Was this ever a real possibility? I've heard that the German forces in the northern French coast were very weak and this was compounded by the confusing German command structure in the area. However I also read that the Allies had a helluva time getting past Omaha Beach and that the hedgerows further inland held the Allies up for months so the Allies still had plenty of problems. Was it ever a real possibility that Overlord would in fact fail?
While you wait for a more targeted answer, there is a good amount of background information present these threads from the FAQ section on “Operation Overlord aka D-Day:
German Disposition
How much of a difference would the Panzers in France made during D-Day if they were put to use earlier? - 6 comments, over 2 years old.
The commenters discuss the various obstacles that the German's faced in using their armor to oppose Operation Overlord.
Why didn't the German forces better utilize their naval assets (u-boats) to destroy troop ships while crossing the channel on d-day? - 9 comments, over 8 months old.
The commenters here talk about the historical position of German naval power as well as the immediate problems the German navy faced in 1944.
How much warning did Germany have of the D-Day invasion? - 11 comments, over 6 months old.
The commenters here give a breakdown of the German intelligence picture in the immediate runup to the invasion as well as a chronology and analysis of the actions of German commanders in France before and during the invasion, most notably Erwin Rommel.
Did the Allied Forces have complete air superiority over Northern France during D-Day? - 53 comments, over 2 years old.
The commenters here give a rundown of the material, personnel, and logistical constraints that afflicted German forces on the eve of the invasion.
Do we have an account of Hitler's personal reaction to the D-Day invasions of Normandy? - 11 comments, over 1 month old.
The commenters mostly discuss the reaction amongst German forces in France and conclude with the Hitler's unimpressed reaction further down.
D-Day invasion: Why did they select those beaches for the amphibious assaults? - 11 comments, over 9 months old.
The commenters give links and short summaries of online sources and also discuss the distribution of air cover throughout Europe during the invasion.
How much of a role did battleships play in D-Day? - 4 comments, over 1 year old.
As the title says, the commenters talk about naval fire support during the landing and also give a quote from the German "Commander in Chief in the West" about its effects on German forces.
Why did the Germans believe the Allied invasion would take place in Calais, and not Normandy? - 7 comments, over 7 months old.
This thread discusses various locations that the German's believed the Allies would land at due to both geography and the Allied counterintelligence campaign.
How did the Allies "hide" all the ships from German reconnaissance? - 2 comments, over 7 months old.
Despite the title and lack of the comments, a commenter talks about the effects of attrition on German air forces in relation to their reconnaissance capabilities.
German fortifications in Normandy at the start of the Invasion of Europe, 1944. - 11 comments, over 1 year old.
The original poster asks for books to read about the Atlantic Wall and commenters oblige them.
Related Threads
What was the back up plan if d-day failed? - 54 comments, over 5 months old.
The topmost comment gives a detailed summary pulling from both primary and secondary sources while a top level comment below it spurs a discussion on a counterfactual scenario on if the German forces could have defeated the Allied invasion.
Were there contingency plans in place in case the D-Day invasions had failed? - 8 comments, over 8 months old.
The commenter here discuss the counterfactual of the Western Allies' failed invasion while the Soviet forces on the Eastern Front progressively push through Europe.
Operation Overlord - 6 comments, over 2 years old.
Various book sources are given here, including the US Army's official history which is available online.
Are there any good interviews or accounts from German soldiers who defended against the D-Day landings? - 4 comments, over 5 months old.
One online source is linked to and a book source is given.
The correct answer here is maybe. The biggest thing that could have helped the Germans would have been to place their mass of troops at Normandy and not Calais. Hitler was completely hoodwinked by British intelligence. But keep in mind, even if they had done that, British intelligence would have likely known, and the allies would be more adequately prepared, even if they had to delay the invasion.
Omaha beach has been burned into the American mind as historically difficult fighting, as it was. But the British and Canadian beaches were taken quite easily, due to air strikes that softened up the beachhead. Omaha was supposed to be hit as well, but low cloud cover paired the targets. Regardless, a beachhead was established in both scenarios.
Next you have to consider the status of the German reserves and the paratroopers. The paratroopers had actual objectives to take, but the incredibly large drop zone (again due to cloud cover), prevented the troopers from doing anything except cause chaos in the German rear. Because of this, german officers didn't know what was going on, and held back their reserves.
All of these factors combined led to a strong allied foothold on the beach, which allowed for further forces and equipment to be ferried over. At this point, Germany would have had to commit considerable forces to push the allies off the continent, forces that he could not take from Russia or Italy.
The hedgerows were particularly frustrating for the allies, but the Germans could never stop the allied advance, only slow it down. Also keep in mind that if the Germans were to try and push the allies out of the hedgerows, they would have been met with similarly frustrating resistance.
I'm short, the answer is maybe if Germany had done everything right, as well as commit forces from other fronts, the western allies could have been pushed back into the ocean. But the landing would have been repeated, and Germany's tenuous position on its two other fronts would have been further compromised.