[Attachment to Annex B]
Memorandum by the Chief of
Staff to the Supreme Allied Commander
Designate (Morgan)
most secret
C.O.S.S.A.C. (43) 32
(Final)
C.O.S. (43) 415 (O)
[
London,]
27th July,
1943.
4
Digest of Operation “Overlord”
object
1. The object of Operation “
Overlord
” is to mount and carry out an operation, with forces
und equipment established in the United Kingdom, and with target
date the 1st May, 1944, to secure a lodgement on the Continent
from which further offensive operations can be developed. The
lodgement area must contain sufficient port facilities to
maintain a force of some twenty-six to thirty divisions, and
enable that force to be augmented by follow-up shipments from
the United States or elsewhere of additional divisions and
supporting units of the rate of three to five divisions per
month.
selection of a lodgement area
2. In order to provide sufficient port facilities to maintain
these large forces, it will be necessary to select a lodgement
area which includes a group of major ports. We must plan on the
assumption that ports, on capture, will be seriously damaged and
probably blocked. It will take some time to restore normal
facilities. We shall thus be forced to rely on maintenance over
beaches for an extended period.
3. A study of the beaches on the Belgian and Channel coasts shows
that the beaches with the highest capacity for passing vehicles
and
[Page 489]
stores inland are
those in the Pas de Calais,*
and the Caen†–Cotentin‡ area. Of
these, the Caen beaches are the most favourable, as they are,
unlike the others, sheltered from the prevailing winds. Naval
and air considerations point to the area between the Pas de
Calais and the Cotentin as the most suitable for the initial
landing, air factors of optimum air support and rapid provision
of airfields indicating the Pas de Calais as the best choice,
with Caen as an acceptable alternative.
4. Thus, taking beach capacity and air and naval considerations
together, it appears that either the Pas de Calais area or the
Caen–Cotentin area is the most suitable for the initial main
landing.
5. As the area for the initial landing, the Pas de Calais has
many obvious advantages such that good air support and quick
turn round for our shipping can be achieved. On the other hand,
it is a focal point of the enemy fighters disposed for defence,
and maximum enemy air activity can be brought to bear over this
area with the minimum movement of his air forces. Moreover, the
Pas de Calais is the most strongly defended area on the whole
French coast. The defences would require very heavy and
sustained bombardment from sea and air: penetration would be
slow, and the result of the bombardment of beach exits would
severely limit the rate of build-up. Further, this area does not
offer good opportunities for expansion. It would be necessary to
develop the bridgehead to include either the Belgian ports as
far as Antwerp or the Channel ports Westwards to include Havre
and Rouen. But both an advance to Antwerp across the numerous
water obstacles, and a long flank march of some 120 miles to the
Seine ports must be considered unsound operations of war unless
the German forces are in a state not far short of final
collapse.
6. In the Caen–Cotentin area it would be possible to make our
initial landing either partly on the Cotentin Peninsula and
partly on the Caen beaches, wholly in the Cotentin or wholly on
the Caen beaches. An attack with part of our forces in the
Cotentin and part on the Caen beaches is, however, considered to
be unsound. It would entail dividing our limited forces by the
low-lying marshy ground and intricate river system at the neck
of the Cotentin Peninsula; thus exposing them to defeat in
detail.
7. An attack against the Cotentin Peninsula, on the other hand,
has a reasonable chance of success, and would ensure the early
capture of the port of Cherbourg., Unfortunately, very few
airfields exist in the
[Page 490]
Cotentin, and that area is not suitable for rapid airfield
development. Furthermore, the narrow neck of the Peninsula would
give the Germans an easy task in preventing us from breaking out
and expanding our initial bridgehead. Moreover, during the
period of our consolidation in the Cotentin the Germans would
have time to reinforce their coastal troops in the Caen area,
rendering a subsequent amphibious assault in that area much more
difficult.
8. There remains the attack on the Caen beaches. The Caen sector
is weakly held; the defences are relatively light and the
beaches are of high capacity and sheltered from the prevailing
winds. Inland the terrain is suitable for airfield development
and for the consolidation of the initial bridgehead; and much of
it is unfavourable for counterattacks by Panzer divisions. Maximum enemy air opposition can
only be brought to bear at the expense of the enemy air defence
screen covering the approaches to Germany; and the limited
number of enemy airfields within range of the Caen area
facilitates local neutralisation of the German fighter force.
