The rescue of most of its expeditionary force from France during the Battle of Dunkirk in early June 1940 put England in a position, both morally and in terms of manpower, to withstand the Battle of the Island against the German Luftwaffe and thus avert Hitler's threat of invasion.
Immediately after the armistice between Germany and France on June 22, 1940 - the following night - "British commandos made a reconnaissance advance on the French coast at Boulogne." There was a brief skirmish, but no further results. A symbolic new beginning had been made. As early as July 1940, Churchill "formed a command for amphibious operations"; on October 5, 1940, he instructed the planning staff to "investigate the possibilities of offensive operations in Europe, including the formation of a bridgehead on the Cherbourg peninsula."
By mid-September 1940, the Royal Air Force had achieved air superiority and had already shattered parts of the German transport fleet, so Hitler opted for a "postponement of 'Operation Sea Lion' for an indefinite period."
Events in the period 1940-1941
Toward the end of 1940, Hitler undertook an initiative to be able to continue the war against England offensively and proposed to the Soviet Union a "four-power pact" (still with Italy and Japan) for the "distribution of the British Empire" and the "delimitation of their spheres of interest in a worldwide framework." The discussion of this took place in Berlin on November 12 and 13, 1940, between Ribbentrop and Molotov and, at times, with Hitler. While the Germans were not playing with their cards on the table (the idea was "to pull Russia away from the Balkan sphere and orient it toward the East" - Hitler to Mussolini on November 20, 1940), Molotov had clearly defined Soviet interests - the Black Sea and the Baltic as well as the Balkans - and asked specifically about German intentions and demanded guarantees for the Soviet Union. Hitler kept a low profile in response, and when, two weeks after the conference, Stalin reaffirmed the aforementioned definition of Russian interests, "Hitler's reply [...] was not sent to Moscow, but went on December 18 [1940] as an instruction to his chief commanders: 'The German Wehrmacht must be prepared, even before the end of the war against England, to crush Soviet Russia in a rapid campaign' (Fall Barbarossa)." It still looked to Hitler as if he could put the British on the strategic defensive by conquering the Mediterranean, but this plan was put a decisive damper on by Franco's renunciation of the alliance on February 26, 1941.
On February 8, 1941, after the Senate, the House of Representatives also approved Roosevelt's Lend-Lease Act in support of Great Britain. This also made it clear to Hitler that he had to crush the Soviet Union as quickly as possible if he wanted to avoid a war on two fronts.
After the beginning of the German attack on the Soviet Union on June 22, 1941, Churchill expressed on the same day: "We have only one goal, one irrevocable task. We are determined to destroy Hitler and every vestige of the Nazi regime. Nothing will deter us from this - nothing." Soon after, Roosevelt reiterated this statement.
On October 3, 1941, Hitler had already announced his victory in the East and, by the end of September 1941, had already ordered the necessary rearmament to build up the air and naval power needed for the immediate attack on the British Isles. When the Red Army launched a counteroffensive outside Moscow on December 5, 1941, the illusion of a quick end to the campaign was shattered.
Tug of war for the second front
As late as June 1941, when "Russia was changing from an unfriendly neutral to an ally in need of help, Stalin sent Churchill the first of a series of letters urging the immediate formation of a second front in France." When Stalin's letter of September 4, 1941, became a reproachful demand, a sharp controversy arose with Churchill. Nevertheless, Churchill immediately directed the planning staff to complete planning for operations on the mainland, which it did in December 1941 as a draft with reference to the summer of 1943.
Two weeks after the attack on Pearl Harbor, the U.S. naval base in Hawaii, on December 7, 1941, and the consequent entry of the United States into the war, Churchill and Roosevelt and their command staffs met for the Arcadia Conference in WashingtonD.C. (December 22, 1941-January 14, 1942). "They decided to pool the entire military and economic resources of the two nations under the direction of a joint command, the 'Combined Committee of Chiefs of Staff.'" Dispelling British fears that the Americans would change their objectives after Pearl Harbor, General George C. Marshall, chairman of the committee, said, "Despite the entry of Japan into the war, it is still our view that Germany is the chief enemy and her defeat the key to victory. Once Germany is defeated, the collapse of Italy and the defeat of Japan must follow."
