Preparing for Continental Invasion
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Chapter 4: The Inception of OVERLORD and its Logistic Aspects
Early Planning for Cross-Channel Operations
The plan by which Allied forces successfully launched a cross-Channel invasion and captured a lodgment on the European Continent eventually bore the name OVERLORD.1 Planning for a return to the Continent was begun by the British shortly after their withdrawal from France in 1940. But the scope of such planning as could be undertaken in the next year or two was severely restricted by the meager resources available, and could hardly go beyond such limited-objective schemes as large-scale raids aimed at aiding the USSR by diverting enemy forces from eastern Europe, or plans for a rapid movement to the Continent to take advantage of the enemy’s collapse. Plans for a return to the Continent in force had little practicality until the United States entered the war, and even then were long in coming to fruition.
The first major impetus to cross-Channel planning after U.S. entry into the war came with the approval of the Marshall Memorandum in London in April 1942.2 Commanders of the ground, air, and naval services of both the British and U.S. forces in the United Kingdom started holding formal conferences on invasion plans the following month and set up both operational and administrative planning staffs to begin the study of tactical and logistic problems involved in a cross-Channel operation. As already indicated, the plan for a full-scale cross-Channel invasion was at first referred to as ROUNDUP, the name which the British had already used to designate earlier plans for a continental operation. As envisaged in 1942, ROUNDUP called for landings on a wide front between Boulogne and Le Havre in the following spring.
ROUNDUP planning had hardly been initiated when the decision was made to invade North Africa, and as the preparations for the North African landings progressed that summer it became obvious that offensive operations in northwest Europe in 1942 were out of the question, since all available forces and equipment were committed to TORCH. In fact, the ROUNDUP planners foresaw little possibility of a major operation against the Continent even in 1943, and outlined their proposed planning with only limited objectives
in mind for that year—raids to provoke air battles, capture of a lodgment or a beachhead preliminary to possible exploiting operations (in the Cotentin, for example), and a return to the Continent to take advantage of German disintegration. It was important, nevertheless, that planning continue for large-scale operations against the Continent in 1944.
For this purpose the ROUNDUP plan continued to be used as a basis for administrative planning, since it was realized that the logistic preparations for such an operation would be tremendous, and would have to be developed far in advance of the detailed operational planning.3 The ROUNDUP planning staffs were to a large extent sponsored and guided by the British, although their numerous subcommittees contained both American and British representatives. They had no permanently assigned staff with the exception of a secretariat. The various committees met as the need arose and published their plans and proceedings in a series of reports. On the national level, planning in ETOUSA headquarters was initially the responsibility of the G-3. The special staff sections of theater headquarters in London at first did nearly all of the logistical planning for invasion. The SOS was little concerned with this planning in 1942, for it was not originally assigned such responsibilities by higher headquarters. Moreover, it lacked a strong agency on the general staff level to guide over-all planning, and its planning activities were limited by the preoccupation with current service of supply operations in the United Kingdom, and by a shortage of planning personnel. Among the unfortunate circumstances was the persistent lack of an official troop forecast, always considered essential to proper planning.4 Nevertheless, the ROUNDUP staffs continued planning for operations in northwest Europe throughout the fall and winter of 1942, although mainly with limited objectives in mind. They accomplished a great amount of spadework and assembled invaluable information relating to a cross-Channel attack.
At the Casablanca Conference in January 1943 the Combined Chiefs of Staff were occupied in the European area primarily with operations in the Mediterranean in 1943.5 Because of the demands of TORCH, plans for an all-out cross-Channel operation remained outside the scope of practicality for 1943. Allied fortunes had taken a decided turn for the better, however, and the Combined Chiefs at that time made a decision which proved tremendously reassuring to the future prospects for cross-Channel invasion. They agreed that a combined staff of British and American officers should be organized, preferably under a Supreme Commander, but if such an appointment was not immediately feasible, under a chief of staff, in order to give the necessary impetus and cohesion to planning for future operations. The mission of this staff was to include planning for “an invasion in force in 1944.”6
The reference to planning for large-scale operations on the Continent in 1944 occupied little space in the minutes of the Casablanca meetings. But the decision to
create a planning organization was implemented within the next few months. Late in April 1943 the British Chiefs of Staff issued the directive establishing the combined staff under General Morgan with the title Chief of Staff to the Supreme Allied Commander (Designate). An American, Brig. Gen. Ray W. Barker, was appointed as his deputy. The staff which General Morgan gathered around him came to be known as COSSAC, from the abbreviation of his title.
