When they launched the attack, Eisenhower had his resignation speech, taking the blame for everything if it failed, all prepared and pinned inside his jacket. It was a huge risk, and everything depended on the determination of the troops heading in. The British, Canadian, and American troops there deserve more accolades than we can give them.
And also, given the word the day before, the French Resistance blew the train tracks all through southern France, causing weeks long delays to the Panzer units set to reinforce the German defenses. They also blew up the electricity going to the Normandy beachhead areas, which took out the Rommel designed side firing flamethrower hardpoints, set up to take out troops on the beaches. These were all electrical powered, so none were functional when the soldiers hit the beaches.
My father and uncles were all in the military at this time too, but were all in the South Pacific. My grandfather was training troops states side, but he'd done his time, as his unit had gone in to Dieppe.