The sector suffers from the disadvantage that considerable
effort will be required to provide adequate air support to our
assault forces and some time must elapse before the capture of a
major port.
After a landing in the Caen sector it would be necessary to seize
either the Seine group of ports or the Brittany group of ports.
To seize the Seine ports would entail forcing a crossing of the
Seine, which is likely to require greater forces than we can
build up through the Caen beaches and the port of Cherbourg. It
should, however, be possible to seize the Brittany ports between
Cherbourg and Nantes and on them build up sufficient forces for
our final advance Eastwards.
Provided that the necessary air situation can first be achieved,
the chances of a successful attack and of rapid subsequent
development are so much greater in this sector than in any other
that it is considered that the advantages far outweigh the
disadvantages.
the lodgement area selected
9. In the light of these factors, it is considered that our
initial landing on the Continent should be effected in Caen
area, with a view to the eventual seizure of a lodgement area
comprising the Cherbourg–Brittany group of ports (from Cherbourg
to Nantes).
opening phase up to the capture of
cherbourg
10. The opening phase in the seizing of this lodgement area would
be the effecting of a landing in the Caen sector with a view to
the early capture and development of airfield sites in the Caen
area, and of the port of Cherbourg.
[Page 491]
11. The main limiting factors affecting such an operation are the
possibility of attaining the necessary air situation; the number
of offensive divisions which the enemy can make available for
counter attack in the Caen area; the availability of landing
ships and craft and of transport aircraft; and the capacity of
the beaches and ports in the sector.
12. Although the strength of the G.A.F. available in 1944 on the Western front
cannot be forecast at this stage, we can confidently expect that
we shall have a vast numerical superiority in bomber forces. The
first-line strength of the German fighter force is, however,
showing a steady increase and although it is unlikely to equal
the size of the force at our disposal, there is no doubt that
our fighters will have a very large commitment entailing
dispersal and operations at maximum intensity. Our fighters will
also be operating under serious tactical disadvantages in the
early stages, which will largely offset their numerical
superiority. Before the assault takes place, therefore, it will
be necessary to reduce the effectiveness of the G.A.F., particularly that part
which can be brought to bear against the Caen area.
13. The necessary air situation to ensure a reasonable chance of
success will therefore require that the maximum number of German
fighter forces are contained in the Low Countries and North-West
Germany, that the effectiveness of the fighter defence in the
Caen area is reduced and that air reinforcements are prevented
from arriving in the early stages from the Mediterranean. Above
all, it will be necessary to reduce the over-all strength of the
German fighter force between now and the date of the operation
by destruction of the sources of supply, by the infliction of
casualties by bringing on air battles, and, immediately prior to
the assault, by the disorganisation of G.A.F. installations and control system in the Caen
area.
14. As it is impossible to forecast with any accuracy the number
and location of German formations in reserve in 1944, while, on
the other hand, the forces available to us have been laid down,
an attempt has been made in this paper to determine the wisest
employment of our own forces and then to determine the maximum
number of German formations which they can reasonably overcome.
Apart from the air situation, which is an over-riding factor,
the practicability of this plan will depend principally on the
number, effectiveness and availability of German divisions
present in France and the Low Countries in relation to our own
capabilities. This consideration is discussed below (paragraph
35).
15. A maximum of thirty and a minimum of twenty-six equivalent
divisions are likely to be available in the United Kingdom for
cross
[Page 492]
Channel
operations on the 1st May 1944. Further build-up can be at the
rate of three to five divisions per month.
16. Landing ships and craft have been provided to lift the
equivalent of three assault divisions and two follow-up
divisions, without “overheads,” and it has been assumed that the
equivalent of an additional two divisions can be afloat in
ships.
17. Airborne forces amounting to two airborne divisions and some
five or six parachute regiments will be available, but, largely
owing to shortage of transport aircraft, it is only possible to
lift the equivalent of two-thirds of one airborne division
simultaneously, on the basis of present forecasts.