The acceleration of planning which now took place at the Allied level was also reflected on the national level. The SOS established a planning echelon in London to maintain close contact with higher headquarters, and the chiefs of the principal technical services thenceforth divided their time between London and Cheltenham. Planning was at this time transferred from the G-3 Section, ETOUSA, to a newly organized G-5 Plans Section, headed by General Barker. This new general staff section was charged with the coordination of all U.S. planning, both operational and administrative. Its main preoccupation, however, was planning at the Allied level, and the G-5 Section was for all practical purposes the U.S. component of COSSAC.7
COSSAC was assigned several missions. It was to evolve deception plans to keep alive the expectation that an attack was imminent in 1943 and thus pin down German forces in the west; it was to plan for a return to the Continent in the event of German disintegration. But its principal mission proved to be the creation of a plan for “a full scale assault against the Continent in 1944.”8
First of all, the COSSAC planners had to determine precisely what resources the Allies would have available in the United Kingdom for operations against the Continent. To get such figures the COSSAC staff presented estimates of the needs for an invasion at the Washington (TRIDENT) Conference in May. The proper size of the assault force was a much-discussed subject and one on which no final conclusions could be reached at that time. Allied resources at the moment, and even the resources estimated to be available at a later date, were appallingly meager for the type of operation envisaged. The Combined Chiefs of Staff nevertheless gave tentative approval to the idea of an invasion in northwest France in 1944 and provided the planners with the first estimates to work with in formulating a more detailed plan. Uncertainty as to the availability of landing craft was already casting its shadow over all operational planning.9
Late in June a five-day conference (known as RATTLE) was held in Scotland to consider the many problems of cross-Channel invasion. It was presided over by Vice Admiral Lord Louis Mountbatten, Chief of Combined Operations (British), and attended by COSSAC members and the commanders of the principal Allied forces in the United Kingdom. Detailed discussions were held on such subjects as suitable assault areas, weapons, tactics, and enemy defenses. General Morgan had already drawn up an outline plan for cross-Channel invasion and presented it to the 21 Army Group commander, the Air Officer Commanding-in-Chief (Designate) of the Allied Expeditionary Air Force, the Naval C-in-C (Designate), and the Commanding General, ETOUSA, for
their consideration.10 In July COSSAC prepared a digest of its plan, which received the approval of the British Chiefs of Staff. In the following month it was presented to President Roosevelt and Prime Minister Churchill and the Combined Chiefs of Staff at the Quebec (QUADRANT) Conference. There the OVERLORD plan was definitely accepted as the principal U.S.-British effort against Germany in 1944. In some respects the outline plan or digest presented at Quebec was more properly a staff study and was so regarded by the planners. Not until after the Cairo (SEXTANT) Conference in November-December 1943 did General Morgan feel confident enough about the future of the operation to emphasize to his staff that there was now at last a firm determination that the operation would take place at the agreed date. OVERLORD and ANVIL (the supporting operation to be launched in southern France) were to be the supreme operations for 1944. “Nothing,” it was emphasized, “must be undertaken in any other part of the world which hazards the success of these two operations....”11 While the detailed planning still remained to be done, and while there still were many unanswered questions, particularly regarding the scale of the assault and the availability of the means, the plan that COSSAC presented at Quebec in August 1943, refined and amended in the next nine months, was the plan finally executed as Operation OVERLORD in June 1944.
Logistic Considerations in the Evolution of the OVERLORD Plan
The continental operations of 1944–45 have frequently been referred to as a battle of logistics—a contest between the industrial capacities of the Allies and the war-organized economy of Nazi-dominated Europe. The purpose of the cross-Channel operation itself suggested the vital role which logistics was to have in the course of the battle: the object Of OVERLORD, in the words of the plan itself, was to “secure a lodgment on the Continent from which further offensive operations can be developed.”
