What if German Intelligence managed to find out that the allied forces were planning to invade Normandy? Well for a start, a wave of soldiers would relocate to the beaches of Normandy waiting for the Allies to come at June 6.
Before D Day
Somehow, let's presume that German Intelligence found out that Operation Overlord was due to start on 6 June, Hitler orders a mass migration of German Soldiers and the new ME 262 jet fighter to defend Normandy.
The Battle Begins
As the allied landing craft approach Omaha Beach, a wave of ME 262s descend from the skies destroying every allied fighter in view, without cover the invasion is a quick failure and allied generals suffer humiliation.
Stalin saw this as a outrage seeing that this invention would soon be deployed to the Eastern front, the atomic bomb was also on its way, and on June 1945, a desperate Reich drops a atomic warhead on Stalingrad and New York, ending the war.