In The Longest Day by Cornelius Ryan, there is a comprehensive discussion of all the factors that made D-Day a not-disaster, and some of which were a set of coincidences so downright odd that Hitler himself was convinced Allied secret service operatives had orchestrated them. But they appear to just be a set of really weird coincidences that undoubtedly contributed in no small part to the success of the invasion which had its fair share of massive screw-ups from the get-go.
1. The Luftwaffe squadrons stationed near the landing sites were randomly moved way back
By the time the invasion began, a grand total of two planes out of 183 were near enough to mount a form of air defence. The day before, three squadrons of ace fighters had been relocated purely to get them out of harm’s way whilst allied bombardment continued (as it had for months). There is no adequate explanation as to why it happened to be the exact wrong moment to move them, and the lack of air support proved decisive.
"Germany’s air force and navy could do little to resist invasion. The Luftwaffe had withdrawn nearly all its fighters to counter American daylight bombing operations over Germany."
http://www.iwm.org.uk/history/the-german-response-to-d-day
“Germany’s air force no longer had control of the skies, thus missing the chance to spot the Allied build-up on England’s southern coast––and being able to disrupt or destroy it. The Luftwaffe’s last remaining fighter squadrons in France had been moved far out of range from the Normandy beaches.
And, once the invasion was underway, the movement of the panzers and other reinforcements was stopped by Allied air power. Without control of the air, Germany was doomed.”
http://warfarehistorynetwork.com/daily/wwii/nazi-blunders-germanys-biggest-d-day-mistakes/
2. The Panzer divisions nearby were pulled back and reserves not committed
Hitler had personal command of the Panzer division stationed on alert to respond to threats. He did not commit them in time for them to have any chance of repelling the invasion. Meanwhile, the 21st Panzer division, which Rommel had stressed should be held right at the beaches in order to throw any invasion back into the sea, was instead relocated miles away beyond Caen and unable to commit to the D-Day battles. By the time they tried to get through, the roads had been comprehensively screwed up so they couldn’t get through fast enough and the allies had the high-ground. The Panzers were more or less crushed.
“Von Schweppenburg was keen to keep the armour well back, hidden north of Paris, until the Allies were committed, and then launch a mass counterattack. In contrast, Rommel feared that Allied air superiority would expose the panzers to devastating fighter-bomber attacks, preventing their movement. He wanted every tank as near to the coast as possible, where in his view the battle would be won or lost. He hoped too that the morale of the infantry manning the beach defences would be strengthened by the presence of elite formations beside them.
It fell to Hitler to decide on the matter, and typically he chose an unworkable solution. Rommel was given operational control of just three panzer divisions, only one of which – 21st Panzer – was located within striking distance of the Normandy coast. The other two – 2nd and 116th Panzer – were held north of the Seine.”
http://www.iwm.org.uk/history/the-german-response-to-d-day
“The Führer issued a directive that Germany’s armored forces, which were kept well back from the beaches, could only be deployed upon his personal order.”
http://warfarehistorynetwork.com/daily/wwii/nazi-blunders-germanys-biggest-d-day-mistakes/
3. The Fleet took a trip to Cherbourg
Because of the weather, the fleet commanders figured that there was no chance of an invasion fleet that night or the next day, so they sailed away and left the path to Normandy wide open.
”The Navy’s warships had been hounded to destruction or were bottled up in ports. Its U-boats would have an almost impossible job penetrating the belt of Allied naval and air defences.”
http://www.iwm.org.uk/history/the-german-response-to-d-day
” Except for a few isolated, daring attacks (such as during an amphibious-landing rehearsal at Slapton Sands on April 28, 1944), the German navy was absent in the English Channel, allowing the massive seaborne force to cross the Channel virtually unimpeded.”
http://warfarehistorynetwork.com/daily/wwii/nazi-blunders-germanys-biggest-d-day-mistakes/
“Due to the bad weather, the German navy canceled its usual patrol of the English Channel. Also, a practice drill scheduled for June 6 was called off.”
http://www.historynet.com/d-day-the-beginning-of-the-end-for-nazi-germany.htm
4. The Nazi high command was far from the front lines – ironically playing war games
Most of the senior commanders had been recalled far behind the lines to consider possible invasion tactics from the Allies. Rommel wasn’t even in France; he’d left for Germany. By the time the invasion began, there was a serious problem with command officers not being in place or even informed until it was far too late. And by then the Resistance had been blowing up the communications and railways, making command coordination a much harder task than it should have been.
“A number of key German commanders were absent from their posts during the critical first hours of June 6, 1944. Believing that the Allies would not invade during a violent Channel storm on June 5, Admiral Theodor Krancke, the naval commander in the west, was on his way to Bordeaux. Maj. Gen. Edgar Feuchtinger, commander of the 21st Panzer Division, was heading to Paris to see his mistress; the commander of the Merville Battery on the far eastern flank of the invasion area was in bed with his.