The objective of the OVERLORD operation was not to bring about the defeat of the enemy in northwest Europe, but to seize and develop an administrative base from which future offensive operations could be launched. The OVERLORD plan did not even contemplate a decisive battle west of the Seine. Its objective was a limited one, therefore, determined by the essential logistic consideration that the Allies would require an administrative base with all the facilities, such as ports, depots, and transportation, necessary for the build-up and support of forces on the scale required for subsequent offensive operations.
For U.S. forces the preparation for such an operation entailed, first, transferring a huge force and its equipment to the British Isles across a submarine-infested sea route, and, second, funneling this force, against determined enemy opposition, into a narrow beachhead on the Continent, and adequately maintaining it. By the summer of 1943 the first of these tasks was finally well under way.
Once the decision was firm that an all-out invasion of the Continent should be made, two problems of overriding importance faced the planners: (1) determining the scale of the initial assult; (2) providing
an adequate build-up and maintenance. That these fundamental logistic considerations weighed heavily is evidenced in the earliest discussions. The second problem—that of an adequate build-up and maintenance—soon resolved itself into the problem of choosing an assault area. The ROUNDUP planners had emphasized from the start that the first phase of operations would be devoted to securing a lodgment area, the essential feature of which had to be sufficient discharge capacity—that is, facilities for the reception of personnel, vehicles, and supplies. The primary need, therefore, was port facilities. Indeed, one of the first estimates and drafts of the OVERLORD plan prepared by the Principal Staff Officers of COSSAC in June 1943 gave as the mission of the operation the securing of a lodgment on the northwest coast of France “in order to gain sufficient deep-water ports to accommodate the landing of large forces from the U.S.”12 This estimate was strengthened by the conviction that German defense policy was based on holding the coast line and, above all, the major ports, at all costs. The enemy appreciated that, if all major ports could be denied to the Allies, the already difficult task of building up and maintaining forces able to defeat armies backed by an excellent road and rail system would become impossible.13 In any assault on the Continent it was essential that the Allied rate of build-up should match or exceed the rate at which the enemy could bring up reserves,
Selection of an assault area had been the main planning consideration all through the winter of 1942–43, and port capacities were almost invariably the starting point for the discussion of any area. For purposes of study the planners normally divided the coast of northwest Europe into “port group” areas. The designation and boundaries of these groups varied somewhat, but in general there were five: the Belgian group (Dunkerque–Antwerp), the Pas de Calais group (Boulogne–Calais), the North Seine (Dieppe–Le Havre–Rouen), the Cherbourg or Norman (Caen–Granville), and the Brittany group (St. Malo–Nantes). (Map 4)
The ROUNDUP plans of 1942 were generally based on an assault on a wide front, extending roughly from Calais to Le Havre, with an additional landing west of the Seine, and the possibility of an assault on the Cotentin Peninsula. Late in the year there was a noticeable shifting away from these plans for multiple assaults toward the idea of a more concentrated attack on a narrower front.14 It was argued that if the assault was made in two or more widely separated areas simultaneously or on a particularly wide front, German reserves would be in action even more quickly. A larger number of routes would be available to them and there would probably be some reserves close behind each assault area. A faster Allied rate of build-up would be required. An assault on a narrower front was therefore preferable. Reinforcing this conclusion at the time was the belief that, even if unlimited landing craft were available, the capacity of ports and loading points on the south coast of England would restrict the size of the force which could be embarked and sailed on any one day.
Map 4: Ports Considered in Invasion Planning
An examination of the discharge capacities of each port group revealed that no group or combination of groups could maintain large forces when ports were first opened, and that a large number of ports would be required after thirty days’ development, even if they could all be captured simultaneously. After three months, however, it was estimated that any two adjacent groups would meet the needs of a large force, and that the Brittany group alone might suffice for a smaller force.
Assuming that the operation was to be carried out by a large force, the planners concluded that two groups of ports were required. The Normandy (or Cherbourg) and North Seine groups together possessed the maximum capacity in the least number of ports. The Normandy and Brittany groups together had a larger total capacity, but were considered to be less economical to develop. The other two groups—the Pas de Calais and Belgian—figured less favorably in the considerations primarily
because they constituted the very pivot of the enemy defense system. It followed therefore that of the possible combinations the Normandy–North Seine and the Normandy–Brittany groups were preferred. Since the Normandy group was common to both these combinations it was evident that if the Allies captured that area they could later choose between attacking either of the others. These considerations constituted a powerful argument for the choice of the Normandy coast for the assault.