18. Even if additional landing ships and craft could be made
available, the beaches in the Caen area would preclude the
landing of forces greater than the equivalent of the three
assault and two follow-up divisions, for which craft have
already been provided. Nevertheless, an all-round increase of at
least 10 per cent in landing ships and craft is highly desirable
in order to provide a greater margin for contingencies within
the framework of the existing plan. Furthermore, sufficient lift
for a further assault division could most usefully be employed
in an additional landing on other beaches,
19. There is no port of any capacity within the sector although
there are a number of small ports of limited value. Maintenance
will, therefore, of necessity be largely over the beaches until
it is possible to capture and open up the port of Cherbourg. In
view of the possibilities of interruption by bad weather it will
be essential to provide early some form of improvised sheltered
waters,
20. Assuming optimum weather conditions, it should be possible to
build up the force over the beaches to a total by D plus 6 of the equivalent of some
eleven divisions and five tank brigades and thereafter to land
one division a day until about D plus
24.
proposed plan
Preliminary Phase.
21. During the preliminary phase, which must start forthwith, all
possible means including air and sea action, propaganda,
political and economic pressure, and sabotage, must be
integrated into a combined offensive aimed at softening the
German resistance. In particular, air action should be directed
towards the reduction of the German air forces on the Western
front, the progressive destruction of the German economic system
and the undermining of German morale.
22. In order to contain the maximum German forces away from the
Caen area diversionary operations should be staged against other
areas such as the Pas de Calais and the Mediterranean Coast of
France.
[Page 493]
Preparatory Phase.
23. During this phase air action will be intensified against the
G.A.F., particularly in
North-West France, with a view to reducing the effectiveness of
the G.A.F. in that area, and
will be extended to include attacks against communications more
directly associated with movement of German reserves which might
affect the Caen area. Three naval assault forces will be
assembled with the naval escorts and loaded at ports along the
South Coast of England. Two naval assault forces carrying the
follow-up forces will also be assembled and loaded, one in the
Thames Estuary and one on the West Coast.
The Assault.
24. After a very short air bombardment of the beach defences
three assault divisions will be landed simultaneously on the
Caen beaches, followed up on D
day by the equivalent of two tank brigades (United
States regiments) and a brigade group (United States regimental
combat team). At the same time, airborne forces will be used to
seize the town of Caen; and subsidiary operations by commandos
and possibly by airborne forces will be undertaken to neutralise
certain coast defences and seize certain important river
crossings. The object of the assault forces will be to seize the
general line of Grandcamp–Bayeux–Caen.
Follow-up and Build-up Phase.
25. Subsequent action will take the form of a strong thrust
Southwards and South-Westwards with a view to destroying enemy
forces, acquiring sites for airfields, and gaining depth for a
turning movement into the Cotentin Peninsula directed on
Cherbourg. When sufficient depth has been gained a force will
advance into the Cotentin and seize Cherbourg. At the same time
a thrust will be made to deepen the bridgehead South-Eastwards
in order to cover the construction and operation of additional
airfields in the area South-East of Caen.
26. It is considered that, within fourteen days of the initial
assault, Cherbourg should be captured and the bridgehead
extended to include the general line Trouville–Alençon–Mont St.
Michel. By this date, moreover it should have been possible to
land some eighteen divisions and to have in operation about
fourteen airfields from which twenty-eight to thirty-three
fighter-type squadrons should be operating.
further developments after capture of
Cherbourg
27. After the capture of Cherbourg the Supreme Allied Commander
will have to decide whether to initiate operations to seize the
Seine ports or whether he must content himself with first
occupying the Brittany ports. In this decision he will have to
be guided largely by
[Page 494]
the situation of the enemy forces. If the German resistance is
sufficiently weak, an immediate advance could be made to seize
Havre and Rouen. On the other hand, the more probable situation
is that the Germans will have retired with the bulk of their
forces to hold Paris and the line of the Seine, where they can
best be covered by their air forces from North-East France and
where they may possibly be reinforced by formations from Russia.
Elsewhere they may move a few divisions from Southern France to
hold the crossings of the Loire and will leave the existing
defensive divisions in Brittany.
