Air Fronts: Theaters of Operation - European Theater of Operation: Sunday Punch in Normandy - Transition
Wings at War Series, No. 2 ; Sunday Punch in Normandy. THE TACTICAL USE OF HEAVY BOMBARDMENT IN THE NORMANDY INVASION: An Interim Report; Published by Headquarters, Army Air Forces Washington, D. C., Office of Assistant Chief of Air Staff, Intelligence, From Reports Prepared by Eighth Air Force. CONFIDENTIAL. US GPO 1945. (declassified)
Transition From a Strategic to a Tactical Role
Heavy-bomber operations in close cooperation with ground forces involved a tactical concept differing greatly from familiar strategic bombing activities. Problems were posed in relation to assemblies, formations, routings, bomb loadings, fuzings, and overcast bombing techniques; details of briefing and mission reporting had to be worked out; coordination with other air forces and with naval planners was necessary to a far greater degree than heretofore required; aircraft recognition and delineation of prohibited bombing zones had to be considered. Most important, the requirements of the ground forces must be translated into a workable air cooperation program, and the ground force commanders had to be thoroughly informed as to the capabilities and the limitations of the heavy bombers. Differences arose and were generally compromised, although a few were submitted to SHAEF for final settlement. The over-all plan was of such paramount importance that practice exercises were necessary to settle many points, often on a large scale and sometimes integrated with the execution of operational flights. Rehearsals of certain features of the program were undertaken to assure successful performance at the critical time. The more important problems, and the steps taken to solve them, were:
Predawn assembly
The initial D-day bomber program called for take-off and assembly during hours of darkness on an unprecedented scale. It was believed that the use of radio aids, flares, and navigation lights would permit successful accomplishment, but it was deemed wise to have a trial operation. This was conducted on 1 May before a regular bombing mission. It involved nine groups of 21 aircraft each from each of the three bombardment divisions, with aircraft assembling in specified areas during the hours of darkness and following designated routes to the south coast and back to the base areas. The aircraft in each group were dispatched in three waves, the first composed of nine-plane squadrons and the second and third of six-plane squadrons. The exercise was completely satisfactory, and on the basis of this test the six-plane squadron was adopted for the D-day missions.
Routings
While the usual consideration of route planning prevailed, the necessity of assuring recognition of aircraft by naval vessels employed on convoy operations resulted in placing restrictions on flights over the shipping lanes. One of these forbade any aircraft except fighters on shipping patrol to fly over the convoy areas from the direction of the combat zones or the Pas de Calais. Because of this, and in connection with the use of Pathfinder equipment, it was decided to prescribe a course for the initial D-day mission directly from the south coast of England to the Normandy beaches and returning south and west of the Channel Isles.
Loadings and fuzings
Extensive research was conducted to determine the types of bombs and fuzings to be used. An AEAF Weapons Committee, with four representatives of the Eighth Air Force, was established to consider these questions, and several practice bombing missions were conducted, the most comprehensive being held on 26 April, in which 12 nine-plane flights were sent to the Studland Bay bombing range to determine the effect of 100-, 250-, and 500-lb. bombs with various fuzings. It was learned that fragmentation and 100-lb. HE bombs would be most effective against personnel, vehicles, wire entanglements, and gun positions not emplaced. Recommendations based on these findings were incorporated in the over-all air plan.
Overcast bombing technique
The possibility of having to use Pathfinder instruments for initial D-day bombing missions was considered, and the relative merits of both H2X and GH were weighed. On the basis of operational experience and tests the former was selected. This decision resulted from the lower average range error to be expected from H2X as compared with GH when the former was operating against targets located in such a manner that water and land appeared simultaneously on the scope at right angles to the line of approach, the definition in such instances being particularly clear. This factor was an important consideration in the selection of the north-south approach. Deflection errors did not constitute hazards on this axis of attack. The limited number of GH aircraft available was a further consideration, since accuracy would be seriously impaired if a very large number of units was releasing on relatively few Pathfinders, and the possibility of equipment failures on these few Pathfinders would have a proportionately large effect on results.
Visibility trials
Accurate determination of earliest and latest times practicable for visual bombing was of vital import to the exact establishment of H-hour. A visibility trial was conducted by aircraft of the Eighth Air Force, the Ninth Air Force, and the 2d Tactical Air Force, operating against simulated targets in England (an infantry platoon, field artillery battery, coastal battery, small village, roads in open and wooded areas, railway lines, and coastal and inland towns). Results of this operation were forwarded to Headquarters, AEAF, on 24 May 1944 for use in the determination of H-hour.