An important additional determinant in the selection of an assault area was the need for suitable beaches. The Combined Commanders’ studies had shown that the required forces could not be maintained entirely through ports until approximately D plus 90 and that some maintenance would have to be carried out over the beaches throughout the first three months, supplemented when possible by air supply. The selection of the main assault area therefore depended as much on the characteristics of the beaches as on proximity to a group of ports. This would be the case, it was felt, even if the landings were unopposed, for the enemy was certain to demolish the ports before withdrawing.
Several factors had to be kept in mind in the search for suitable beaches. Of paramount importance was their capacity to accept and pass vehicles inland, for it would be necessary to put the force ashore at a rapid rate. To meet this prerequisite they had to be sheltered from prevailing winds and have sufficient width. Of varying importance were such features as the gradient, the tide range, the beach exits, and the terrain overlooking them. With these requirements in mind the planners concluded that the most favorable beaches lay in the Caen sector of the Normandy area. There the beaches were of large capacity and sheltered against westerly and southwesterly winds, permitting a large force to be put ashore rapidly and maintained over them.
The possession of beaches did not eliminate the necessity of opening a port quickly. No fully equipped force could achieve real mobility for more than a limited period while maintained solely over beaches. Furthermore, the bulk of the vehicles and stores would require a quayside for discharge if landing craft were limited in number and the larger Liberty ships had to be used. Consequently it was felt to be imperative that one major port be captured quickly. The only port of any importance in the Normandy area was Cherbourg, and to facilitate its capture the planners recommended that an assault in the Caen area should be extended to the eastern beaches of the Cotentin peninsula. A decision would later be necessary on whether to take the Seine or the Brittany ports.
These were by no means the exclusive considerations in the selection of an assault area. The enemy’s beach and coastal defenses, his probable rate of reinforcement, the feasibility of providing fighter cover in the assault area and of opening airfields in the beachhead, inland terrain and communications, and the naval problem—all figured in the study of possible landing areas. But the problems of logistic support occupied a preeminent place in every discussion.
The logistic problems of a cross-Channel invasion held continuing prominence in the 1943 planning. While considering the possibilities of carrying out a limited bridgehead operation against the Cotentin in 1943, or the chance of exploiting such an operation, the British Joint Planning
Staff emphasized at the Casablanca Conference in January that success hinged largely on the possibility of augmenting the limited port capacity of Cherbourg by the capture of additional facilities so that adequate forces and supply reserves could be built up. Even if German opposition was negligible, it noted, progress would be slow owing to the Allies’ limited resources in vehicle-carrying craft suitable for landing over beaches.15
The problem of continental discharge was again underscored after COSSAC took over the study of invasion problems in April 1943. In a memorandum to the British Chiefs of Staff General Morgan reiterated the argument that, in any amphibious operation against opposition, the rate at which Allied forces could be built up after the initial assault must play a decisive part in the outcome. In the special case of a cross-Channel operation this would depend mainly on the volume of supplies and equipment, especially vehicles, that could be landed from LSTs and LCTs.16 Full use of these specialized ships and craft could be made only if adequate facilities existed for unloading them on the French coast. General Morgan was not satisfied that the berthing facilities on the far shore were adequate, observing that if the beaching of landing craft was relied on until ports were captured and put into use the turn-round period would be considerably longer than necessary, and ships would be unnecessarily exposed to attack. Furthermore, the whole operation would be excessively dependent on favorable weather. In June General Morgan asked his administrative planners to re-examine the problem with a view toward augmenting port capacities by the use of floating piers and other equipment at the beaches. He also mentioned the possibility of creating sheltered anchorages.17 These were details, he noted, “on which the result of the entire operation in 1944 may turn.”18
The whole problem came into prominence at the end of June at the RATTLE Conference, at which Commodore John Hughes-Hallett, chief naval planner on the COSSAC staff, proposed that the Allies prefabricate their own ports and tow them to the far shore. Preliminary experimentation along these lines had already been undertaken by the Chief of Combined Operations, the Director of Transportation, and the Admiralty, and the concept of artificial ports as they later developed gradually began to crystallize. The RATTLE conferees recognized the need of detailing one officer to coordinate the planning for this project,19 and COSSAC made such a recommendation after the conclusion of the conference.20
