D-Day: What Factors Were Considered When Planning Operation Overlord

View from a Higgins boat

Most of the world recognizes June 6, 1944, like D-Day, World War II's pivotal event. Novels and motion pictures have portrayed the massive invasion as Allied troops storming the beaches amid a German firepower hail before progressing beyond the German lines, through France, and ultimately to Berlin. In essence, that is exactly what transpired. However, the actual event was a massive and complex series of engagements that occurred in three stages; the break-in, the buildup, and the breakout. If any of these phases were unsuccessful, Operation Overlord would have failed, and the outcome of the Second World War would have differed greatly. To fully comprehend the three stages of the attack, the operation's planning must first be understood.

The Teheran Conference

The "Big Three" at the Teheran Conference, November 1943. (l-r) Stalin, Roosevelt, Churchill.

Soviet leader Josef Stalin was clamoring for the Allied invasion of Europe since early 1943. To relieve some of the pressure in their battle with Germany, the Soviet Army needed its allies to engage Hitler’s army from the western side of Germany’s border. By opening a second front in Western Europe, Germany would be forced to re-allocate troops, supplies, and equipment from their battle lines on the east, thereby affording the Soviets a slight reprieve in their tenacious battle the Germans. However, British Prime Minister Winston Churchill was adamant that the Italian and Mediterranean campaigns retain the highest priority. The United States President Franklin Delano Roosevelt was also hesitant of a 1943 invasion as German U-boats continued to fiercely patrol the Atlantic Ocean.[1]

The submarines, which patrolled either singly or in a group known as a “wolf-pack,” wreaked havoc on U.S. shipping until the spring of 1943, thereby creating shortages in England supplies, equipment, landing craft, ships, and troops. F.D.R. and Churchill maintained that due to the German submarine attacks on Merchant Marine vessels, there were not enough men and equipment to forge such a massive invasion. There is a debate in the scholastic world as to whether it was possible and feasible for the Allies to launch the invasion in 1943 and end the war that much sooner. Some historians support the logic of Churchill and F.D.R. in that the shortages were too great and that the Italian campaign was affording much-needed experience to untried soldiers, especially the Americans. Conversely, others aver that in 1943 Germany was much weaker than in 1944, and by delaying, Hitler had time to build up troops and supplies. Arguably, the Allies' limited resources were adequate to wage a victorious campaign against the equally weak German Army. In 1943, there were forty-nine second-line German divisions stationed in France. By 1944, additional armor and nine divisions of men were added.[2] To agree on the specifics of the invasion, “The Big Three,” Roosevelt, Churchill, and Stalin met together for the first time in November 1943 at the Teheran Conference.

At this historic meeting, the three Allies, at last, agreed that the European invasion was to become the top priority in the war. The late spring of 1944 was chosen to provide time for the commanders to formulate a strategy and train the troops who were designated to carry out the mission. American General Dwight Eisenhower was designated as the supreme commander of the Allied Expeditionary Forces. British General Bernard Montgomery was charged with the command of all Allied ground forces. Over the remainder of 1943 and deep into spring 1944, troops and supplies began to amass in England.

Why Normandy?

Field Marshal Gerd von Rundstedt.

Normandy was not a port city, thereby making a great amphibious invasion cumbersome and problematic. Cherbourg and Le Havre, west and east of Normandy, respectively, were considered and quickly declined as options for the invasion. Although these were port cities and thus would have facilitated the landings, these very reasons made them obvious choices, thereby affording Germany to mount an impregnable defense. Another accommodating site was Pas de Calais, as it was just twenty miles from England's coast. This is where the Germans expected the landing to take place and amassed defenses on Calais' beaches accordingly. The Allies discovered this through their decoding system known as Ultra and used this knowledge to their advantage. The German commanders, except Hitler, did not consider Normandy a feasible site as it lacked ports to accommodate landings and create a supply line. Field Marshal Gerd von Rundstedt, commander of all German forces in Western Europe, and Field Marshal Erwin Rommel, the ground forces leader, both believed Calais was the target.

To further the German belief that Pas de Calais was the invasion site, Eisenhower ordered General George Patton to Southeast England. Through a spy network, made sure the German commanders were aware of Patton’s presence. A full-fledged “phony army” was constructed, complete with armor, barracks, and men. To further their deception, all bombing runs before the invasion avoided Normandy and focused on supply and communication facilities in other port towns. This ruse worked wonderfully for the Allies as the German Army made preparations in and around Calais.

