Overture to Overlord

When Eisenhower assumed control of the Allied air forces in April 1944, he had to decide how best to use those forces to invade Europe. He weighed two major proposals. Spaatz advocated the destruction of Ger- man oil refineries by heavy bombers to immobilize the German armed forces. Opponents of Spaatz's "oil plan" argued that the desired results would not happen soon enough to affect the invasion. Air Chief Marshal Arthur Tedder of Britain proposed the destruction of the German/French marshaling yards and other transportation targets to isolate German armies in the invasion area. Opponents of Tedder's "transportation plan" argued that it did not make effective use of the heavy bombers and, worse, would kill or wound many French civilians. After consulting with Maj. Gen. Pierre Joseph Koenig, commander of French Forces in the United Kingdom, Eisenhower ordered the transportation plan implemented. To minimize civilian casualties, the Allies banned attacks on moving trains and restricted their initial efforts to marshaling yards and bridges. Although Eisenhower insisted on the primacy of transportation targets, he did permit the Eighth Air Force to attack the German oil industry as circumstances permitted.

As a result of Eisenhower's choice, the Ninth Air Force escalated at- tacks against rail centers in the first half of April 1944. On an April 8 mission to Hasselt, Belgium, 163 B-26s dropped 263 tons of bombs and 101 P-47s carried out dive-bombing attacks. Two days later, when P-51s went to dive-bomb the area, the smoke was still rising from the damaged repair shops. By the middle of the month, the Ninth had developed a very effective method for attacking these targets. On a typical mission, four or five groups of B-26s, consisting of about thirty-five aircraft each, bombed a particular rail center. Instead of having large formations drop bombs on a signal from the lead aircraft, attacking forces split into numerous four- or six-cell elements and dropped their bombs as smaller units, thereby increasing accuracy and reducing civilian casualties.

Meanwhile, the Eighth Air Force attacked marshaling yards and other targets in Belgium, northeastern France, and western Germany. The Fifteenth Air Force, operating from bases in Italy, attacked tar- gets in southern France and central Ger- many. By the end of April, the Allied air forces had done enormous damage to many continental rail centers. The Germans responded by intensifying repair work and increasing their antiaircraft defenses around critical areas. In May, the Allied attacks expanded, but the Germans were still able to move trains. 

On May 20, responding to this continued movement, the commander of the Allied Expeditionary Expeditionary Air Force, Air Chief Marshal Trafford Leigh-Mallory of Britain, authorized widescale fighter seeps against moving trains.  Prior to this order, Allied fighters had been attacking moving trains without the express approval of higher headquarters. After May 20, the at- tacks were carried out openly on a large scale. In the next two weeks, fighters damaged approximately 475 locomotives and cut railway lines at more than lOO different points. These raids severely disrupted enemy traffic, ruined equipment, and produced important psychological effects among railroad personnel. French crews abandoned their trains in large numbers, especially after Allied fighters began dropping belly fuel tanks and setting trains on fire by strafing. The Germans reacted by manning the trains with their own crews, but that was not enough. By the end of May, the enemy had been forced to sharply curtail daylight railway operations, even where the lines remained unbroken.

A highly successful interdiction campaign against bridges marked another key phase of the transportation program. After careful examination, Spaatz and Brereton pressed for the removal of bridges leading toward or into the invasion area. After consulting a British railway expert, Leigh- Mallory decided that using fighters to destroy bridges would be a waste of effort. However, on May 9, evidently on Brereton's initiative, eight P-47s dropped two 1,000-pound bombs each on abridge over the Seine near Vernon and demolished it. That same day, the Allies damaged bridges at Oissel, Orival, and Mantes-Gassicourt. Faced with this evidence, Leigh- Mallory decided that tactical forces could do the job and ordered his

airmen to bomb the bridges over the Albert Canal and the Meuse River. On May 24, the Allies made the bridges over the Seine the first priority. B-26s and P-47s began an intense campaign of low-level attacks, striking Le Manoir and Poissy on the 26th, and Juvisy, Le Manoir, Maisons- Lafitte, and Le Mesnil Ande on the 28th. The combination of the bombers dropping 2,000-pound bombs and the fighters diving with 500-pound bombs proved devastating. The Seine bridges fell rapidly, and, despite enormous efforts, the Germans could not keep up with the repairs. As the Operation Overlord invasion date approached, all of the crossings south of Paris were impassable.

Closely associated with the transportation campaign was the neutralization of airfields in western Europe from which the Germans might attack the Allied invaders. At a minimum, the Allies wanted to drive the enemy fighters to bases in the east where they could not threaten the invading forces. By the spring of 1944, the Allies had achieved this goal. However, because the airfields still existed and could be used by a redeployed Luftwaffe, the Allies decided to attack the potential airfields before the invasion. The problem was how to conceal their interest in these installations while inflicting severe damage so close to the invasion date that there would not be time for the Germans to repair them.

Early in May, Leigh-Mallory had identified all usable landing grounds within 350 miles of Caen, France. Assigning responsibility for their neutralization to RAF Bomber Command and the Eighth, Fifteenth, and Ninth Air Forces, he permitted each commander to decide when and how to bomb the airfields. On May 11, the Allies began an unrelenting campaign. By D-Day, June 6, they had attained their main purpose. The Luftwaffe did not have enough usable airfields within practical striking distance of the Normandy beachhead. German air opposition to the invasion was so slight that it astonished the Allied air commanders.

As the invasion date neared. the Allies turned their attention to the enemy coastal batteries. Initially they used medium and light bombers and fighter-bombers against the German defenses, but later they sent the heavy bombers from the RAF Bomber Command and the Eighth Air Force. To conceal their interest in Normandy, they bombed two targets outside the invasion area for every target within.

A German radar net extending from Norway to the Spanish border with France posed another problem for the Allies. This radar could detect airborne and seaborne forces and, if used properly, could coordinate both coastal and flak defenses. Consequently, using the precedent set for the coastal batteries, the Allies attacked two radar sites outside the invasion area for each site within. By D-Day, the Allies had crippled or wiped out nearly all of the sites in the invasion area. As a result, the Germans were virtually blind to Allied movements and thoroughly confused about the nature and intentions of the invasion forces.