The findings and conclusions of the planners finally found formal expression in the outline or digest of the OVERLORD plan presented by COSSAC representatives to the Combined Chiefs at Quebec in August. In general the plan echoed the results of the previous months’ planning with respect to the choice of an assault area, the importance of the availability of sufficient landing ships and craft, and the capacities of beaches and ports in the lodgment area. Among its conclusions
concerning the main conditions affecting the success of the operation it noted that the provision of sheltered waters by artificial means and of special berthing facilities were matters of paramount importance.21
The plan provided for assault landings by three divisions over the Normandy beaches in the vicinity of Caen. Airborne forces were to seize that city with the line Grandcamp–Bayeux–Caen as the D-Day objective. After the beachhead gained sufficient depth and additional troops became available, Allied forces were to execute a turning movement into the Cotentin to capture the major part of Cherbourg. The magnitude of the logistic problem was indicated by the calculation that eighteen divisions would have to be maintained over beaches during the first month of operation, and twelve during the second month, while every captured port, large and small, was being used. The construction of two prefabricated ports (known as MULBERRIES) eventually became a key feature of the final OVERLORD plan.
The planners had also come to a tentative conclusion about subsequent operations to obtain an additional group of ports. They anticipated that after the capture of Cherbourg the Supreme Commander probably would have to make a choice between the Seine ports and the Brittany group as the next major objective. Much would depend on where the enemy concentrated his strength in reaction to the initial landings. Driving east to the Seine ports was regarded as a more ambitious undertaking and an unlikely choice, for it would necessitate forcing the line of the Seine, capturing Paris, and advancing as far as the Somme River in order to cover the development of the Seine ports. To make this attempt prematurely with relatively small resources would be to run the risk of defeat. It was more likely that the Supreme Commander would find it necessary to capture the Brittany and Loire ports first. The latter course would open up sufficient port facilities and permit a build-up of forces, adequately maintained, in preparation for capturing Paris and forcing a passage of the Seine. The successive steps after the initial assault would therefore be to capture Cherbourg, then to drive the enemy as rapidly as possible far enough eastward to secure the left flank of the beachhead, and under this cover to seize the Brittany peninsula.22 This course would make the most economic use of Allied resources. It was important, the planners added, that the Allied forces not outrun their lines of communication, and it was anticipated that after capturing the lodgment they would be forced to halt or limit their operation eastward in order that the lines of communications could be properly established, additional airfields could be restored or built, and considerable quantities of engineer materials sent forward.
Equal in importance to the problem of a rapid build-up and adequate maintenance was the matter of the scale of the assault. Misgivings over the inadequacy of the force were expressed initially at the Quebec Conference in August. Prime Minister Churchill asserted that the scale of the assault was too small and should be strengthened.23 Whether he meant by this augmenting the assault waves or the total force lifted was not at first clear. At any rate, any attempt to enlarge the invasion
force had to contend with the most persistent limiting factor of the entire war—the shortage of landing craft. This problem had come into sharp focus when the COSSAC staff attempted to formulate detailed plans for the size of the assault and build-up forces for OVERLORD. General Morgan had found that barely enough craft would be provided to mount the three assault divisions properly, and that the immediate follow-up force would be most inadequately loaded. He was seriously concerned over a dangerous gap on D plus 1 because of the non-availability of landing craft and the impossibility of combat loading in normal shipping. The hazards of an inadequate follow-up had been demonstrated at Salerno. He felt that there was already “too high a proportion of our goods in the shop window,” and that there was no provision for a floating reserve formation in the real sense of the term. General Morgan’s proposed solution therefore was to strengthen the follow-up (“stocking the back premises” he called it) rather than the assault, and he presented figures on the additional craft needed.24 For several months, however, the COSSAC planners were unable to obtain specific commitments as to the resources which would be made available. Late in September General Morgan complained that the CCS directive placed at his disposal a quantity of landing craft which bore little or no relation to the actual requirements of the proposed operation.
