Index

• 1. Interdiction How Air Can Perform the Enormous Task of Isolating a Battlefield
  
• 2. How Interdiction Worked in Winning the Battle of France
  
• 3. Seine River Interdiction Line
  
• 4. German Tanks, M/T were Cut To Pieces
  
• 5. Belfort Yard Battered
  

INTERDICTION
How Air Can Perform the Enormous Task of Isolating a Battlefield

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Allied invasion plans were based on the theory that, once the Luftwaffe's back had been broken, a heavily defended coast could be breached by isolating the projected landing area through air attack directed against the enemy transportation facilities servicing that area. How this works, even when the troops and fortifications in the area are maintained by a rail network as formidable as that in northern France, is shown in the diagram above.

First step is to saturate rail yards, lowering operating efficiancy and forcing the diversion of men and equipment to keep the system open for military traffic.

Second, a line of interdiction is set up by cutting all rail bridges across a natural barrier such as a river. This further hampers the flow of supplies by forcing the enemy to stop his trains at the river, unload into trucks or boats, and then load into different trains on the opposite side.

Third, another line of interdiction is established, forcing a double train-to-truck-to-train transfer, and creating a zone from which the locomotives and cars inside cannot escape, nor those outside get in.

Fourth, the irreplaceable rolling stock isolated in the zone of interdiction is clogged at certain points by bombardment, and then depleted by fighter attacks until the enemy is driven to road transport. This is undesirable from his point of view because trucks are less efficient than trains, because they are more vulnerable to strafing attack, but mostly because of the shortage of trucks, tires, and gas created by strategic bombing.

Fifth, the fighter attack shifts to the roads, forcing the enemy to operate only at night, in widely dispersed motor convoys, under rigid blackout conditions, all of which reduces the flow of supplies to the coast still further.

Sixth, a landing having been made, consolidated, and ground strength built up faster than the enemy's, all with the help of the transportation snarls described above, a series of end runs is undertaken to flank the enemy and annihilate him. To see how this actually worked in France, turn the page.

HERE IS HOW INTERDICTION WORKED IN WINNING THE BATTLE OF FRANCE

As in the theoretical example on the previous page, the invasion of France posed to Allied planners the problem of landing on a coast bristling with fortifications, and strongly garrisoned with troops which could rapidly be concentrated at any point through use of the densest rail system in the world.

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Phase One (D minus 90 to D-Day). Air's first task was to prevent the movement of German troops from the Calais coast to Normandy as the invasion developed. The map above shows how the campaign began with bombardment of all the rail centers servicing these areas. This achieved the double purpose of improving our chances of securing a foothold without betraying where the attempt would be made. Next a line of interdiction was established between Paris and the sea by cutting bridges across the Seine river. Another such line was then set up along the Albert Canal and Meuse river. Purpose of this was to create a zone of interdiction between the two, and, by a further concentration of attacks within the zone, to heighten the impression that our landing would be made there. A glance at the map will show that the stage was now set. The bulk of the German forces was bottled between two lines of interdiction (shaded area around swastika) which at the same time cut off the real landing area from all directions except the south.

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Phase Two (D-Day to D plus 55). Under heavy air cover landings were made, consolidated, and the Cherbourg peninsula captured in due course. However, a ring of enemy troops was thrown around our perimeter, successfully containing it for a period of weeks. The next job therefore was to build up sufficient force to break out, preventing at the same time a similar buildup by the enemy. Accordingly, another interdiction line was established along the Loire river, linking up with the Seine line west of Paris and completely sealing off the battle area. A fourth line was set up east of Paris, extending (dotted red line) to the Loire line at Orleans. Meanwhile, a heavy war of attrition was being waged on the perimeter. We could afford it. Germany could not, as she had by now abandoned all attempts to move by rail, and her efforts at resupply and reinforcement by road (dark arrows) were subjected to devastating fighter and bomber attacks. Finally on 25 July a superior Allied force broke through the east end of the perimeter on the heels of a heavy aerial barrage.