It will therefore most probably be necessary for us to seize the
Brittany ports first, in order to build up sufficient forces
with which we can eventually force the passage of the Seine.
28. Under these circumstances, the most suitable plan would
appear to be to secure first the left flank and to gain
sufficient airfields for subsequent operations. This would be
done by extending the bridgehead to the line of the River Eure
from Dreux to Rouen and thence along the line of the Seine to
the sea, seizing at the same time Chartres, Orléans and
Tours.
29. Under cover of these operations a force would be employed in
capturing the Brittany ports; the first step being a thrust
Southwards to seize Nantes and St. Nazaire, followed by
subsidiary operations to capture Brest and the various small
ports of the Brittany Peninsula.
30. This action would complete the occupation of our initial
lodgement area and would secure sufficient major ports for the
maintenance of at least thirty divisions. As soon as the
organisation of the L. of C. in
this lodgement area allowed, and sufficient air forces had been
established, operations would then be begun to force the line of
the Seine, and to capture Paris and the Seine ports. As
opportunity offered, subsidiary action would also be taken to
clear the Germans from the Biscay ports to facilitate the entry
of additional American troops and the feeding of the French
population.
command and control
31. In carrying out Operation “
Overlord
” administrative control would be greatly simplified if
the principle were adopted that the United States forces were
normally on the right of the line and the British and Canadian
forces on the left.
major conditions affecting success of the
operation
32. It will be seen that the plan for the initial landing is
based on two main principles—concentration of force and tactical
surprise. Concentration of the assault forces is considered
essential if we are to ensure adequate air support and if our
limited assault forces are to avoid defeat in detail. An attempt
has been made to obtain tactical
[Page 495]
surprise by landing in a lightly defended
area—presumably lightly defended as, due to its distance from a
major port, the Germans consider a landing there unlikely to be
successful. This action, of course, presupposes that we can
offset the absence of a port in the initial stages by the
provision of improvised sheltered waters. It is believed that
this can be accomplished.
33. The operation calls for a much higher standard of performance
on the part of the naval assault forces than any previous
operation. This will depend upon their being formed in
sufficient time to permit of adequate training.
34. Above all, it is essential that there should be an over-all
reduction in the German fighter force between now and the time
of the surface assault. From now onwards every practical method
of achieving this end must be employed. This condition, above
all others, will dictate the date by which the amphibious
assault can be launched.
35. The next condition is that the number of German offensive
divisions in reserve must not exceed a certain figure on the
target date if the operation is to have a reasonable chance of
success. The German reserves in France and the Low Countries as
a whole, excluding divisions holding the coast, G.A.F. divisions and training
divisions, should not exceed on the day of the assault twelve
full-strength first-quality divisions. In addition, the Germans
should not be able to transfer more than fifteen first-quality
divisions from Russia during the first two months. Moreover, on
the target date the divisions in reserve should be so located
that the number of first-quality divisions which the Germans
could deploy in the Caen area to support the divisions holding
the coast should not exceed three divisions on D day, five divisions by D plus 2, or nine divisions by D plus 8.
During the preliminary period, therefore, every effort must be
made to dissipate and divert German formations, lower their
fighting efficiency and disrupt communications.
36. Finally, there is the question of maintenance. Maintenance
will have to be carried out over beaches for a period of some
three months for a number of formations, varying from a maximum
of eighteen divisions in the first month to twelve divisions in
the second month, rapidly diminishing to nil in the third month.
Unless adequate measures are taken to provide sheltered waters
by artificial means, the operation will be at the mercy of the
weather. Moreover, special facilities and equipment will be
required to prevent undue damage to craft during this extended
period. Immediate action for the provision of the necessary
requirements is essential.
37. Given these conditions—a reduced G.A.F., a limitation in the number or effectiveness
of German offensive formations in France,
[Page 496]
and adequate arrangements to
provide improvised sheltered waters—it is considered that
Operation “
Overlord
” has a reasonable prospect of success. To ensure these
conditions being attained by the 1st May, 1944, action must
start now and every possible effort made
by all means in our power to soften German resistance and to
speed up our own preparations.5
Offices of the War Cabinet, S.W.1,
30th July 1943.