Late in the year the OVERLORD plan was subjected to additional scrutiny by Generals Eisenhower and Montgomery, the newly designated Supreme Commander and ground force commander for OVERLORD respectively. Both were dissatisfied with the proposed scale of the assault, and at the Supreme Commander’s conference on 21 January 1944 General Montgomery pressed for an attack on a wider front. In addition to tactical reasons, there was the all-important need for the early capture of the port of Cherbourg. In considering the approaches to Cherbourg the 21 Army Group commander pointed out that under the currently proposed scheme the marshes and rivers at the base of the Cotentin provided a natural defensive barrier which would undoubtedly delay the drive on the port. It followed that a plan to capture Cherbourg quickly must provide for a landing on the northern side of the barrier (the Douve River). For this reason the area of assault should be extended to include additional beaches on the east Cotentin. It was desirable to widen the landing front for the additional reason that the beachhead was likely to become badly congested. The strongest arguments against this proposed change were put forward by the Allied Naval Commander-in-Chief, Admiral Sir Bertram H. Ramsay, who feared that strengthening the assault would lead to serious congestion in the Southern English ports and would also put a heavy tax on naval resources.25 General Eisenhower had already come to the same conclusions as Montgomery, however, and immediately recommended to the Combined Chiefs an extension of the front and an increase in the assault force from three divisions to five.26
Broadening the attack only created additional demands for shipping, and thus
further aggravated the already chronic shortage in landing craft. Allied planners now estimated that an additional 231 ships and craft would be required to permit the desired widening and enlargement of the assault. The extra shipping could be made available in three ways: cutting down the scales of vehicles carried in the assault and follow-up to provide lift for additional units; postponing the target date one month to allow for additional production; and drawing shipping from the Mediterranean or other sources.
The enlargement of the assault had its most profound impact on plans for launching the ANVIL operation from the south, planning for which was already under way. Since the supply of landing craft was critical in all theaters, and requirements had been figured closely for all needs, it was likely that any appreciable increase in lift for OVERLORD would have to be made at the expense of the southern France operation. ANVIL was designed primarily to assist OVERLORD by creating a diversion to draw off or hold enemy strength, and the possibility of weakening or eliminating it was a matter of strategic import. General Eisenhower hoped to avoid either prospect, since he regarded the operation as an integral part of the OVERLORD invasion design. It was obviously desirable to apply the fullest possible weight of Allied power against the enemy, and the cancellation of ANVIL would mean that seven American and seven French divisions would lie idle in the Mediterranean.27 While the Supreme Commander was fully aware of these implications, he also felt the need for a five-division assault in the north as a minimum to give a favorable chance for success. Experience in Italy had confirmed the conviction that the OVERLORD landing force must be strong enough to achieve quick success, particularly in capturing ports.28
Without attempting an immediate solution of the landing craft problem the Combined Chiefs of Staff at the end of January approved the enlargement of OVERLORD and postponed D Day by one month. Early in February the plan therefore called for an assault by five seaborne divisions on a widened front including the east Cotentin beaches. The U.S. portion of the assault was to be made by the First Army in cooperation with the Western Naval Task Force, one regimental combat team landing between Varreville and the Douve River (UTAH Beach), and two regimental combat teams landing between Vierville and Colleville-sur-Mer (OMAHA Beach). One airborne division was to drop behind UTAH in the initial assault. The first major objective was the capture of Cherbourg.