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Phase Three (D-plus-55 on). Once through the German ring, Allied armor poured into the vacuum behind it, forming a pocket at Falaise which was largely annihilated by air and ground attack. (Brittany, where a strong FFI movement aided by parachuting agents secured our flank, could largely be ignored.) No enemy stand was made at the Seine, the dangers of a second pocket being too apparent. Instead, the enemy retreated across it in good order despite a terrific jam-up and heavy losses on the banks of the river, whose bridges were still down (see picture on next page). Meanwhile the situation was further exploited by the brilliant and incredibly energetic flanking operations of our tank commanders, who were able to proceed day and night at top speed, aided by air cover and air supply ,(large red arrows), over roads less damaged than those being used by the enemy. A parallel advance by British and Canadian armies nearer the coast completed the undermining of the whole German defensive system in Northern France. Leaving garrisons at the principal ports, the Wehrmacht pulled out, shedding men and equipment at every step.

SEINE RIVER INTERDICTION LINE

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Just north of Paris at Conflans is situated the first of seven rail bridges which cross the Seine river, linking Brittany and Normandy with the great industrial areas of Eastern France, Belgium and the Ruhr valley. Attempts to establish a line of interdiction here were begun in May by the U. S. Ninth Air Force and the British Second Tactical Air Force. By 12 June each of these bridges was down, as shown by the pictures on the opposite page, also each of the thirteen road bridges which cross the Seine between Conflans and the sea. This formidable barrier not only enormously increased the difficulty of transporting German troops and equipment into the invasion area, but it also made it almost impossible for those who escaped the Falaise pocket to get back without enduring withering attacks from the air while packed against the river bank and waiting to be taken across in boats.

Aircraft operating against the Seine bridges were almost entirely B-25s, B-26s, A-20s, P-47s and Typhoons, eugaging in precision bombing, dive bombing and minimum-altitude attacks. Credit was shared about equally bctween bombers and fighters. An operational analysis found that dive bombing was about one-third as effective as minimum-altitude attack, but considerably less dangerous. For the latter to be successful, the bridge had to offer soft abutments, wooden scaffolding, or some other structure in which the bomb could stick while it exploded. Correct fusing is vital in all bridge attacks.

GERMAN TANKS, M/T WERE CUT TO PIECES

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Once the battle for the Normandy beaches was oyer and the galloping epidemic of Allied ground strength had begun to spread east and south, exploiting the enemy weaknesses created by the interdiction campaign, it became the mission of these armies to surround and destroy German military power in northern France before it could escape and reorganize itself. Occupation of further territory had become a secondary consideration. These pictures give a clue to what happened to the German 7th Army after it had been enclosed in the Falaise pocket. Hemmed in from the north by British and Canadians approaching Falaise, and from the south by Americans approaching Argentan, its only avenue of escape lay in the 13-mile gap between these towns. Interdiction, as shown on the preceding pages, had already paid enormous dividends in helping to set up this trap. The final task of air was to help kill the animal inside.

This was done by the closest kind of coordination between ground and air. Constant patrols provided reconnaissance for our ground commanders, allowing them to bring up superior force against any reported enemy concentrations. These were then dive bombed and strafed, and Allied armor, still in communication with the fighter planes, would move in for the kill. As the pocket became smaller and smaller, the congestion within became more acute, and Allied fighters worked the area over with increasing effectiveness. By 20 August, when all resistance collapsed, the entire pocket was carpeted with blasted guns, tanks and trucks.

The size of our air effort is shown by the 11,886 AEAF sorties flown on 18-20 August. German air activity during this period was microscopic. Allied vehicles could jam the roads by day with impunity, as the picture at the right (talken near Valognes on 24 August) graphically illustrates.

BELFORT YARD BATTERED

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One of the great natural barriers of Europe is the chain of the Vosges and Jura mountains which separates central France from southern Germany. Only passage through it is the Belfort Gap, where there is a confluence of rail lines and highways. Thus, the Belfort rail yard is an example of a perfect rail interdiction target. The Eighth Air Force hit it on 11 and 25 May, 17 July and 11 August. Two stages of the last attack, during which 76 heavies dropped 187 tons visually from 19,500 feet, are shown above and below. Cumulative results, right, show locomotive shops almost totally destroyed, transshipment sheed and station shattered, all through lines cut.

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