Air Power in the Invasion

By Brig Gen Henry J Reilly, ORC *
* the views expressed here are those of General Reilly and not necessarily those of Flying.

Aviation has made the invasion possible and its proper use can be the decisive factor, asserts General Reilly.

The establishment of a second front by the invasion of Western Europe has been decided upon.

The use of aviation will be the decisive factor. It lies within the power of our aviation to determine whether the invasion will be a success with moderate losses, a success with very heavy losses, or even, perhaps, a failure.

The invasion will entail enormous difficulties. It will involve the most difficult fighting under adverse conditions against very strong defenses. It must not fail or bog down in trench lines after bloody losses. But unless we change our present concepts of air tactics and aviation support of ground troops the danger exists that we shall not only suffer enormous casualties but perhaps a serious defeat.

Picture what our troops will have to face wherever they invade Europe:

The success of our Marines at Tarawa will not be too close a parallel. Tarawa was an island, not very long to right and left and not very far from the front beach to the rear beach. Our invading troops on the continent will have to face a position many times as wide from right to left and many times as deep from front to rear as at Tarawa.

The proper use of aviation is the decisive weapon to turn the tables against such opposition. Why is this so?

Dieppe and Tarawa, in general, both show that we are confronted with the same problem of breaking through a strong line of fortifications which caused such heavy losses to the Allies in the last war. This writer saw the "race to the sea" in the fall of 1914. When it was over, the Allied left flank and the German right flank were resting on the British Channel. This established a stalemate from that channel along a fortified line to Switzerland. From then on, until assaults made at the end of September, 1918, all efforts of both the Allies and the Germans to break completely through this line failed.

And why did they fail?

First, because the 1914-1918 situation compelled frontal attacks because flank attacks were impracticable. The right flank resting on the sea could not be turned without an invasion of Belgium from the sea. The Swiss flank could only be turned by the violation of Swiss neutrality which the Swiss would have resisted and which the Germans would have helped them to resist.

Second, an invasion from the sea was a virtual impossibility under the war conditions of that time. The attack on the Dardanelles and various shellings and raids on the Belgian Coast had proved that coast fortifications at that time could keep navy vessels well off shore.

Third, with the rigid fortified line and no flanks to be turned, a strategical surprise was impossible because, once emplaced, the artillery and ammunition needed for an attack could not be moved quickly to another part of the line. It took many days and usually several weeks to emplace all the guns and ammunition necessary for a big attack. In olden days, armies were small enough and compact enough to be maneuvered rapidly and handled in such a way as to outflank the enemy or hit him suddenly at an unexpected spot. With the huge mass armies of modern times, however, such surprises became impossible. It was impossible to conceal the months of preparations necessary for a major battle.

Fourth, the heavy artillery attacks of the war of 1914-18 — notably in the battle of Verdun — finally failed because of

  1. the tremendous expenditure of ammunition and
  2. the necessity to keep the artillery moving forward.
The tremendous effort necessary was possible for the lighter guns only. At Verdun, the Germans over a period of months slowly crushed the French resistance — principally by the brutality of their artillery fire. They finally failed because of the impossibility of maintaining such fire. The law of diminishing returns operated until the German attacks, so successful in the beginning, finally petered out. The same was true of the British attack with a certain amount of French help on the Somme. As at Verdun, the law of diminishing returns brought the attack to a halt without a decisive break-through.

These four conditions which limited operations during World War I have all been changed by aviation.

First, the strategical possibilities of aviation today enable a far-reaching strategy by which the German right flank could be turned by the seizure of Norway and perhaps Denmark. (Early in 1940, the chairman of the aviation committee of the French Senate invited Paul Reynaud, then Minister of Finance, to dinner at his house to listen to the author's arguments in favor of this strategy.) The German left flank could be turned by the seizure of the French southern coast.

Second, aviation today can give warships the support necessary to enable them to engage shore batteries with success for the first time in many decades. Nelson's entry of Copenhagen Harbor under fire and Farragut's entrance into Mobile Harbor under fire, where he said "Damn the torpedoes, full speed ahead," had become merely history which no 1914-18 admiral could hope to duplicate. The landings in Sicily and Italy in this war were made where there were no serious coast defenses. It is doubtful if our warships could have come close enough to Tarawa to support the landing of the Marines had it not been for our Naval aviation.