Briefing and interrogation
The security aspect was a primary consideration of the briefing, and it was decided that efficiency would not be impaired if air crews were not given the essential information prior to the normal pre-mission briefing. Exception was made in the case of Pathfinder navigators and bombardiers, who were specially briefed some days in advance. At the briefing, stress was laid on the importance of avoiding premature bomb releases because of the tremendous Allied assemblage off-shore. Normal time limits for interrogation and submitting mission reports were revised in the interest of expediting the flow of information regarding results and observations. A system of tactical reporting was accordingly set up whereby preliminary reports were to reach Eighth Air Force Headquarters within 45 minutes after first landings and detailed intelligence reports within 2 hours. A comprehensive staff coordination trial was held involving the issuance of specimen field orders, briefing for three simulated D-day missions, fictitious take-off and landing times, and flash and intelligence reports.
BEACH SCENE. In this oblique view of one of the Normandy invasion beaches it is possible to see the blast damage resultant from the bomb carpet spread before the assaulting ground forces.
Aircraft recognition and demarcation of friendly lines
The dangers inherent in the inability of Allied units-air, sea, and ground-to ascertain without delay the hostile or friendly character of combat aircraft were recognized and precautionary steps were taken. Prohibited zones for certain types of aircraft were established, principally over the shipping lanes and assault area, thus allowing naval and ground forces unrestricted freedom to fire at aircraft other than stated types or approaching from other than certain directions.
Another measure was the institution of distinctive markings for aircraft. Except the four-engine bombers, all planes were painted with wide alternate black and white stripes on wings and fuselage. The converse problem of defining areas for combat aircraft in order to avoid bombing and strafing within friendly lines was largely overcome by the adoption of a bomb line. Beyond this line (one predetermined for the 6 hours immediately after H-hour, another for the remainder of D-day, and thereafter subject to daily changes as decided by air and ground staffs) ground forces ventured at their peril and targets could be attacked at will. Behind this line no bombing or strafing was to be conducted without specific arrangement with the ground forces, and the originator of such a request was to assume the responsibility for clearing the region around the targets chosen for attack.
Ground force requirements
Certain adjustments in the bombing desired by Army planners were necessary to conform to bomber capabilities. When requests for destruction of fixed defenses, explosion of mine fields, cutting of underground cables, elimination of barbed-wire entanglements or antitank obstacles, demoralization of front-line troops, delay and disruption of reserve elements, and the blocking of transport by bombing French towns-when such requests were submitted by Army commanders it was necessary to point out the probable degree of success against each type of objective and then to secure priority ratings so that the bomber strength could be apportioned as desired by the ground forces.
In many instances the destructive effect necessary could be obtained only by use of heavy bombs with delayed fuzings, which would cause the cratering the Army wished to avoid. The probability was emphasized that direct hits on gun emplacements would not be in excess of 2 percent of the tonnage dropped and that in most instances little damage would result. Nevertheless, the Army requested that the attempt be made to destroy those on the flanks of the beaches, believing that some emplaced positions could be put out of action, at least temporarily, and that craters in this area would afford valuable protection to assault troops sent to capture these strong points. Otherwise it was agreed that the air cooperation should aim primarily at the demoralization of front-line troops, with a possible bonus in the destruction of barbed wire and other hazards. No request was made for the elimination of underwater mines or obstacles. The Army commanders were informed of the possibility of gross errors causing casualties among troops in assault craft and accepted them as a necessary risk.
Selection of targets
Certain categories of requested targets were not deemed by Eighth Air Force to be satisfactory for heavy-bomber attack. In three instances the matter was submitted to SHAEF for determination. The first concerned marshalling yards in occupied territory, and objection was based on the belief that medium bombers would be adequate, that the damage could be readily repaired and hence would not justify the effort expended, and that the proximity to built-up areas would result in civilian casualties and property damage out-weighing the disruption of enemy communications. The second case involved the bombing of bridges. It was considered that the nature of these targets would require a very great expenditure of effort in relation to probable damage achieved and the erection of temporary spans could largely nullify successes gained. In the third instance the matter concerned choke-points in French towns which the 21st Army Group desired to have blocked by rubble in order to delay enemy reinforcements. The stand of the Eighth Air Force was based on the risks to civilian lives and property. In all three cases SHAEF, motivated by military expediency, directed that the attacks be made. Arrangements were made to drop warning leaflets sufficiently in advance of the last-mentioned type of attack to enable the civilians to evacuate the threatened areas.
