOW TO USE IT. They attacked with experienced, well armed troops (and the Allies even had time/resources to dedicate to making special gear and weapons just for this one attack).
The Mulberry harbors are a perfect example of how much was dedicated to this one operation. The Allies came loaded for bear. It would be tough to throw them back, unless we really start messing with Nazi priorities.