General Eisenhower was unwavering in his conviction that OVERLORD must be strong enough to preclude any risk of failure, regardless of the effect on ANVIL. Nevertheless, he clung to the hope that the resources might yet be found to launch that operation, directing the planners to work out a compromise shipping plan which would permit the simultaneous launching of the two operations, and postponing a final decision until the middle of March. By that time it became evident that any loading plans employing the available lift were too inflexible for safety and that OVERLORD itself would be endangered by attempting to carry off both operations at the same time. Late in the
month the Supreme Commander reluctantly recommended that the southern operation be canceled as then planned, and some of the shipping in the Mediterranean was transferred to England so that OVERLORD could be mounted in the desired strength. ANVIL did not die, although its future was highly uncertain for the next few months. Despite that uncertainty the boundaries between the European and North African theaters were shifted in March to place southern France within the North African theater’s jurisdiction and responsibility. Switzerland, Hungary, and Austria as well as Vichy France were detached from the ETO. After the Normandy invasion, when the pressure on the available shipping resources was removed, a way was finally found to launch the operation in southern France.29
The OVERLORD plan was revised from time to time until the very date it was launched. Two further amendments are worth noting because of the influence of logistic considerations. One change, made almost concurrently with the extension of the assault area to the east Cotentin, dealt with the employment of airborne forces. General Marshall had voiced an objection to the wide dispersion of airborne forces provided for in the earlier plan, and at a meeting at 21 Army Group headquarters in mid-February this objection was seconded by the top American and British ground force commanders. It is evident from their discussion that the importance of the port problem was firmly riveted in their minds. General Bradley considered that the main object of the early stages of OVERLORD must be to seize Cherbourg as soon as possible and argued that nothing should be allowed to deflect from that aim. His stand was reinforced by General Montgomery, who pointed up the necessity of capturing Cherbourg and then the Brittany and Loire ports in order to secure a lodgment area with an assured maintenance. The attainment of the first objective dictated the greatest possible concentration of strength in the Cotentin, and the final plan accordingly provided for the employment of two American airborne divisions in the Cotentin to facilitate the early capture of Cherbourg. In Montgomery’s view this would be the “main battle.”30
A second revision in the OVERLORD design emphasized even more pointedly the planners’ preoccupation with the far-shore discharge problem. While Cherbourg enjoyed a necessary priority in the port development plans, it was the Brittany group that U.S. forces expected to rely on after the first months on the Continent. The second major objective of OVERLORD was the capture of the Brittany peninsula under the cover of the main body of Allied forces on the left (east) flank. The initial OVERLORD plan anticipated as the first step in the capture of Brittany a thrust southward across the base of the peninsula to seize the ports of Nantes and St. Nazaire at the mouth of the Loire River, followed by operations westward with Brest and the smaller ports of the peninsula as the main objectives. In April 1944 this scheme was revised by the adoption of a supplementary plan known as CHASTITY, under which the capture of Nantes and St. Nazaire was to be deferred. Instead, a major port of entry for U.S.
forces and supplies was to be developed at Quiberon Bay, a large well-protected inlet on the south coast of Brittany approximately midway between the Loire estuary and Lorient.
Several factors influenced this change in plan. In one respect CHASTITY was a further strategic-economic amendment to OVERLORD in that it precluded the necessity for an extensive crossing of a major obstacle, the Loire, and the establishment of a protective bridgehead south of the river, which would have been necessary if the ports of St. Nazaire and Nantes were to be utilized. The capture of such a bridgehead would have required a large number of troops, and would have involved maintenance over a restricted road line of communications from the northern ports. CHASTITY would allow a more economic use of resources which, at best, would be limited in the early phases.
The Quiberon Bay project was also seen as the solution to another major logistic problem. A restudy of port capacities on the Continent revealed that the requirements of the build-up simply would not be met; discharge facilities had to be augmented in some way, particularly in the post-OVERLORD phase, after D plus 90. Nantes and St. Nazaire would in all probability be destroyed. Furthermore, the Normandy beaches were expected to be useful for only a limited period and would be completely abandoned with the advent of bad weather in the fall. Most serious of all would be the inadequate facilities for discharging Liberty ships. Quayside discharge of deep-draft ships such as the Liberties would become a growing necessity as the operation progressed, for it was planned that much of the shallow-draft coaster tonnage would be withdrawn about D plus 42. This would force the use of Liberties, which in turn imposed the necessity of discharging nearly all of the cargo by lighters and amphibious vehicles between D plus 42 and 90. It was essential therefore to have facilities with characteristics required for lighters or berths for deep-draft ships.