On March 9, 1942, Roosevelt again took the initiative, and on April 8, Marshall and Harry Hopkins, the president's personal adviser, arrived in London. Preparations for Operation Roundup, which called for a landing in northern France in 1943, were now followed by a decision on April 14, 1942, to plan Operation Sledgehammer as an "emergency measure" (Churchill) in case "a landing in France should be attempted in 1942 if a desperate enterprise should become necessary to save the Soviet Union from collapse."
To "make the most of the interval," Roosevelt accepted Churchill's proposal to carry out what was then called Operation Torch, an Anglo-American landing in Tunisia.
The "desperation" also stemmed from the fact that, in addition to the advance of Japan and the unclear situation in Africa, the naval war in particular began to develop disastrously for the Western Allies.
In May 1942, Molotov arrived in London "to negotiate an Anglo-Russian alliance and to learn our views on the opening of a Second Front." After Molotov had also been to Washington in the meantime, a communiqué was issued in London on June 11, 1942, which contained the sentence: "In the course of the negotiations full understanding was reached on the urgent task of establishing a Second Front in Europe in 1942."
Churchill writes further: "But to me it seemed above all important that this attempt to mislead the enemy should not also mislead our ally. I therefore handed Molotov [...] an aide-mémoire in which I made it clear that while we were trying our best to make plans, we were not committing ourselves to any action and could make no promise."
Throughout the summer of 1942, work was done on "Sledgehammer," but this only led to the realization of the hopelessness of the enterprise. The file was closed: "We were all in favor of the great Channel crossing in 1943, but inevitably the question arose: what do we do in the meantime? [...] President Roosevelt was determined that as many Americans as possible should face the Germans as early as 1942. Now where could this be achieved ? [...] in French North Africa."
Landing in Dieppe
The Allies also planned to carry out an attack on the French town of Dieppe, the main purpose of which was to explore whether it would be possible to hold a port on the occupied mainland for a short period of time. Furthermore, intelligence information was to be gathered and the behavior of the German occupiers was to be analyzed. This Operation Jubilee emanated largely from Admiral Lord Louis Mountbatten, Chief of Combined Operations, and took place on August 19, 1942. Most of the soldiers selected for the attack were Canadian, who were to take part in a combat mission again after a long time.
In Great Britain, the realization solidified that the second front in Western Europe demanded by Josef Stalin could not yet be built in 1942. Furthermore, the Dieppe attack provided important insights for the later Operation Overlord. The extent to which the mock attack was intended to convince Stalin that the invasion he had demanded was not yet possible in 1942 is disputed among historians.
Nazi propaganda tried to play up the failed Allied advance as a failed attempt at a large-scale invasion. Allied losses totaled 4304 killed, wounded and captured, including 907 dead Canadians. Of the 4963 Canadians, 2210 returned after the engagement, many of them wounded. In all, about 2000 Allied soldiers became German prisoners of war. 119 Allied aircraft were lost (including 106 aircraft, the highest one-day loss in RAF history). In contrast, the Wehrmacht suffered losses of about 591 men (at least 311 killed and 280 wounded), plus 48 aircraft.
The planning for 1944
At the Casablanca Conference in January 1943, after the first invasion of the North African coast, Operation Torch, which had meanwhile been successfully carried out, the Combined Chiefs of Staff concluded that preparations for Operation Roundup would not be completed before mid-August. This would make it impossible to launch the invasion until late fall 1943, which meant that Roundup could not support the Soviet summer offensive. The landing on the Italian coast in Sicily was to be brought forward, and the invasion of Western Europe was postponed until 1944, with the British still reserving the option for a small bridgehead beginning in late 1943. In addition, it was decided to destroy the German air force by air raids as late as 1943, followed by attacks on supply installations, in preparation for the big landing in 1944.