Third, aviation is so flexible that it introduces once again the elements of surprise and maneuver into modern warfare. It is perfectly possible, for example, to make the air concentrations necessary to indicate a coming attack, say in Norway and Denmark, and shortly thereafter give the same indications of a coming attack on the southern coast of France and then switch to a real attack across the British Channel and North Sea or the Bay of Biscay coastline of France from Brest to the Pyrenees. In other words, if the fullest advantage is taken of the strategical and tactical possibilities of aviation today, we are in a position to overcome the disadvantages which led to failure after failure on the part of both sides to break completely through the enemy's position and obtain decisive victory in the last war.

Fourth, by its power to fly directly over a target, aviation has greatly increased the firepower possible in an attack. Its flexibility is enormously greater than that of artillery because of its ability to start from widely scattered aviation fields or bases. Its long range gives it a power to put concentrated fire on targets on a scale impossible for artillery limited by short range. Had the power of modern aviation been in existence at the time of each of these battles, its tremendous firepower concentrated to back up the German artillery and infantry at Verdun would undoubtedly have been sufficient to give the Germans a decisive victory. This would have ended the war in Germany's favor at Verdun. Similarly, the British and French would have won a decisive victory on the Somme.

How, then, must aviation be used properly to support the invasion?

First, it must use the elements of surprise, by hitting at unexpected places, by making feints, and by using the power of maneuver and surprise. Why have this power of surprise without using it?

Second, it must be used tactically as preparatory fire to break down the enemy's defense works so far as possible before any attack starts at all. This does not hamper the element of surprise because aviation firepower can be switched from target to target. The enemy need not know where the attack will come. Our aviation ought to go after all the fortified coasts for months. Most people who have not seen war at first hand have no concept of what modern fortifications will stand.

Third, after the tremendous battering of the invasion coasts, aviation must assist in covering the landing troops and the advancing troops with fire on every single one of the defensive works ahead oi the infantry and tanks.

Fourth, and most important, is that wherever the invading troops are trying to go forward there must be an accompanying fire, not more than 200 yards ahead of them to keep the enemy in their defenses and fox holes. Under no circumstances must the enemy be permitted to separate the attacking troops and the barrage, or the barrage be permitted to get too far ahead so that the defenders have time to come up after it has passed and turn a murderous fire on the attacking troops. This bombing barrage must be conducted by airplanes closely coordinating their attacks with the ground. troops below. It is not merely a question of the tonnage of bombs dropped by the attacking planes but of directing that tonnage to specific defending targets.

The use of air to support our invading troops in the exact manner prescribed in the above paragraph is vital to the success of the operation. Here are some of the contributing reasons:

Naval guns will be the only artillery other than airplanes available for the initial landing. Tarawa showed the difficulty of getting adequate support from naval guns. These guns are designed to have a flat trajectory — the shell goes straight to the target. While this is essential to fight other ships or airplanes, it too often results in the shell only hitting the top of land fortifications and ricocheting off to explode more or less harmlessly in the rear. Land artillery, on the other hand, except anti-tank and antiaircraft, is designed so that the trajectory is curved. In this case the shell, instead of going straight, goes up into the air and then curves downward to fall on top of the target.

In the Japanese siege of Port Arthur n 1904-05, for example, the Japanese had to send back to Japan and cut their heavy 11-inch coast defense mortars out of their permanent concrete emplacements because their naval guns could not reduce the Russian fortifications and their siege guns did not have heavy enough projectiles. When the mortars opened fire the fortifications began to crumble. Hence, bomber attack must be made on fortifications and ground troops instead of being confined largely to factories, railways, roads, ammunition and supply dumps in the rear of the battlefield.

In a successful attack there must not only be the preparatory fire on the enemy to soften him up before the attack but there must be an accompanying fire throughout the attack. The accompanying fire catches the enemy's defenders when they come out to man their weapons from the bomb-proof shelters where they have hidden while the preparatory fire was going on.

