When did the Germans realize the D-Day landing was the real invasion and not a diversion?

by Dion Osika

Editor's note: 'Scout' recently posed the above question on the CombatFan discussion group when noting some discrepancies among opinion of the Germans as presented in the films "The Longest Day" and "Patton." Below is a response by Dodger (aka Dion Osika) regarding the German High Command and D-Day. We thought you might find his analysis interesting.
— Jan 04, 2003

Dodger here ...

First of all, the sequence of events you described are reasonably accurate and in correct order. What movies fail to explain to us is usually all the whys that influenced the decisions made by the historical characters.

Patton and Operation Fortitude

The German command always believed that the Allies had more men (divisions) and naval forces available. This was brought about by a massive failure of their intelligence network and by the Allied deception plan, Operation Fortitude. The Allies set up Patton to command the nonexistent First Army Group, which the Germans were to believe would be the main Allied effort in the invasion of France. As long as Patton was still in England, the Germans would have a reason to believe that the Allies were capable of launching an additional invasion effort somewhere.

Each command level would interpret the invasion slightly different from another. For example, a German sergeant at Omaha Beach would absolutely believe the invasion was the real one, not a diversion. Whereas, the commander of the forces in the West, Field Marshal von Rundstedt, would wait and consider his sources as to whether Normandy was a diversion or not. In addition, if he felt that the Allies had more troops and ships available for another landing, he would always hold back some reserves and not entirely strip away his defences.

Pas de Calais

The Pas de Calais was always considered to be the most direct route to Germany, as well as containing many ports which the Allies needed. It would not be stripped of units unless there was a zero percent possibility of another invasion. Even after the German army collapsed in Normandy,
the Germans along the Pas de Calais and in the ports did not leave. The Canadian Army spent the best part of September 1944 rooting them out.

Germans Attempt to Contain the Invasion of Normandy

Soon after the Normandy landings, the Germans began to move mobile units (panzer divisions) into the beachhead area to contain the invasion forces and push them back. These units were attached to different levels of command and required approval by higher commanders. For example, 21st Panzer was stationed around Caen and under 7th Army control and immediately was put into action on D-Day. Other panzer units, 12th SS and Panzer Lehr were further away but under a higher authority level. They were released for action and moved to the beachhead on D-Day, but other units still were held in reserve. This continued for weeks after the invasion, as the Germans would release units in hopes of containing the beachhead, but keeping reserves available in case of additional landings.

The success of a seaborne invasion requires that the sealift capability of the assaulting force is capable of building up forces in the beachhead faster than the defending force can build up a defending or counterattacking force. The Allies gave themselves a slight edge by always threatening to make additional landings, thus keeping the Germans from moving all of their reserves into the beachhead. The Germans stripped units from Brittany, Pas de Calais, Southern France and even Norway in an attempt to build up reserves. They arrived in driblets and were not committed in large numbers. The panzer units, which were to be used as mobile reserves, were worn down in the front
lines containing the unrelenting Allied pressure. BTW, most of the panzers were committed in the British sector because the Germans feared a breakthrough in that area would collapse their entire line.

Allied Stagnation after D-Day

The Allies were hampered in their build up as well. In order to bring in troops and supplies, they needed a port. Cherbourg, at the northern end of the Cotentin peninsula was a first priority for the US forces. After establishing a firm beachhead, the US forces moved west across the base of the peninsula to isolate the Cherbourg garrison. Once across the peninsula, the US Army sent divisions north to Cherbourg but had to maintain units facing south as well to prevent any German reinforcement.
They didn't have enough manpower to attack south and north at the same time. Once Cherbourg was captured the divisions could redeploy for action in the south. Unfortunately, the Germans thoroughly destroyed the port of Cherbourg and it would not be put into use for months.

The Allies also built two artificial harbors, called Mulberry, to bring in supplies and troops. Several weeks after D-Day, a fierce storm destroyed the US Mulberry and damaged the British harbor. This further slowed the Allied buildup and was part of the reason that the Allies had a slow and difficult
advance into the hedgerow country.

By early July, the stagnant situation in Normandy was becoming serious. Moral and public opinion was down, causing many to fear a repetition to WWI style trench warfare. Enough US divisions had arrived in Normandy, and Gen. Bradley developed the Cobra Operation to achieve a breakthrough.

Patton and Operation Cobra (breakout)

Although Patton was sidelined during the opening phase of the Normandy invasion, it was always part of the plan to split the US forces into two armies and place one under his control. Bradley would move up one step to command 12 U.S. Army Group and Gen Hodges would take over Bradley's First Army Command. A U.S. Army was normally composed of two, sometimes three Corps, each with 3 divisions. By early July, 1st Army had four corps attached and it was necessary to achieve a breakout so that Third Army could be 'activated.'

The units that would come under Third Army were already in Normandy, it was just a transfer of the command structure that would give birth to Patton's command. Patton had come to Normandy in early July, but this was kept secret in order to allow the Germans to think that he was still waiting in England
to launch another invasion. The plan was to transfer command of Patton's fictitious First Army Group (FAG) to Gen. Leslie McNair, who was the next ranking officer under Gen. Marshall. This command change hoped to keep the Germans believing that FAG was still a strategic threat.

Operation Cobra had been postponed due to weather and other reasons by almost one week. It was scheduled to start on July 24th with a massive aerial carpet bombing along the German front lines. The weather was poor on that date, and a recall order was issued, but several bomber groups did not receive the order and bombed the target. Unfortunately, some groups dropped incorrectly due to smoke and haze and many US soldiers were killed. The operation was rescheduled for the next day and, again, bombs fell on U.S. troops. Among those killed was Gen. McNair, and his death was kept secret to keep the Fortitude plan alive. His funeral in Normandy was attended by 3 or 4 other
officers.

As Cobra and the penetration of the German front unfolded, Patton assisted in movements along the western Cotentin. On August 1st, after the fall of Avranches and breaking into Brittany, Bradley executed the change in command and Third Army assumed command of units that had previously fought under First Army. However Patton was not mentioned in the press until several weeks
later as the breakthrough turned into a pursuit phase of operations.

The Fog of War

All through this time the Germans were trying to guess when and where the Allies may launch another sea landing. In fact, in mid-August the Allies landed in Southern France and once that occurred the Germans literally ran for the Rhine River. Trying to guess an enemy's strength and intention introduces many unknowns, and this is sometimes referred to as the fog of war. Incomplete, erroneous, or no information leads commanders to make best guesses to fight a battle.

As a simple analogy, most of us know how the game of chess is played. Each side has the same number of pieces, we know the movement and power of each piece and we can see the location of each one on the board. Introduce a simple concept to illustrate the fog of war by playing chess while being able to see only the squares that are occupied by the opponent. We can keep track of the chessmen on our side and where an opponent piece may occupy a square, but we don't know if that piece is a pawn or a bishop. It places a different perspective on playing the game.

This is why as readers of history we see some simple answers, but at the time the commanders in the field could not see the situation in the same light.

Military Surplus for Less Dodger out...