The first COSSAC plan for D-Day, was presented to the Allied war leaders at Quebec in May 1943. Lieutenant General F E Morgan, as head of COSSAC, was given the task of presenting this plan. Morgan was to explain the plan in writing to the War Cabinet in July 1943.........
Chiefs of Staff Committee,
Offices of the War Cabinet.
15th July 1943.
1. In my original Directive (C.O.S. (43) 215 (O)) I was charged with the duty of preparing a plan for a full scale assault against the Continent in 1944 as early as possible.
2. This part of my Directive was subsequently amplified (see C.O.S. (43) 113th Meeting (O), Item 4), in that I was ordered to submit an outline plan for an assault, with certain specified forces, on a target date the 1st May, 1944, to secure a lodgement on the Continent from which further offensive operations can be carried out. It was indicated to me, in the course of this amplification, that the lodgement area should include ports that, suitably developed, could be used by ocean-going ships for the build-up of the initial assault forces from the United Kingdom, and for their further build-up with additional divisions and supporting units that might be shipped from the United States or elsewhere.
3. I have the honour now to report that, in my opinion, it is possible to undertake the operation described, on or about the target date named, with the sea, land and air forces specified, given a certain set of circumstances in existence at that time.
4. These governing circumstances are partly within our direct control and partly without. Those within our control relate first to the problem of beach maintenance, and secondly to the supply of shipping, naval landing craft and transport aircraft. Wherever we may attempt to land, and however many ports we capture, we cannot escape the fact that we shall be forced to maintain a high proportion of our forces over the beaches for the first two or three months while port facilities are being restored; and that, in view of the variability of the weather in the Channel, this will not be feasible unless we are able rapidly to improvise sheltered anchorages off the beaches. New methods of overcoming this problem are now being examined. There is no reason to suppose that these methods will be ineffective, but I feel it my duty to point out that this operation is not to be contemplated unless this problem of prolonged cross-beach maintenance and the provision of artificial anchorages shall have been solved.
5. As regards the supply of shipping, naval landing craft and transport aircraft, increased resources in these would permit of the elaboration of alternative plans designed to meet more than one set of extraneous conditions, whereas the state of provision herein taken into account dictates the adoption of one course only, or none at all. In proportion as additional shipping, landing craft and transport aircraft can be made available, so the chances of success in the operation will be increased. It seems feasible to contemplate additions as a result either of stepped-up production, of strategical re-allotment or, in the last resort, of postponement of the date of assault.
6. I have come to the conclusion that, in view of the limitations in resources imposed by my directives, we may be assured of a reasonable chance of success on the 1st May, 1944, only if we concentrate our efforts on an assault across the Norman beaches about Bayeux.
7. As regards circumstances that we can control only indirectly, it is, in my opinion, necessary to stipulate that the state of affairs existing at the time, both on land in France and in the air above it, shall be such as to render the assault as little hazardous as may be so far as it is humanly possible to calculate. The essential discrepancy in value between the enemy's troops, highly organised, armed and battle-trained, who await us in their much vaunted impregnable defences, and our troops, who must of necessity launch their assault at the end of a cross-Channel voyage with all its attendant risks, must be reduced to the narrowest possible margin. Though much can be done to this end by the means available and likely to become available to us in the United Kingdom to influence these factors, we are largely dependent upon events that will take place on other war fronts, principally on the Russian front, between now and the date of the assault.
8. I therefore suggest to the Chiefs of Staff that it is necessary, if my plan be approved, to adopt the outlook that Operation "Overlord" is even now in progress, and to take all possible steps to see that all agencies that can be brought to bear are, from now on, co-ordinated in their action as herein below described, so as to bring about the state of affairs that we would have exist on the chosen day of assault.
9. Finally, I venture to draw attention to the danger of making direct comparisons between operation "Husky"* and operation "Overlord." No doubt the experience now being gained in the Mediterranean will prove invaluable when the detailed planning stage for "Overlord" is reached, but viewed as a whole the two operations could hardly be more dissimilar. In "Husky," the bases of an extended continental coastline were used for a converging assault against an island, whereas in "Overlord" it is necessary to launch an assault from an island against an extended continental mainland coastline. Furthermore, while in the Mediterranean the tidal range is negligible and the weather reasonably reliable, in the English Channel the tidal range is considerable and the weather capricious.
10. Attached hereto are papers setting forth the plan that I recommend for adoption.F.E. MORGAN, Lieutenant-General,
* = the operation in Sicily going on when the letter was written