Field Marshal Rommel took nothing for granted and ordered the build-up of an Atlantic Wall at every possible landing spot. Rommel’s plan exhausted an immense amount of resources, including more than four million mines set all along the beaches of France. Bunkers and casements housing .155mm guns were constructed. Most importantly, Rommel ordered numerous underwater obstacles, realizing that to avoid the obstructions, the Allies must land at low tide. This enabled Germany to calculate the invasion's time as low tide occurred at dawn only a few days each month.[3]

Field Marshal Erwin Rommel.

Rommel and Rundstedt were satisfied with their defenses and were still certain Calais was to be the invasion site. However, Hitler continued to focus on Normandy. To appease him, the two commanders added defensive reinforcements at Normandy. Rundstedt and Rommel had several disagreements in strategy and tactics. The most grievous for the German Army was Rundstedt’s decision to overrule Rommel’s plan to keep tanks and reserve troops close to the beaches. Rommel strategized that it was most pragmatic to halt the Allied advance immediately on the beach. Simultaneously, Rundstedt felt the defenses were adequate and that the armor and soldiers would be most effective if held in reserve. This proved to be a great error on the part of Rundstedt as the divisions deployed on the beaches were second-rate with little experience. Reinforcements with armor may have halted the invading troops. An additional problem for the German Army was that the Allied forces controlled the airspace along the coast of France, affording them air cover for the invasion.


Rommel inspecting barriers along the beaches of the Atlantic Wall.

Rather than either combatant, Earth's environment was to dictate terms as to when the invasion would occur. The Allies and Germany were all well aware of the conditions that needed to be met. Because of the obstacles, low tide was a must. Additionally, the navy bombers required good visibility and calm seas to provide pre-invasion bombardments and cover fire. Lastly, and perhaps most importantly for the Allies, a late-rising moon was imperative as they planned a pre-invasion airborne mission. Paratroopers of the 82nd and 101st Airborne divisions were ordered to drop behind the German lines before the invasion. With the aid of the French underground network, their mission was to secure roads and bridges and cut German lines of communications. To accomplish this, the timing of the moon rise was crucial. The optimal moon, weather, and tidal conditions occurred synchronically only on the 5th, 6th, and 7th of June.[4]

Eisenhower initially chose June 5 as the date for Operation Overlord. The mission was scratched for that date as a storm rolled in that caused poor visibility and choppy seas. The storm was forecast to last several days; therefore, the German high command was certain the invasion would be held back until July. Taking advantage of the storm, Rommel returned to Germany to attend his wife’s birthday party, and several other commanders followed similar routes away from the beaches. However, an Allied meteorologist predicted there would be a break in the storm for a period of several hours, affording Eisenhower a brief window to carry out the mission between the wee hours of the morning until approximately noon on June 6, 1944.


General Eisenhower took advantage of the break in the storm and ordered Operation Overlord to commence. To reach Berlin and at last break the formidable German Army, the second front in Western Europe was imperative. The Italian campaign was progressing in favor of the Allies. However, the German’s fought ferociously in their retreat and slowed the Allied advance considerably. Stalin’s army kept the German soldiers at bay, yet the carnage was horrific, and the Soviet soldiers and partisans were exhausted and starving. The Teheran Conference set in motion the greatest amphibious invasion in history to open a second front and force the German Army to split its forces. By doing so, the weakening Germans faced their enemies on two fronts, thereby diminishing their forces' concentration.

Planning the invasion was a tactical and strategical task of the highest order. For the Allies to succeed, precise and coordinated missions needed to be executed in the face of German defenses. As the Reich’s army held the high ground on the beaches and the armada could be easily seen moving across the English Channel, Eisenhower and his generals feared the carnage would be great; and it was.


  1. Michael J. Lyons, World War II: A Short History, 5th ed. (Upper Saddle River, NJ: Prentice-Hall, 2010), 246. For an excellent account of the discussion of a second front in 1943, see Walter S. Dunn, Second Front Now ̶ ̶ ̶ 1943 (University of Alabama Press, 1980).
  2. Lyons, 246.
  3. Lyons, 248-49. For a detailed reading on Rommel’s defensive plans, see Samuel W. Mitchum, The Desert Fox in Normandy: Rommel’s Defense of Fortress Europe (Westport, CT: Praeger/Greenwood, 1996).
  4. Stephen Toth, “Total War and Crisis” (lecture, Arizona State University, Glendale, November 17, 2011).

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