At the U.S.-British Trident Conference in Washington in May, Churchill and Roosevelt settled on May 1944 as the invasion date. Stalin was informed after this conference that there would be no more invasion in 1943. At the Quadrant Conference in Quebec in August, the first detailed plans for Operation Overlord were presented.
First plans as Operation Skyscraper
The Roundup plan was significantly expanded as of March 1943 by British Lt. Gen. Frederick E. Morgan, who later became COSSAC, significantly expanded. A first version, called Operation Skyscraper, provided for a landing on the beaches near Caen and the eastern Cotentin beaches, with four divisions forming the first wave and another six following it directly. In addition, eleven special task forces were planned for special operations and likewise four airborne divisions to attack German supplies. After the first bridgehead, which included Cherbourg, the capture of other ports to secure their own supplies was planned. The advance was to be toward the ports at the mouth of the Seine, with a necessary further landing at Le Havre. Further on, Antwerp was to fall in order to deploy Allied forces between the Pas-de-Calais and the Ruhr. Skyscraper's planning was dominated by the discovery of the main problems for a Channel crossing, which were essentially the provision of a sufficient number of landing ships. An absolute minimum was considered to be a number of ten divisions to be carried, which would be just sufficient to fight the current enemy units in the west. If the Allies failed to prevent additional German troop transfers to France, the invasion fleet would have to be increased to transport more divisions. Two additional divisions had to be ready for coastal defense.
Operation Skyscraper made great demands, not least to untangle the interdependencies of troop strengths, materiel availability, timelines, and costs that contributed significantly to the stalemate in Roundup planning. But planners also pressed for a quick decision so as not to have to enforce their demands against an emerging adversary buildup. The longer the planning phase dragged on, the more it became apparent that the Allies were not yet ready for an invasion. After all, the goals for Operation Skyscraper were too lofty. The British planners withdrew from the staff because the idea of "determined resistance" did not seem to them to be sufficient to determine the number of attacking divisions. Thus there was a break in the invasion planning.
Operation Overlord
Because some of the planners transferred to the COSSAC staff, many of the Skyscraper ideas were not lost and were carried over into Operation Overlord. However, General Morgan also saw that a fresh start with a new approach was inevitable. While a great deal of actionable data had been collected, a consistent, practical plan was still lacking. Morgan instructed his planning staff to take the existing plans into account as much as possible to save time, but to approach the planning effort as something entirely new.
The overall concept then presented consisted mainly of a large-scale land offensive, culminating in the invasion and occupation of Germany with some 100 divisions. The opening scenario was to be contested by a Canadian force in the southwest, while the main force in the United States stood ready to cross the Atlantic. Given the need for air support, the attack was to be made on the left flank, opposite British units. Additional American forces were to extend the beachhead and capture the ports through which the main U.S. units were to land. To avoid confusion of administrative responsibilities, it was better to refer to the Canadian beachhead as the Americans' left flank cover. In any case, the opening of the Atlantic ports meant moving the site of the invasion further west from the east. Thus, Morgan quickly realized that the landings could only take place in France. Conquering the ports in Belgium and the Netherlands would have meant that the landing forces would also have had to take up the fight for Germany directly.
Assuming that the Germans would establish the best possible defenses on the coast, and considering the resources available to the Allies, Commodore John Hughes-Hallett, the British naval chief planner, estimated in May that the landing force would have to consist of four divisions with an additional 16,000 troops in armored landing craft and about 12,000 vehicles in LSTs and similar vessels. Another division would have to go ashore within 24 hours.
