Office of the Historian

J.C.S. Files

Study by the United States Joint Staff Planners1

secret
Enclosure to C.C.S. 215
[Washington,] 13 May 1943.

Invasion of the European Continent From the United Kingdom in 1943–1944

1.
A detailed examination of the merits and possibilities of the defeat of the European Axis by a bomber offensive and air-ground invasion of the Continent from the United Kingdom has been made by the U. S. Chiefs of Staff.
2.
It is estimated that Germany has 32 divisions in France and the low countries. Seven of these divisions are highly mobile and could on short notice be moved to oppose an invasion effort. These forces could be increased in time to a grand total of 60 divisions. She also has about 1254 planes in the area (747 fighters) which could be increased to 1766 (1158 fighters) by stripping all areas except the Mediterranean and Eastern Front, In addition to a coastal defense zone varying from 5 to 15 miles in depth, she has four defensive belts which must be reduced or neutralized before the West Wall is reached.
3.
The projected bomber offensive against Germany may be expected to so reduce her ability to wage war as to create favorable conditions for a reentry to the Continent unless Germany is able to develop timely and effective counter-measures.
4.
By maximum utilization of shipping and United Kingdom port facilities for the movement of United States forces, and by placing increased emphasis on the conversion of British defensive divisions into offensive units, it is estimated that 36 United Nations Divisions can be made available for cross-Channel operations by 1 April 1944.
5.
Whether the available shipping is used to move forces from the United States or the Mediterranean, the total number of divisions available in the United Kingdom will be the same. However, the addition of battle seasoned troops from the Mediterranean will provide an added insurance for the success of the initial assault.
6.
The two most promising areas for assault operations, the Caen and Cotentin Peninsula sectors, will afford port facilities for a build-up [Page 239] in 12 months of about 1,000,000 men. By extending this bridgehead to include the Seine River and the ports of Le Havre and Rouen, the build-up in 12 months would be about 4,000,000 men, or about 100 divisions.
7.
It should be noted that consideration of cross-Channel operations in this study has been confined to the initial movement. Landing craft for this purpose as compared with the requirements of C.C.S. 105/22 may be met, but at the expense of some operations in other theaters. The build-up immediately thereafter and the requirements in APA’s, AKA’s, AP’s, AK’s, etc., have not been examined.
8.
It is recommended that:
a.
The combined bomber offensive be given first priority in buildup and its execution be facilitated.
b.
As the combined bomber offensive progresses, its effects should be continuously examined and integrated with other factors, the results of these examinations to be used in determining the date for cross-Channel operations.
c.
A balanced invasion force be built up in the United Kingdom as rapidly as possible for the purpose of an early invasion in the event of a collapse of Germany ( Sledgehammer ).
d.
No operations be undertaken in the Mediterranean which will interfere with the build-up of maximum forces in the United Kingdom for Sledgehammer as well as for Roundup .
e.
Production of landing craft be increased to the maximum without undue interference with the construction of other essential war materials.
f.
The target date of 1 April 1944 be accepted for operations from the United Kingdom. The target date coincides with the completion of the fourth phase of the bomber offensive and is subject to revision in the light of the results obtained.
  1. At the meeting of the Combined Chiefs of Staff on May 15, 1943, Leahy stated that this paper would be circulated for the information of the British Chiefs of Staff; see ante, p. 82. Although dated May 13, this paper was circulated to the Combined Chiefs of Staff on May 15 under cover of the following memorandum by the United States Chiefs of Staff: “The enclosed study [w]as prepared by the United States Joint Staff Planners and meets with the approval of the United States Chiefs of Staff. It is submitted for consideration by the Combined Chiefs of Staff.” Final action on the subject dealt with in this paper was taken in C.C.S. 242/6, May 25, 1943, “Final Report to the President and Prime Minister,” post, p. 364.↩
  2. Not printed; regarding the nature of the C.C.S. 105 series, on landing-craft deliveries, see Leighton and Coakley, pp. 483–484.↩