The history behind Operation Overlord started as early as the evacuation of Dunkirk in 1940 when Winston Churchill realised that an invasion of ‘Fortress Europe’ would be needed if Hitler was to be expelled from France and he ordered that planning should start with due speed.

The Russians, led by Joseph Stalin, had also been calling for a second front as early as 1941 when Germany’s blitzkrieg onslaught against Russia was at its peak.

Regardless of this, no steps were taken to start the planning for Overlord until the war meeting at Casablanca. This was primarily because the world’s most formidable military power, America, had campaigns in the Far East to occupy her mind and Britain would need to bring America on board for any discussion about a European invasion – let alone the actual planning for one.

At Casablanca, it was decided to set up an Allied Staff to plan for the operation under a Chief-of-Staff to the Supreme Allied Commander (COSSAC). The first person to hold this title was Lieutenant General F E Morgan. At the Washington Conference in May 1943, it was decided that total priority should be given to Overlord. A tentative date – May 1944 – was set.

In May 1943, the Allies met at Quebec and COSSAC produced its first outline plan.

The first issue that COSSAC had to address was where a mass landing would be. The two choices were the Pays de Calais or Normandy east of the Contentin Peninsula.

The Pays de Calais had a number of advantages identified by COSSAC. It was the shortest route so any crossing would be the quickest; it would give fighter planes a maximum time in the air and bombers could easily attack the area. However, the very lack of distance had been identified by the Germans and they had built massive fortifications all around the area. COSSAC believed that the German defences here were especially potent. Another identified weakness was that the prospective attack would have to be launched almost solely from Dover and Newhaven and it was believed that neither port was capable of handling the sheer numbers envisaged by COSSAC. Portsmouth and Southampton could play a part but they were effectively too far away to have a full role.

Normandy was also a possibility but COSSAC recognised that the distance would be a serious issue in that the weather could quickly change during a long crossing creating mayhem. However, the invasion force was better served by Portsmouth, Southampton, Poole and Portland, which could accommodate a large force. It was also believed that the German defences were weaker in Normandy when compared to the Pays de Calais. Despite the fact that any aerial support would include ‘dead’ flying time, this was felt a necessary sacrifice. Therefore, Normandy was chosen.

COSSAC, as a result of limits placed on it by the Combined Chiefs-of-Staff, had also planned on a limited invasion force that would require just three beaches. The rationale for this was a shortage of landing craft as so many had been taken up in the war in the Far East. Morgan planned for an invasion force landing at the eastern base of the Cotentin Peninsula. Morgan envisaged an invasion by three seaborne divisions supported by two airbourne divisions. Two more seabourne division would immediately follow-up with a total landing force that comprised of 18 divisions.

In November 1943, Churchill and Roosevelt met in Cairo. Here the main outlines of the plan were settled and, more important, the command structure was settled.

Dwight Eisenhower was made supreme commander of the invasion force and Air Chief-Marshall Arthur Tedder was made his deputy. General Walter Bedell Smith was chosen as Eisenhower’s Chief of Staff. Two army groups were also created. One, an American one, was to be commanded by General Omar Bradley. The British one was commanded by Bernard Montgomery. ‘Monty’ was also given command of all land forces during the assault phase in Normandy. Admiral Bertram Ramsey, who had overseen the Dunkirk evacuation, was to be in command of all naval forces. The naval forces were again split in two. The American one was commanded by Admiral Kirk and the British one by Admiral Vian. The Allied air forces were commanded by Air Chief Marshall Leigh Mallory; the British contingent was commanded by Air Marshall Coningham and the American by General Brereton.

The actual team was an extremely good mix of experience and military success, which bode well for Overlord.

By January 1944, all the commanders were in Britain, which allowed for detailed planning to start. The command team quickly reached one conclusion. To be successful, a much bigger target area had to be selected and many more men had to be involved from day one of the invasion. Eisenhower believed that the capture of Cherbourg was vital if the Allies were to be able to supply their men with all that they needed for a successful advance across France. Eisenhower envisaged an attack on five beaches and that each beach should be attacked by a national unit; therefore, command structures would not be unnecessarily complicated as each would be used to their own routines. That is why the five beaches assaulted were given over to two American units (Utah and Omaha), one to the Canadians (Juno) and two to the British (Sword and Gold). Eisenhower also wanted a total of 16 divisions landed in Normandy within a fortnight of the first landing. Eventually, Eisenhower wanted a total of 23 divisions to be landed at Normandy.

Eisenhower’s requirements had two problems. If the first assault was not successful in pushing the Germans back and reinforcements were being brought in, would chaos ensue on the beaches as they became overcrowded with personnel? Secondly, with such a vast force, where would all the landing craft come from? The date for Overlord was pushed back to the end of May to allow for the building of more landing craft. Eventually just enough landing craft were available for the sea crossing (code-named Neptune) to take place on June 6th 1944.