D-Day Development of Overlord ... Part 3

In the initial phases of OVERLORD, Field Marshal Montgomery, whom I had designated as tactical commander of the early land battles, was to have operational control of all land forces, including the United States First Army until the growing build-up of the American forces made desirable the establishment of an independent Army Group. When sufficient forces had disembarked on the Continent, a United States Army Group was to come into being, equal both operationally and administratively to the British 21 Army Group, which latter was to continue under Field Marshal Montgomery's command. Although no definite time was set for this, it was estimated that it would take place when the Third Army had become fully operational; the date was also dependent, of course, upon the progress of the initial land battles beyond the beachhead area where, as already pointed out, simplicity of command in a narrow space was desirable.

In the matter of command, it can be said here that all relationships between American and British forces were smooth and effective. Because of certain fundamental national differences in methods of military supply and administration, it was early agreed that no unit lower than a corps of one nationality would be placed under command of the other nationality except where unavoidable military necessity made this imperative.

To carry out the mission of invading Western Europe, there were to be available, by D-day, in the United Kingdom 37 divisions: 23 infantry, 10 armored, and 4 airborne. These were to be employed in the assault and subsequent build-up period in France.

[The US Divisions that were actually employed in this operation were the 1st, 2nd, 4th, 8th, 9th, 29th, 30th, 35th, 79th, 90th Infantry Divisions; the 2nd, 3rd, 4th, and 6th Armored Divisions; and the 82nd, and 101st Airborne Divisions.]

As the campaign progressed, the flow of divisions to the Continent was to be maintained at a rate of three to five divisions per month, and this flow was to be augmented by the divisions entering the European Theater with the assault against Southern France from the Mediterranean. [These were the 3rd, 36th and 45th US Infantry Divisions.] Ultimately, at the time of the German surrender, I had under command a total of go divisions: 61 American, 13 British, 5 Canadian, 10 French, and 1 Polish. These divisions, with antiaircraft, antitank, and tallk units habitually attached, averaged about 17,000 in combat strength, well over twice the strength of Russian divisions. In addition there were three French divisions which were not completely equipped, and lesser units of Czech, Belgian, and Dutch forces on the Continent, as well as the units of the French Forces of the Interior. Our Headquarters estimated that, at times, the value of these latter French forces to the campaign amounted in manpower to the equivalent of 15 divisions, and their great assistance in facilitating the rapidity of our advance across France bore this out.

The initial success of the land forces in the assault against Northwest Europe was dependent upon the operations of the Allied Naval Expeditionary Force under the command of Admiral Ramsay. In his operational orders issued on 10 April, he clearly defined the Navy's mission to those under his command: "The object of the Naval Commander-in-Chief is the safe and timely arrival of the assault forces at their beaches, the cover of their landings, and subsequently the support and maintenance and the rapid build-up of our forces ashore." To accomplish this mission successfully months of de· tailed planning and training, closely coordinated with the ground and air forces, were necessary.

Reports on the North African and Sicilian Campaigns have made mention of the magnitude of the naval forces involved, but the sea power displayed there was to fade by comparison with the forces to be employed in this great amphibious assault. The extent of the problem of berthing, loading, and moving the forces involved may be realized Witll the knowledge that over 5,000 ships and 4,000 additional "ship-to-shore" craft were to be engaged in the Channel operations during the assault and build-up period. That everything went according to plan is a remarkable tribute to the hard work, coordi· nated effort, and foresight of the thousands engaged in the initial planning and train ing, and, as Admiral Ramsay stated in his report, to the "courage of the tens of thousands in tl,e Allied navies and merchant Beets who carried out tl,eir orders in accordance with the very highest traditions of the sea."

With the expansion of the assault from a three-divisional to a five-divisional attacking force, increased naval forces were necessary both to protect the invasion Fleet en route and to bring added fire power to bear on the beaches. These were allotted by the Combined Chiefs of Staff on 15 April 1944. The chief units in the final naval forces included 6 battleships, 2 monitors, 22 cruisers, and 93 destroyers.