But the main problem, the availability of landing ships of all kinds, was still not solved. The British tried to get an assurance from the Americans that the ships would be available in time. However, due to the then current situation in the Pacific War, the Americans could not be persuaded to give such an assurance for the time being, even though mass production of amphibious units had been in full swing since 1942 due to the Marshall Memorandum. The responsibility for this lay with the U.S. Navy, which built all kinds of ships from gunboats to aircraft carriers in its shipyards but had no experience whatsoever with landing craft. In addition, the shipyards were still heavily burdened with older orders. For this reason, they turned orders over to smaller shipyards in the American interior. However, it became difficult to find and train the crews that sailed the boats to the Atlantic coast. This task was eventually taken over by the U.S. Coast Guard with technically poorly trained personnel. For example, a serious accident almost caused by a young commander of an inland ferry was narrowly avoided. He was steering a landing craft down the Niagara River at night and missed the turn into the Erie Canal, heading straight for Niagara Falls. Disregarding all warning signs from shore, however, his boat ran aground a few hundred yards from the falls. When he was later questioned, he testified that he must have seen the light signs, but did not know their meaning. This inexperience delayed the program but could not seriously jeopardize it. In February 1943, the program ended as planned for the time being, with a record 106,146 displacement tons of ships built. The program continued thereafter, but production figures were brought down, and by May 1943 only 60,000 tons a month were being produced.
The British urged the U.S. to increase production in order to have the planned landing fleet by the scheduled date in the spring of 1944. Since the British production facilities themselves were operating at full capacity, the boats had to come from the United States. In return, the Americans argued that their other shipbuilding programs had been delayed by the high output of landing craft since 1942, and they were unwilling to accept any further delays in orders for the next six months.
Tehran Conference
At the Tehran Conference in November 1943, an anti-Hitler coalition conference attended for the first time by Josef Stalin, U.S. President Franklin D. Roosevelt and British Prime Minister Winston Churchill announced Operation Overlord to land in northern France in May 1944.
Operation Dragoon was under discussion for a second landing to take place in southern France.
Churchill wanted to postpone this second landing and first conquer northern Italy as well and then land in the Balkans to counterbalance the Soviet advance there. He did not succeed in doing so. While the British and Americans proposed two separate actions, Stalin wanted to see them as a simultaneous pincer attack from the south and north of France on the German occupiers. This put the Western Allies under pressure to act, and they began to work out Operation Overlord, as well as Operation Dragoon, in final detail now. As early as the beginning of 1944, they began the first exercises for the landing in Great Britain, which, however, could not yet follow the elaborations for Operation Neptune, the attack plan for the Normandy coast, since this existed only in its outlines at that time.
To this end, a joint command post was contemplated that would have to coordinate the preparation and execution of the operation. This was established with the creation of the Supreme Headquarters Allied Expeditionary Force (SHAEF) in mid-February 1944. SHAEF included, in addition to the command staff and operational divisions, a reconnaissance division that was extremely important for scouting German positions for the planned landing.
The SHAEF staff took the outline of the plan developed by Frederick E. Morgan and shaped it into the final version, Operation Overlord, launched on 6 June 1944 by General Dwight D. Eisenhower and the land forces commander for the initial part of the invasion, General Sir Bernard Montgomery.
The planning mainly included the following operations:
- Various training operations for the sea and land forces involved, for landing on the beach sections, including the Exercise Tiger
- Operation Fortitude to distract and disinform German intelligence and reconnaissance (see below Allied Deception Arrangements ("Operation Fortitude")).
- Operation Neptune - assault on the Normandy fortifications and the establishment of a beachhead including the construction of two supply ports (Mulberry Harbor).
- Conquest of Cherbourg with its deep water port
- Achievement of air supremacy over Normandy and later over the whole of France
- Conquest of the entire French Channel coast with its ports
- Advance of troops on Paris with the aim of liberating the city
- Liberation of all France
- Planning a strategic bombing of German targets on German soil
- Formation of an allied western front.
German measures
- Hitler's 'Instruction No. 51' (dated November 3, 1943; even before the Teheran Conference, the last strategic instruction he issues) provides for a reinforcement of German forces in the West to repel an Allied invasion. ('The danger in the East has remained, but a greater one in the West is looming; the Anglo-Saxon landing!' [...] If the enemy succeeds here in breaking into our defenses on a broad front, the consequences will be incalculable.'' [Hitler]).
- Mid-December 1943: Field Marshal Rommel begins reviewing defensive measures in France, Belgium and the Netherlands. On January 1, 1944, Rommel, as OB of H. Gr. B - under OB West (v. Rundstedt), takes over "the command of all German forces north of the Loire".
