Preparatory Operations for D-Day
Preparatory operations for the Allies invasion on D-Day of Europe.
Preparatory operations incident to the assault were already under way. These were the special concern of the Air Forces and the Navy, and consisted, apart from the Tactical Air Forces' operations already considered, primarily of the strategic bombing of Germany and the Channel exercises designed to afford training to the assault forces.
By a decision taken by the Combined Chiefs of Staff, prior to my arrival in the Theater, command of the strategic bombing forces-the RAF Bomber Command and the United States Strategic Air Forces (composed of the Fifteenth Air Force in the Mediterranean Theater and the Eighth Air Force in the European Theater)ultimately rested with the Combined Chiefs themselves. This decision had been taken with the purpose of coordinating strategic bombing against Germany from all sides. Within the European Theater over-all command of the United States Strategic Air Forces rested with General (then Lieut. Gen.) Carl A. Spaatz and command of the RAF Bomber Command with Air Chief Marshal Sir Arthur Harris. The Strategic Air Forces were thus not under my direct orders, their commanders being instead responsible directly to the Combined Chiefs in Washington. While understanding the long-range motives which brought this decision into being, I was nevertheless dissatisfied with the arrangement, feeling that, since responsibility for the principal effort against Germany fell upon my Headquarters, all the forces to be employed within the Theater-by land, sea, and air-should be responsible to me and under my direction, at least during the critical periods preceding and succeeding the assault.
I stated these views to the Combined Chiefs of Staff. At the same time I set forth the necessity for concentrated bombing of the rail network of Northwest Europe and particularly France, to which there was considerable opposition, the reasons for which will be considered shortly. I felt strongly about both these matters. In a review of the matter, the Combined Chiefs of Staff, who were aware of my problems, gave me operational control of the air forces from 14 April. The Strategic Air Forces after this date were to attack German military, industrial, and economic targets in an order of priority established within the Theater and approved by the Combined Chiefs. Additionally, they were to be available to me upon call for direct support of land and naval operations when needed. This was a role for which they had not previously been normally used, but the Salerno campaign had afforded convincing evidence of their effectiveness for the purpose.
In the final command set-up of the air forces, then, the commanders of the Strategic Air Forces (RAF Bomber Command and the United States Strategic Air Forces) reported to Supreme Headquarters independently as did also Air Chief Marshal Leigh-Mallory, commanding the tactical forces which comprised the Allied Expeditionary Air Force. The effort of the these separate commands was coordinated, under my direction, through the Deputy Supreme Commander, Air Chief Marshal Tedder.
Prior to my arrival in the Theater, the Combined Chiefs of Staff had approved a combined bomber offensive plan against Germany which included the strategic bombing of critical industrial and military targets in the Reich. It had been determined that Germany's vulnerability lay primarily in six industrial systems indispensable to the German war effort: submarines, aircraft, ball bearings, oil, rubber, and communications. Of these six targets, aircraft, oil, and communications became the three which were to occupy the continuing attention of the Strategic Air Forces throughout the war. The bombing attacks upon these targets were to assist materially in weakening the enemy's potentiality to resist our offensives and immeasurably to aid our ground forces in their advance.
An indispensable condition to the success of our Normandy assault was, at the very least, sufficient control of the air to insure the build-up in England and subsequently on the beachhead of our invasion forces and supplies. In anticipation of D-day, therefore, the Allied forces were first concerned with weakening the German Air Force through attacks upon its installations and resources on the ground and on the Force itself in the air. Quite apart from the direct assistance these attacks lent to the success of our landings, they were essential also as a preliminary to the intensive bombing of German industry.
We were aware that the Germans had planned, as far back as July 1942, to develop an air force equal to the task of smashing any invasion. Their aircraft expansion program had as its ultimate goal the production of some 3,000 combat aircraft per month. It was also estimated that the enemy planned to have a first-line strength of 10,000 aircraft, adequately supplied by reserves in depth and a steady flow of replacements. Considerable progress had been made with this program before the growth of Allied aircraft strength in this Theater permitted the intensive scale of air fighting which began in May 1943. Commencing with that date, our attacks upon German aircraft production centers checked the projected increase of manufacture, but the German Air Force was able, nevertheless, to survive 1943 with its front-line strength little changed. In December 1943 the Germans planned to produce 3,000 single engine fighters per month, thus indicating that their production program was influenced as much by the necessity for countering the Allied bombing offensive as for stopping a possible ground invasion.
Beginning in January 1944, however, the assaults upon aircraft production centers were intensified and the effect of these attacks was such that the German Air Force had been robbed by midsummer of most of its production capacity and also deprived of the adequate reserves necessary to maintain its front-line strength. These conditions resulted not only from damage to production centers but also from such other factors as attrition of aircraft and crews in air battles, shortage of aviation gasoline for training purposes, and disruption of communications. As the invasion date approached, a clear sign of our superiority in the air was the obvious unwillingness of the enemy to accept the challenge to combat which we initiated with large scale fighter sweeps over his territory. Our D-day experience was to convince us that the carefully laid plans of the German High Command to oppose OVERLORD with an efficient air force in great strength were completely frustrated by the strategic bombing operations. Without the overwhelming mastery of the air which we attained by that time our assault against the Continent would have been a most hazardous, if not impossible, undertaking.