Under the naval plan the assault area for the naval forces was bounded on the north by the parallel of 49° 40' N, and on the west, south, and east by the shores of the Bay of the Seine. This area was subdivided into two Task Force Areas, American and British, the boundary between them running from the root of the Port-enBessin western breakwater in an 0250 direction to the meridian of 0°4°' W, and thence northward along this meridian to latitude 49°40' N. Within these defined areas, the Western Task Force, operating in the American zone, was under the command of Rear Adm. A. G. Kirk, and the Eastern Task Force, operating in the British zone, under the command of Rear Adm. Sir P. L Viano The Western and Eastern Task Forces were again subdivided to include, altogether, five assault forces, each responsible for the landing of an assault division upon one of the five beach areas, and two follow-up forces. The assault forces were known for the American zone as Force "U" and Force "0" (Utah and Omaha) and were under the command respectively of Rear Adm. D. P. Moon and Vice Adm. (then Rear Adm.) J. L. Hall, Jr. For the British zone the assault forces were similarly known as Force "S", Force "J", and Force "Gil (Sword, Juno, and Gold) and were commanded by Rear Adm. A. G. Talbot, Commodore G. N. Oliver, and Rear Adm. C. Douglas-Pennant.

In order to insure the safe arrival of the assault troops on the beaches, the Navy was to provide adequate covering forces to protect the flanks of the routes of our assault and was, with mine sweeping vessels, to clear the Channel ahead of the assault craft. For this latter purpose I 2 mine sweeping flotillas were to be employed. Once within range of the beachhead area, the heavy naval guns were to neutralize the enemy coastal batteries, supplementing the work of the Air Forces, and then, as the landing craft drove inshore, there was to be an intense bombardment of the beach defenses by every gun that could be brought to bear.

Some consideration had initially been given to the possibility of assaulting at night in order to obtain the maximum surprise, but it was decided that the lessons of the Pacific should be ad hered to, and that, possessing superiority in air and naval forces, the assault against strong defenses should take place by day. This was palpably advantageous to the Navy in the coordinated movement of a vast fleet in relatively narrow waters. H-hour varied for most of the five assault forces, due to varying beach conditions such as the necessity for higher tide to cover certain rock obstacles and the length of time needed to remove enemy obstructions. Force "U" was to touch down at 0630 hours while Force "J" was not to land until 35 minutes later.

With the success of the assault determined, the naval forces were to maintain swept channels between France and England th rough which supplies and reinforcements could be shuttled to the Continent. In view of the initial limi ted port facilities and the fact that we did not anticipate seizing the Brittany ports for some time after the assault, the Navy was also charged with providing for the establishment off the French coast of five artificial anchorages (Gooseberries). Two of these were subsequently to be expanded into major artificial harbors (Mulberries); through these the bulk of our stores were to be unloaded during the early stages of the campaign. To provide oil and gasoline in bulk, the Navy was also to set up tanker discharge points off the French coast and to establish cross-Channel submarine pipe lines.

By 26 April, the five naval assault forces were assembled in the following areas: Force "U," Plymouth; Force "0," Portland; Force "S," Portsmouth; Force "G," Southampton; and Force "J," Isle of Wight. The two follow-up forces, Force "B" and Force "L," were assembled in the Falmouth-Plymouth and Nore areas. in addition to the berthing problems inherent in the assembly of these seven forces, other space had to be found for the many ships and craft which were assigned the tasks of supply, maintenance, repair, and reinforcement. The berthing problem was one of major proportions, but it was solved, as Admiral Ramsay reported, by making use of every available berth from Milford Haven to Harwich. Many units had, additionally, to be berthed in the Humber, at Belfast, and in the Clyde.

The concentration of ships in southern ports was bound, we felt, to be detected by the enemy and would thus give him some indication that our assault was about to be launched. In order to confuse him in this respect, arrangements were made with the British Admiralty to have the large number of commercial ships destined for the Thames and also the ships to be used in later supply convoys to our forces on the Continent held in Scottish ports until the operation was under way. The concentration of shipping thus spread itself automatically throughout the whole British Isles and was not confined to a single area. As was the case against Sicily, we did not believe that the growing preparations and the size of our forces could be entirely concealed from the enemy. We hoped, though, to be able to confuse him as to the time of the assault and the exact beachhead area of attack. In this we were to be successful for a variety of reasons which I shall consider later.

The air plan in support of the amphibious operation consisted of two parts, the preparatory phase and the assault phase, and was brought into being under the direction of Air Chief Marshal Leigh-Mallory, commanding the Tactical Air Forces. These forces, composed of the British Second Tactical Air Force and the U. S. Ninth Air Force, were to operate in direct support of the land armies. The Strategic Air Forces also would be given definite tactical responsibilities during critical periods, although their principal mission would be to continue their attacks on the industrial potential of Germany, with emphasis now placed on the facilities for aircraft production. They had also definite tactical responsibilities at critical periods of the battles.