Field Marshal Erwin Rommel had left Normandy for a trip back to Germany for his wife’s 50th birthday; General Friedrich Dollmann, commanding the Seventh Army in Normandy, had left his headquarters to attend a war-games exercise at Rennes––over 100 miles south of the Normandy coast. Lt.. Gen. Heinz Hellmich, commander of the 243rd Division, was heading there, too, as was Maj. Gen. Wilhelm Falley, CG of the 91st Air-Landing Division.”
http://warfarehistorynetwork.com/daily/wwii/nazi-blunders-germanys-biggest-d-day-mistakes/
” Things got no better for the Wehrmacht as the day wore on. The landing had come as a complete surprise, and many German commanders were away from their posts. Rommel was spending a day back at home, celebrating his wife’s birthday. Hitler, as was his wont, was sleeping in. General Friedrich Dollmann, the Seventh Army commander, had scheduled a planning war game in Rennes, testing responses to an Allied landing. His division commanders were on the road to Rennes, got the recall en route, and spent the morning scurrying back to their command posts. General Wilhelm Falley of the 91st Air-Landing Infantry Division could clearly hear the roar of thousands of Allied aircraft engines in the night sky. He turned his car around and raced back to his headquarters near Bernaville. As he pulled onto the grounds, however, Falley ran into a blaze of gunfire from U.S. paratroops of the 82nd Airborne Division. He became the first German general to die in Normandy.”
http://www.historynet.com/d-day-german-lens.htm
5. The Alert went out to the whole German army – except the one in Normandy
When German intelligence picked up the coded messages warning the French of the invasion, they immediately told the commander of the Western Front. He wasn’t particularly impressed, saying he was too old to be excited by what could be a diversionary assault. However, he formally put the defensive armies along the coast on alert, all except Group B, the Seventh Army. The one holding Normandy, where the invasion was about to begin. There really is no reasonable explanation for that oversight, unless it was intentional, and whilst it is known that Field Marshal Von R had contempt for Hitler (called him “that Bohemian corporal”), it isn’t likely he intended to hinder Germany’s chances. And yet, the Seventh was not alerted, and was caught off guard.
“At 8.15 p.m., the second half of Verlaine’s poem (“Bercent mon coeur/D’une langeur monotone – “sooth my heart with a monotonous langour”) is broadcast by the BBC as a coded message to the French Resistance. The German military intelligence service (the Abwehr) is aware of the message’s significance and also hear it. They pass an invasion alert on to various headquarters, including that of the German 15th Army (based in northern France). However the German 7th Army in Normandy is not alerted.”
http://www.ddaymuseum.co.uk/d-day/countdown-to-d-day
6. Hitler was asleep.
Any reasonable person would expect that Hitler would be informed the moment a ship was spotted making for France flying British colours. As the man who demanded total control over the war theatre, who took personal command of the German forces and dictated how to fight battles to men far, far more qualified than him, he surely would have been told no matter what? But no. The invasion began early in the morning, after pathfinders and paratroopers had been landing all over Normandy for hours, and reports of gliders landing vehicles and guns had been coming in since 3am. The troops were landing by 8am. And Hitler wasn’t even awake until 10. He was informed at 10.30, and by then the chance to crush the invasion with a carefully coordinated response was well and truly gone. The reason given was that the night reports were inconclusive, that the prevailing view was that the invasion would not be that night because of the weather, and that the invasion would not be in Normandy because a Calais landing was far more likely to succeed. None of it really explains why Hitler wasn’t even woken up, and it almost certainly contributed to Germany losing the war.
“Compounding the situation, Hitler had gone to bed late on June 5 and gave orders that he was not to be awakened for any reason. His staff obeyed that order; by the time Hitler woke up, it was too late to stop the invasion.”
http://warfarehistorynetwork.com/daily/wwii/nazi-blunders-germanys-biggest-d-day-mistakes/
“ The two army groups each got three panzer divisions to deploy as they wished; Panzer Group West, a central reserve under the command of General Leo Geyr von Schweppenburg, got the other four. The authority to send them into action, however, lay with the High Command of the Armed Forces (Oberkommando der Werhmacht, or OKW)—that is, with Adolf Hitler himself. With their limited resources, the Germans had tied themselves in knots…Hitler, as was his wont, was sleeping in.”
http://www.historynet.com/d-day-german-lens.htm
“The only high-command officer who responded correctly to the crisis at hand was Field Marshal Rundstedt, the old man who was there for window dressing and who was so scorned by Hitler and OKW. Two hours before the seaborne landings began, he ordered the two reserve panzer divisions available for counterattack in Normandy, the 12th SS Panzer and Panzer Lehr, to move immediately toward Caen. He did so on the basis of an intuitive judgment that the airborne landings were on such a large scale that they could not be a mere deception maneuver (as some of his staff argued) and would have to be reinforced from the sea. The only place such landings could come in lower Normandy were on the Calvados and Cotentin coasts. He wanted armor there to meet the attack.
Rundstedt's reasoning was sound, his action decisive, his orders clear. But the panzer divisions were not under his command. They were in OKW reserve. To save precious time, Rundstedt had first ordered them to move out, then requested OKW approval. OKW did not approve. At 0730 Jodi informed Rundstedt that the two divisions could not be committed until Hitler gave the order, and Hitler was still sleeping. Rundstedt had to countermand the move-out order. Hitler slept until noon.”