This mastery of the air was maintained throughout 1944 and 1945 by continuing attacks against production centers. But the enemy was able, through factory reconstruction and dispersal, together with the development of jet aircraft, to maintain into 1945 a fighter force of a theoretical strength by no means negligible. Nevertheless, it still was not qualitatively good and proved incompetent to perform successfully for any substantial period any of the normal missions of an air force.
By D-day the Strategic Air Forces together with the Tactical Air Forces had so successfully performed their mission of disrupting enemy communications that there was a chronic shortage of locomotives and cars, repair facilities were inadequate, coal stocks were reduced to a six days' supply, and 74 bridges and tunnels leading to the battle area were impassable. The communications chaos thus produced had fatal effects upon the enemy's attempts at reinforcement after our landings.
The initial attacks upon the communications system in France were undertaken as the result of an extremely difficult decision for which I assumed the full responsibility. I was aware that the attacks upon the marshaling yards and rail centers, by both the Strategic and Tactical Air Forces, would prove costly in French lives. In addition, a very important part of the French economy would for a considerable period be rendered useless. On separate occasions both Prime Minister Churchill and General Koenig, Commander of the French Forces of the Interior, asked that I reconsider my decision to bomb these particular targets. General Koenig requested once that he be permitted to participate as a member of a review board to determine the relative necessity of bombing centers of population; with regard to the loss of French lives, however, he took a stern and soldierly attitude, remarking: "It is war." I was aware of all the implications inherent in my decision, even of the heart-rending possibility that our French Allies might be alienated from us. Nevertheless, for purely military reasons, I considered that the communications system of France had to be disrupted. The fate of a continent depended upon the ability of our forces to seize a foothold and to maintain that foothold against everything we expected the enemy to throw against us. No single factor contributing to the success of our efforts in Normandy could be overlooked or disregarded. Military events, I believe, justified me decision taken, and the French people, far from being alienated, accepted me hardships and suffering with a realism worthy of a far-sighted nation.
With mastery of the air achieved in me spring of 1944, it became more readily possible for the Allied Strategic Air Forces to concentrate their power overwhelmingly against the declining oil reserves of Germany. The attack against the German oil industry commenced in April and continued until the termination of operations. Within the first month of attack German production fell to 80 percent of its previous normal capacity, and by December 1944 it had fallen to a mere 30 percent. This 30 percent itself was only produced as the result of herculean efforts which diverted manpower and labor hours from other equally essential industries, such as, for example, the production of the new and ingenious weapons of war with which Germany hoped to decide the issue of the conflict.
The subsequent shortage of oil brought on by our operations contributed to the complete collapse of me German bomber force and must have had its effect upon me decline of the U-boat menace. Immobility from oil shortage caused the capture of tens of thousands 16 of German soldiers and the destruction of their vehicles. Lack of oil and communications shattered by air bombardment retarded divisions arriving to reinforce the Normandy front in June. By December, when von Rundstedt's forces attacked in the Battle of the Ardennes, many units had to set out with extremely limited supplies of fuel, hoping desperately to overrun our positions so quickly that captured stocks would support their further advance. Within Germany the oil situation was so desperate that the recovery and repair program for the shattered industry was given the highest priority in tile national war effort, above aircraft and submarine production and all other activities.
In addition to the strategic bombing of oil, aircraft, and communications targets, we were, during the campaign, to call upon the Strategic Air Forces for tactical support. At the time of me breakthrough in Normandy and several times later, including the Battle of the Ardennes, strategic bombers were employed in strength to attack enemy positions, supply bases immediately supporting the enemy front, and strong points and communication centers within the battle area. In these instances of tactical assistance, the Strategic Air Forces aided immeasurably in turning the decision of battle in our favor.
While the preparatory air operations of both the Strategic and Tactical Air Forces were growing in intensity as D-day approached, the naval and assault forces were engaged in Channel exercises designed not only to afford final training to the troops and crews but also to test enemy reaction to our mounting preparations. During the assembly of the five assault forces in the areas of Plymouth, Portland, Portsmouth, Southampton, and the Isle of Wight which was completed on 26 April, considerable enemy E-boat activity was noted which was primarily reconnaissance rather than offensive in nature. On 26 April the first full-scale exercise, TIGER, involving Force "U" under the command of Admiral Moon, took place from the Plymouth area. Owing to me fact that one of the escorting destroyers was damaged in a collision during the night of 26/27 April and was not on hand when the assault convoy was attacked by E-boats, mere was an unfortunate loss of life in the sinking of two LST's. In other respects the exercises were successful and valuable lessons were learned, relating not only to the movement and handling of the task force ships but also to me assault against beaches. Areas such as Slapton Sands in southwest England, similar to those which the troops would encounter in France, were used for practice purposes.
Subsequent to Exercise TIGER, further Channel exercises involving the other task forces were undertaken during the first week of May. Considerable enemy reaction had been anticipated, but the exercises proceeded without any undue interference or even attention from the enemy. In certain cases it seemed apparent that he lacked information as to the extent and nature of the exercises. Our air superiority had driven his reconnaissance planes from the skies, the watch kept by our naval forces was unceasing, and the security precautions taken effectively neutralized the efforts of any agents whom he may have employed. Following the E-boat attack upon Force "U," the German radio had, for example, simply announced that ships of a Channel convoy had been torpedoed and sunk, indicating that the German command was unaware that the ships were assault craft and not the usual merchant ships in convoy. We also knew that the enemy was aware in other instances of our purposes, but preferred to reserve his forces for use on D-day itself rather than to expend them against local exercises.
Enemy Capabilities on D-Day