- May 1944: Formation of Army Group G. (Generaloberst Blaskowitz) in France south of the Loire under OB West.
- June 6, 1944: At breakfast, Hitler receives the news of the invasion of France. He remarks to Keitel: 'The news couldn't be better. As long as they were in England, we couldn't catch them. Now we finally have them where we can beat them.'
Preparation
Special equipment of the Allies
Early in 1944, Major-General Percy Hobart, Eisenhower, and Montgomery were able to demonstrate a brigade of buoyant DD tanks, Crab minesweepers, and AVRE tanks, as well as a regiment of "Crocodile" flamethrower tanks, all of which belonged to Hobart's Funnies. Montgomery was convinced that they should also be made available to U.S. forces and offered them half of the available vehicles. The Americans reacted cautiously to this proposal. Eisenhower liked the floating tanks, but he left the decision to other leaders, such as General Omar Bradley, who in turn referred them to his officers. The Americans did not accept any of the other designs.
Recognizing the need for some new experimental vehicles to aid progress on the French invasion beaches, Field Marshal Alan Brooke's decision to develop them had already been made in 1943. It was necessary to clear the obstacles on the British landing beaches as quickly as possible, since the relatively flat hinterland made an early German counterattack possible. Some of the ideas were somewhat older, tested, and had already been used, such as the Scorpion "flail" tanks, converted Matilda tanks that had cleared the way for the British through the German minefields in North Africa.
The invasion plan also called for the construction of two artificial Mulberry harbors to bring troops and equipment ashore during the first weeks of the invasion. Furthermore, pipelines were to be laid under the water to supply the Allied forces with fuel (Operation PLUTO).
Reconnaissance Operations
Using aerial photographs, drawings by the Resistance, the collection of private vacation photographs in Great Britain, and individual commando operations in which complementary sand and rock samples were taken, the Allies created a profile of the landing area.
The British Admiralty addressed the public via the BBC on May 19, 1942, with a request that postcards and photographs showing the French coast be sent to them. Within a short time, the Admiralty received nine million photographs and maps, of which about 500,000 were copied and analyzed by experts. In this way, a multitude of geological details were discovered that had not been recorded on any map.
In the fall of 1943, the Allied cartographers then realized that the maps of Normandy were based on surveys from 1895/96 and were therefore of limited use. Therefore, all landing sections were photographed from an altitude of 10,000 meters as well as in low-level flight. As a diversion, for each flight over Normandy, two were made in the Pas de Calais. The goal was to produce a "D-Day Invasion Map" to help all units find their way. The map series was completed in June 1944 and went into production with a total print run of over 18 million copies.
On the night of July 3 to 4, 1943, ten members of the so-called "Forfar Force," a special unit consisting of the X "German" Troop of the 10th Inter-Allied Command and the Special Boat Section (SBS), landed near the Norman seaside resort of Onival near Le Tréport. The landing was the first of seven reconnaissance raids during the course of Operation Forfar Easy, the purpose of which was to identify German formations stationed near the coast, determine the extent and nature of beach obstacles, record German positions, and take ground samples. Equipped with German uniforms and weapons were the German-speaking soldiers of the task force. In some cases, the squads stayed for long periods in villages in the Pas-de-Calais area and Normandy, trading postcards with marked German positions for chocolate with the locals. By August 1943, the task force had completed its operation.
During preparations for the Normandy landings, British chariots (manned torpedoes) and combat divers were also used to search the seabed along the Normandy coast for obstacles. These examined the waters and inspected the beach as far as was possible, therefore providing the Allies with good information on the landing area. Furthermore, models of the area were built based on Royal Air Force (R.A.F.) aerial photographs and reports from French resistance fighters.
On January 12, 1944, the Combined Operations Pilotage Parties (COPP) noted that there might be some problems with the landing beaches because peat and clay were found in samples. Physicist J. D. Bernal described possible effects of the peat and clay:
"A large part of the area between Asnelles and la Rivière will prove impassable even to lightly equipped infantry without vehicles."
