As we remember operation, today I look at the how the operation was planned. The United States Army General Dwight D Eisenhower was chosen to lead the invasion of Germany. The British General Bernard Montgomery was the Allied ground forces Commander. Together the two and their staff planned an attack by the code name Operation Overlord. According to Krysa,
“The broad outline of the attack was relatively simple: find suitable beaches, gather landing force, isolate the battlefield by attacking bridges, tunnels, and rail networks so that German defenders could not be easily reinforced, and land the troops. Once a beachhead was established, the plan was to pour in the supplies needed to sustain an offensive and then break out into the French countryside.” – “D-Day” Invasion,”
Generally the plan was that on D-Day Paratroopers would be dropped into France by moonlight, the late evening or early morning before the invasion. Their task hold the bridges and roads that the Germans would want to utilise once the invasion began. The rest of the troops would land on five beaches. The British Army would land in the east on the code-named beaches Sword and Gold. The Canadians would invade Juno beach. The American Army would invade Omaha and Utah beach.”
The Allied Forces did not underrate the enemy they were facing. The Germany were well organised. Hence, the Allied Forces conducted a detailed planning and preparation in order to achieve success. The planners considered the following factors;
- Surprise of the initial assault.
- Adequate air support.
- The rapid concentration of assault formations.
- Adequate artificial harbours and improvised sheltered waters.
- Favourable force ratios in lodgement.
- Better performance of naval assault forces.
- Reduction of the German fighter aircraft strength.
- Logistics and sustaining the force over the beach for three months.
The above factors had to be present in the minds of the Allied Forces senior leadership as they prepared plans for the invasion.
Selection of Landing Sites
One of the major factors during the planning was determine where to land. Therefore, many sites had to be considered. The area of Pas-de-Calais was the ideal location for the landing. It was about 34 kilometres away from the coast of England and had a deep-water port with the shortest route to Germany. Nevertheless, the Allies did their appreciation and knew that the Germans expected the invasion to be launched precisely there. Thus, they chose the least expected five landing beaches Utah, Omaha, Gold, Juno and Sword in western Normandy about 145 Kilometres away from the coast of England. Utah and Omaha beaches were assigned to the US Army, Gold and Sword to the British, and Juno to the Canadians. The assault sector extended front over 81 Kilometres from Sainte-Marie-du Mont to the estuary of the Oren River.
These beaches were ideal since they had access to the road network around to Caen, which was a number one objective for the British and Canadian troops. This would ensure an anchor for the Allies on the Continent and accessible routes to Paris. The Normandy beaches offered suitable landing terrain as they were flat, wide and deep enough to enable thousands of men and their equipment to land. Besides, the countryside was also suitable for the construction of makeshift airfields.
The Normandy beaches were chosen since they were close to the deepwater port of Cherbourg. Cherbourg was the number one objective for the American troops, and it was impossible to be captured from the sea. It was a crucial entry point for tens of thousands of men and millions of tons of supplies and equipment needed for the push to Paris and eventually Berlin.
Another factor was the less fortified beaches of Normandy and its location south of the Seine River as compared to heavily fortified areas north of Seine River. The Allied Forces could advance across Northern France and assault Germany if sufficient supplies could be build up at Normandy.
The next consideration was when to land, and it depended on a combination of favourable conditions; full moon, a rising tide at dawn, and of course good weather.
Full Moon. For the paratroopers that earmarked para dropping after midnight to secure the flanks of the assault zone, night flying was crucial in order for the pilots to avoid the heavy concentrations of German anti-aircraft guns in the invasion area. However, a full moonlight was helpful for night bombers to find their targets as well as pilots of the airborne forces.
A Rising Tide at Dawn. The Allied decided that a dawn assault would be best and high tide would hide Rommel’s deadly obstacles from the landing craft. This would allow the combat engineers to destroy German defensive obstacles on the beach and help the vessels navigate safely through the cleared and marked channels. However, such conditions could only be met between 5th and 7th June. Another possibility of the high tide would have been ten days later on 19th June, thereby increasing the danger of exposing this secret campaign plan.
D-Day depended on suitable weather, and it was almost cancelled because of terrible weather conditions; hence, the invasion was delayed by one day. 
The Concept of Operation Overlord
Once the strategic objective was defined, and the planning factors were considered, the planners had to develop a concept of operation. As at 27th July 1943, the Concept of Operation Overlord was as follows:
‘OVERLORD’ is to mount and carry out an operation with forces and equipment established in the UK by 1st May 1944, to secure a lodgment on the continent from which further offensive operations can be developed. The lodgment area must contain sufficient port facilities to maintain a force of some twenty-six to thirty divisions and enable the force to be augmented by follow-up shipments from the United States or elsewhere of additional divisions and supporting units at the rate of three to five divisions per month.”
The Allied Forces Campaign Plan
The planners envisioned that the Allied Campaign Plan would be executed in five phases.
Phase I. The Preliminary Phase would begin immediately by setting the conditions for the major offensive in 1944. Its aim was to soften Germans resistance throughout France while keeping forces away from the intended invasion area. They would employ naval and air action, propaganda and psychological operations, sabotage and special operations, political and economic disruption.
Phase II. The Preparatory Phase would assemble the invasion force and make final strikes against German forces. The aim was to concentrate the naval task forces, load assault echelons on ships, marshal follow-on echelons at the ports and conduct final activities once the invasion was imminent and destroy the lines of communications and headquarters of mobile reserves.
Phase III. Assault Phase was the major aspect of D-Day offensive and the conduct of concentrated air and naval bombardments, airborne assaults, commando actions and the seaborne landings of forces onto France.
Phase IV. Involved the Follow Up and Build Up Phase. Its aim was to destroy enemy forces, expand the beachhead, establish a lodgment with air and seaports and increase the combat power of the forces ashore.
Phase VI. The Operation began at approximately D+14 after the quick seizure of Cherbourg due to weak resistance or stronger German resistance. The Supreme Allied Commander would make decisions based on the situation before final preparations could be made.
The Allied Naval Plan
The main aspect of the naval planning was safe and timely arrival of the assault forces at the beaches. Then cover the landing through gunfire support and shore bombardment. It also included neutralizing enemy coastal batteries with the help of heavy guns. The subsequent assigned operations were to support, maintain and the rapid build-up of the forces ashore. Since the naval operations included a considerable number of ships and landing craft, it was essential to build temporary artificial harbours till any ports are seized for assurance of continuous supply to the assault forces. The plan was also made to clear mines and beach obstacles with the help of minesweeping and specialized craft.
 MAJ Stephen S. Seitz, CDR Kelly M. Oakley and CDR Francisco Garcia-Guido bro (2002) Operation Overlord and The Principles of War.
 Educator’s Resource Guide, D-Day Normandy 1944.
 Educator’s Resource Guide, D-Day Normandy 1944
 Major John C. Krysa, 1988. Operational planning in the Normandy Campaign 1944.
 Stephen E. Ambrose, D-Day June 6, 1944. Touchstone Rockefeller Center, 1995.