What is D-day?

D-Day took place on June 6, 1944 and was the largest military invasion ever. On that day 156,000 Allied troops were deployed. They crossed over from southern England to Normandy. There they had to establish a bridgehead (a foothold) by means of airborne and amphibious landings.

In addition, the Allied landings in Normandy were the beginning of Operation Overlord. A major undertaking resulting in the eventual liberation of Western Europe.

Also, the term ‘D-Day’ was originally used to herald the beginning of a major operation.

The Normandy landings were the first, largest and most important invasion of the Second World War for the Western Allies. Concluding from these three factors, this is probably the reason why we consider this moment as D-day.

Why D-day?

There were many reasons why this day had to take place.

The main reason for the development of D-day was the need for a second front in Europe. The Germans had invaded the Soviet Union in 1941. As a result, they had to withstand the pressure in Eastern Europe almost alone. Consequently, a new front had to be opened in Western Europe. This was what the American president Franklin Roosevelt and the British prime minister Winston Churchill had promised Stalin. This promise would determine the further course of World War II.

Preparation for D-day

The preparation for D-Day consisted of several facets. These had to ensure that the chance of an Allied victory was guaranteed.

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The planning for D-day

The initial plans by COSSAC

The firm foundations and the original plans were laid by COSSAC (Chief of Staff to the Supreme Allied Commander). This consisted of Frederick E. Morgan and his Allied staff.

Quebec Conference

COSSAC presented the preliminary plan at the Quebec Conference. The plan: the landing was done by three divisions from the sea and two regiments from the air.

The final plans

The plans for D-Day were presented in their final form under the supervision of SHAEF.  (Supreme Headquarters Allied Expeditionary Force)

Targeted bombing

There were many strategic bombing raids on airfields, factories and transport links. This was done to limit the German striking power towards the invasion area of Normandy.


Besides all other plans, spies and operations were also called in to mislead the Germans. This with the intention to keep them wondering as long as possible where and when the invasion would take place.

Artificial harbours

The Mulberry artificial harbours were ingenious structures of immense size and complexity. These floating harbours provided the necessary port facilities during the invasion of Normandy. They remained in service until the launching of the port of Cherbourg.


The men and their equipment also had to be prepared. This included the Braunton Burrows, Exercise Tiger and Exercise Fabius. The final landings were simulated as well as possible.

Preparation of the Germans

The Germans also knew that they had to prepare for a possible Allied invasion of Western Europe. Yet there were many uncertainties. Among other things the ignorance of the landing spot and the positioning of the Panzer reserves worried many German commanders.

Also in the months before the invasion, they worked with all their might to reinforce the Atlantic Wall. In many regions, the coastal defences proved rather limited. Therefore Erwin Rommel, after his experiences, gave the order to optimise the defence system as much as possible. However, there was not enough manpower and material available to complete the Atlantic Wall in time.

The date for the landings

On May 1, 1944 the Supreme Command set the target date for the landings. Eisenhower decided on May 8, in consultation with the other commanders, to postpone this date by one month. This gave extra time to produce extra landing craft. It also gave the opportunity to expand the originally planned attack with two army divisions to five.

Next, Target-date or Y-Day, the day on which D-Day had to be determined, was set on June 1. The invasion had to follow as soon as possible. As soon as possible meant on: Y + 4 (June 5). However, they postponed the landings by one more day because of bad weather conditions…

The weather

The weather forecast for D-day played a crucial role in determining the chances of success of the invasion. The meteorologists made, on June 3, 1944 in the evening, their analysis. This analysis contained several depressions. This caused great concern for the supreme command. In the morning of June 4, the different meteorologists contradicted each other. Eisenhower was already thinking of postponing the invasion until June 7.

Then, Sunday night on June 4, came an analysis of the weather team, led by James Stagg. Two depressions had merged into one layer just northwest of Scotland. It was clear that the cold front would pass over the Channel area and the invasion beaches on Monday afternoon June 5. Therefore the conditions for the landing on Tuesday morning June 6 were better than initially estimated.

Let’s Go

The next morning – June 5, 1944 at 4.30 am – General Eisenhower proclaimed the legendary words: ‘Ok, lets go’. With these three words he made history. Eisenhower made one of the most important decisions of not only his, but others’ lives.

The moment had arrived. D-day would take place on June 6, 1944.

D-Day landings

One of the largest invasions, consisting of airborne and amphibious landings, in military history.

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Airborne landings

Three divisions carried out the airborne landings that took place during the night of June 5 to 6. This was mainly to protect the flanks of the amphibious landings.

The British airborne landings with the 6th Airborne Division took place east of the amphibious landing zones. Their objective was to secure the bridges of the River Orne, communications lines and to take out the Merville Battery.

The American airborne landings took place with the 101st and 82nd Airborne Divisions west of the amphibious landing zones. Their main objective was to capture communication lines and bridges.

Amphibious landings

The amphibious landings on D-Day can be divided into five zones or beaches. On each of these beaches divisions were assigned, each with a target.

The British were assigned Sword beach and Gold beach. The Canadians Juno beach.

The Americans were assigned the beaches Omaha Beach and Utah Beach. Especially on Omaha beach the most casualties fell. The German defence was much more stubborn. The landings on Utah beach went without much trouble. In the meantime, the American rangers had the objective to destroy six guns at Pointe du Hoc. These guns could reach both Omaha and Utah beaches.

Result of D-day

For many it was one of the longest but most important days this war has known. The outcome of the Allied landings partly determined the fate of Europe.

Even though the Allies had achieved few of their objectives on 6 June, they created a bridgehead there.

Operation Overlord had begun and Allied forces could begin their liberation march across Western Europe.

Operation Overlord

Although the landings were over, many difficult undertakings followed. Operation Overlord began with these landings and would continue until the liberation of Paris.

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The start of Operation Overlord

Ultimately, the landings on June 6 were just the beginning. Next came a more difficult battle against the determined German defenders and the stubborn Normandy hedgerow landscape.


In the first place, the following objectives had to be achieved within the forty days:

  • First, to establish a bridgehead, including the towns of Carentan, Saint-Lô, Caen and Cherbourg. Cherbourg was especially important because of its harbour.
  • Then break out of the bridgehead to liberate Brittany and the harbours along the Atlantic coast. Then advance further, with a frontline that would run from Le Havre via Le Mans to Tours.
  • Eventually, after three months, the proposed area had to be taken. That area had to be bounded by the rivers Loire in the south and Seine in the north-east.

The breakthrough

As soon as Cherbourg was conquered, the Allied advance began to stagnate. This was mainly due to the enemy gradually organising itself. The American forces had great difficulty in advancing to the south. The British troops, after the capture of Caen, also had difficulties to break through to the south.

As a result, the advance had to be revived. Therefore, the Allies launched Operation Cobra. This operation forced the Americans to break through to the south. The British also supported this breakthrough. So they chose to abandon their march to the south and help the Americans in the west. The support of the British was called Operation Bluecoat.

As a result of this breakthrough, the Germans could only retreat via the east, south of Caen. Then they were surrounded and the gap threatened to close at the town of Falaise. Consequently, this retreat was later named ‘Falaise pocket‘.

The end of Operation Overlord

On August 25 Paris was officially liberated from the German occupiers. The liberation of Paris also marked the end of Operation Overlord. In short, the Allies fought an unprecedented battle for three months in this small but important part of Europe. This allowed the Allied troops to continue the beginning of the liberation through Western Europe. Later on, the British and Canadian troops moved mainly to the north. Likewise, the American troops moved eastwards towards the German border.