"Much of the area between Asnelles and la Rivière (both communes in the canton of Ryes) will prove impenetrable, even to only lightly equipped infantry without vehicles."
Based on this report, further reconnaissance missions were ordered to take additional samples. French geologists were also sent to Paris to search for geological maps of Normandy. Four maps were found and smuggled to England, where they were examined by the Inter-Services Topographical Department at Oxford. Bernal's warnings proved too pessimistic, although the loss of some armored vehicles was to be expected.
On January 17, an Allied submarine, HMS X20, set sail from England during Operation Postage Able to scout the French coast for four days. During the day, the crew analyzed the shoreline and beach with a periscope and sounded the seabed with an echo sounder. During the nights, two of the crew members swam to the beach - each with special equipment that included an underwater notebook with pencil, a compass, a .45 revolver, and an auger. Soil samples were collected in preservatives. The divers went ashore on two nights to survey the beaches at Vierville, St. Laurent, Les Moulins, and Colleville, which would form the U.S. Omaha Beach section. On the third night they were to go ashore at the mouth of the River Orne, but were unable to do so due to exhaustion and poor weather conditions, whereupon they returned to England on January 21. They brought back information about the geology of the beaches, the position of rocks and the tides.
By March 31, the entire coast of northern France was already under observation by specially equipped Allied aircraft with horizontal and vertical cameras. Reconnaissance flights revealed that the number of German batteries had increased from 16 to 49 artillery batteries (for the entire coast of northern France) within eight weeks.
Exercises and planning gaps
The Allies rehearsed the invasion months before D-Day. For example, on April 28, 1944, Allied forces practiced a landing south of Devon during Exercise Tiger. When the convoy of ships was discovered and torpedoed by German speedboats, 749 U.S. soldiers lost their lives.
A threat to the success of Operation Fortitude (see Allied Deception Arrangements ("Operation Fortitude")) and thus to the entire invasion was the prohibition on travel to and from the Republic of Ireland (which was neutral and partially cooperating with the Germans), as well as the prohibition on movement in the coastal areas used for Operation Overlord. To invalidate this clear indication of invasion, Allied intelligence agencies showered the German consulates with misinformation, so the prohibitions were ultimately ignored by the Germans.
In the weeks leading up to the invasion, the surprisingly large number of crosswords in the British Daily Telegraph, which were also code names in the invasion, caused an uproar among the planners of Operation Overlord. British intelligence MI 5 at first thought this was a coincidence, but when the word "Mulberry" appeared, they became uneasy and sought out the creator of the puzzle. The creator, a teacher, knew nothing about the operation; however, it later turned out that the words had been suggested by his students, who had heard them from soldiers but did not know what they meant.
There were several gaps in planning before and on D-Day. One significant Allied error revolved around General de Gaulle's radio message after D-Day. He stated there, unlike all other Allied leaders, that the Normandy invasion was the correct and only invasion. This statement could affect the overall impact of Operations Fortitude North and South. Eisenhower, for example, referred to the invasion as only an initial invasion. The Germans, however, did not believe de Gaulle; they persisted in expecting a second invasion at a different location and therefore did not move additional units into Normandy.
Operation Anvil/Dragoon
The Allies planned Operation Anvil (= anvil) in addition to Operation Overlord, which was then called Operation Hammer. Winston Churchill feared that Anvil would spread the fighting power of the Allied forces over too many theaters of war at the same time and cause the Western Allies' formations to advance toward Berlin more slowly than the Soviet allies. He later claimed to have been badgered until he accepted the invasion, which was then to take place under the code name Operation Dragoon.
American proponents expected the operation to result in the rapid capture of two major ports-Toulon and Marseilles-whose capture would greatly facilitate the supply of troops fighting in France, including those fighting in Normandy. In fact, by the time Antwerp was captured in December 1944, about one-third of the total Allied troop supply could be transported from Marseilles to northern France via the Rhône route, including repaired bridges and rail lines. Operation Dragoon was to begin on the Côte d'Azur between Toulon and Cannes on August 15, 1944.