Until January 1944, the view had been held that the heavy bombers of the Strategic Air Forces could make sufficient direct contribution to the assault in a period of about a fortnight before D-day. Further consideration, however, indicated the need to employ them for a much longer period-about three months-and a plan was finally adopted which aimed at the crippling of the French and Belgian railway systems and the consequent restriction of the enemy's mobility. The plan had a wider conception than the dislocation of the enemy's lines of communication in the zone in which the land forces were to be deployed. It was looked upon as the fust of a series of attacks, which as they spread eastward, would ultimately affect the whole German war effort. The adoption of this plan entailed a major effort by the Strategic Air Forces.

In the preparatory phase, the striking power of the Tactical Air Forces was to be directed against rail targets, bridges, airfields in the vicinity of the assault area, coastal batteries, radar stations, and other naval and military targets. In addition to reserve aircraft, these forces had operationally available 2,434 fighters and fighter-bombers, and 700 light and medium bombers.

The program of attack on rail centers and bridges was designed to deprive the enemy of the means for the rapid concentration of men and material and to hinder his efforts to maintain an adequate Row of reinforcements and supplies, forcing him to move by road with resultant delay, increased wastage in road transport and fuel, and increased vulnerability to air attack. Blows against the railroad centers were to be started about Dminus- 60 and were to cover a wide area so as to give the enemy no clue to our proposed assault beaches. Shortly before D-day, however, the attacks would be intensified and focused on key points more directly related to the assault area hut still so controlled as not to indicate to the enemy the area itself.

Attacks against coastal batteries, airfields, bridges, and other targets in the preparatory period were planned in such a manner that only one-third of the effort expended would be devoted to the targets threatening the success of our assault. The preliminary attacks upon the bridges in Northwestern France were scheduled to begin on D-minus-46 and to be intensified in tempo as D-day approached. The ultimate purpose of these at-tacks was to isolate the battle area from the rest of France by cutting the bridges over the Seine and the Loire below Paris and Orleans, respectively. The attacks upon the airfields had a similar purpose. Within a 130-mile radius of the battle area, all enemy airfields and air installations were to be attacked beginning not later than D-minus-21. By neutralizing the fields, we were certain to limit the maneuverability of German fighter forces, compelling them to enter the battle from fields situated a considerable distance from the Normandy beaches.

This preparatory bombing program was placed in effect as scheduled and, as D-day approached, the intensity of our attacks increased and the preparatory phase gave way to the assault phase. In the assault itself, the air forces were assigned the tasks, in conjunction with the navies, of protecting the cross-Channel movement of our forces from enemy air and naval attack. They were also to prepare the way for the assault by destroying the enemy's radar installations and by neutralizing coastal batteries and beach defenses between Ouistreham and Varreville, the area of our attack. Additionally, the air forces were to provide protective cover over the landing beaches and, by attacking the enemy, reduce his ability to reinforce and counterattack. Sub.sequent to the establishment of the beachhead, the Tactical Air Forces were to support the land troops in their advance inland from the assault beaches.

During the assault it was planned to maintain a sustained density of ten fighter squadrons to cover the beach area, five over the British sector and five over the American. An additional six squadrons were to be maintained in readiness to support the beach cover if necessary. Over the main naval approach channels we agreed upon a sustained density of five squadrons centered at 60 miles and three at 80 miles from the South coast of England. Additionally, a striking force of 33 fighter squadrons was to be held in reserve for use as the air situation might require, subsequent to its initial employment as escort to the airborne formations.

The total fighter aircraft which we allocated for the D-day assault was as follows: Beach Cover (54 Squadrons), Shipping Cover (15 Squadrons), Direct Air Support (36 Squadrons), Offensive Fighter Operations and Bomber Escort (33 Squadrons), Striking Force (33 Squdrons), for a Total of 171 Squadrons.

The photographic reconnaissance units of the Allied Air Forces were the first to begin active and direct preparations for the invasion of Europe from the west. For more than a year, much vital information was accumulated which contributed very greatly to the ultimate success of the assault. The variety, complexity, and the detailed accuracy of the information gathered was of great importance in the preparatory phase of the operation. One of the most remarkable tasks accomplished by these reconnaissance units was the series of sorties flown to obtain low-level obliques of underwater beach defenses.

Battle of the Bulge | D Day