The Quiberon Bay area appeared to offer a better solution to the problem than did any other location on the northwest coast of France. Preliminary studies revealed that the area had over 3,000 yards of hard beach of required slope, a sheltered anchorage capable of accommodating about 200 Liberty ships, and four minor ports within easy reach suitable for high-line discharge at first and for deep-water piers later. Furthermore, the Allies could make maximum use of personnel and equipment by concentrating the discharge of cargo in one area instead of dispersing it, and by shortening the haul, thereby decreasing the turn-round of vehicles and increasing their daily tonnage capacity. An excellent road and rail network was known to exist within easy reach of many discharge points around the bay; and the shortened line of haul from the bay direct to army maintenance areas would increase carrying capacity and relieve the overworked network of roads and railways from the Normandy region.
The Quiberon Bay project had certain tactical disadvantages, particularly from the point of view of air and naval protection, but the strategic-logistic advantages of the project outweighed them all, and administrative planners of all the agencies involved became convinced that it was a vital military necessity. The shortage of rail and motor transportation, the practical certainty that the rail net from Brest would be destroyed beyond hope of early repair, the limited capacity of the rail lines
leading southeast from Cherbourg, the unavailability of the Loire ports until a bridgehead was established on the south bank of that river, and the certainty of inadequate port capacity at D plus 90 under the earlier plans all impelled Supreme Headquarters to give its blessing to the scheme, and operational plans were altered to provide for capture of the area by the Third Army.31 Adoption of the Quiberon project in April constituted the last major amendment to the cross-Channel invasion plan.
Adoption of the plan by no means minimized the importance of Brest. It was intended rather to obviate both tactical and logistic disadvantages of earlier plans, and to boost the total port discharge capacity of the Brittany area. The Brittany ports were believed to be so vital logistically that Allied planners began to study the possibility of amphibious and combined amphibious-airborne operations to capture St. Malo, Brest, and Quiberon Bay in the event U.S. forces were unable to advance beyond the neck of the Cherbourg peninsula.32
The evolution of OVERLORD clearly reveals the extent to which logistical factors determined the scale of the assault, the choice of the lodgment area and initial objectives, and the speed of attainment of those objectives. The supply of shipping and the capacity of continental discharge facilities were the most recurrent of the limiting factors, and served as common denominators in all the deliberations over the cross-Channel invasion design. Their importance was clearly evident in the discussions of the Quiberon Bay project. Once the invading forces had secured a foothold on the Continent the most important single strategic objective was to be the capture and development of major ports. These plans had a larger objective, of course—the destruction of enemy forces—but the adequate build-up and proper maintenance of Allied forces were prerequisite to that end.
While the final OVERLORD plan bore strong resemblance to the outline which the COSSAC planners presented to the Combined Chiefs of Staff at Quebec in August 1943, it had undergone important revision through enlargement and strengthening. As finally executed the plan called for amphibious assaults by five divisions on the Normandy coast between the Orne River and the Carentan estuary and on the east coast of the Cotentin peninsula, preceded by airborne landings by one British division near Caen and by two U.S. divisions in the Carentan–Ste. Mère-Eglise area several hours earlier. (Map 5) American seaborne forces were to land on UTAH Beach, on the east coast of the Cotentin in the vicinity of Ste. Mère-Eglise, and on OMAHA Beach, in the vicinity of St. Laurent-sur-Mer. Assault landing craft were to transport three British divisions with attached Commando units, and two U.S. divisions with attached Ranger units. Landing craft and ships for two additional
divisions afloat were to be provided for the follow-up on the second tide of D Day. Heavy air and naval bombardment of enemy forces was to precede the seaborne landings.
OVERLORD called first for a rapid advance inland and in the west the early capture of Cherbourg, to be followed by an eastward expansion of the beachhead to the Eure River from Dreux to Rouen and thence along the Seine to the sea, and the simultaneous seizure of Chartres, Orléans, and Tours. Meanwhile U.S. forces were to drive south to cut off the Brittany peninsula and pave the way for the opening of the Brittany ports and development of Quiberon Bay. Clearance of the area south to the Loire was to complete the mission announced in the OVERLORD plan—the establishment of the lodgment. This was expected to require three months (to D plus 90). The plan made an additional assumption which was to prove historically significant so far as logistic operations were concerned: a pause would probably be necessary upon the completion of the operation to permit the development of the administrative base in preparation for an advance beyond the Seine.