Apparently at Tarawa, one of the difficulties in providing an accompanying fire was because the flat trajectory of the naval guns on the warships could not always be used to furnish accompanying fire to our Marine infantry because of the danger of hitting them. Had we had ships with howitzers and mortars, their high angle of fire well over the Marines and dropping down on the Japanese a short distance ahead of the Marines would have greatly decreased our casualties. (In the Civil War of 1861-65, we had mortar ships. The Austrians used mortar ships on the Danube in 1914-18.)

The accompanying fire is the shield of today's infantry. Just as robbing the man in armor of his shield before the days of firepower left him open to attack, so today the opening of too big a gap between the accompanying fire and the infantry following it leaves the infantry open to attack. In this war the Russians have managed to separate the German infantry following its tanks from these tanks and thus have been able to break up and stop the German attacks.

The fortifications which the Allied troops will find on the invasion coast, and which must be broken through if our invasion is to be a success, are stronger than was the fortified line across Belgium and France from 1914 to 1918 because

  1. we have given the Germans three and one-half years to make their coast defenses permanent fortifications,
  2. the assault must be made from the sea, whereas in the last war the Allies had the greater part of France in which to establish their artillery, airfields and lines of communications, and
  3. the supplies must be landed on the open beach under enemy fire, instead of in protected seaports as during 1914-18.

The French Coast was well fortified against an attack from England for years before the fall of France. There were some fortifications in Belgium and in Holland facing attack from England. Since the fall of these three countries in 1940, the Germans have been busy further fortifying these three countries against an attack from the sea. Of course, for years the fortification of their own North Sea Coast line has been of the most modern type.

The armament of the Maginot Line has been moved to the new coast defenses. The large amount of artillery taken from the Czechs at the time of the seizure of Czechoslovakia has also been put into these defenses except for the Czech field artillery which is in use by the German field ground forces.

Furthermore it should be noted here that, contrary to the belief of most of the public, fed by false propaganda of doubtful origin, it was not the permanent fortifications of the Maginot Line that failed but the lack of any such fortifications along the northern frontier of France. The Maginot Line ran north from the Swiss frontier to just east of the Sedan region. There were no fortifications on the long stretch of frontier from the neighborhood of Sedan to the English Channel. The Germans went through this gap. The Maginot Line fortifications were not attacked and captured. They held out until their garrisons were completely cut off by the German advance in their rear.

We are now probably building artillery powerful enough to break down such fortifications as the Maginot Line, which exist today in many parts of the German coast defenses on the continent.

However, the artillery will have to be landed before it can be used. Beachheads of considerable extent in width and depth must first be captured. Our experience in landing on the beaches of Sicily and Salerno, in both of which the Germans drove us back almost into the water before we succeeded, show that such operations need tremendous support in fire from the fleet and from the air. The difficulties of the former have already been indicated.

The reports coming from Italy to date show that the maximum American air power available has not been concentrated to add to the artillery preparatory fire. Similarly, the concentration of airplanes, once the infantry and tanks have started their advance, has been less than that which could have been made. Such support as has been given apparently has been more concerned with communications in the rear of the battlefield than with the German infantry, tanks, and artillery directly opposing our troops.

Instead of aiding the American artillery with the maximum number of American bombers available by adding shuttle bombers from England to planes already based in Italy, we are using American bomber strength to bomb northern Italy, the Tyrol, Austria and the Balkans.

When the Russians, the Germans or the Japanese have any fighting on the ground or at sea they do not disperse their air strength by bombing cities, industrial plants and communications far removed from this fighting as we do. Instead they concentrate their aviation strength against the enemy's ground troops and warships.

Yet our Air Force regulations grant third priority to the only type of tactical effort which can effectively support our troops when the day of invasion comes — namely, direct aviation support of the ground troops in the zone of battle contact.

The bombing of Germany's cities, industrial plants and communications in the rear undoubtedly is wearing down their strength by attrition just as the brutal attacks by the Allies on the western entrenched front from 1915 to 1918 wore down the armed strength of the Germans.

However, this attrition method did not produce victory for the Allies. On the contrary, it so wore down their own strength that by March, 1918, due to Russia's leaving the war, the Germans for the first time had greater strength on the western front than did the Allies. Only the arrival of American reinforcements at the rate of several hundred thousand a month for several months months gave the Allies supremacy once again.

The bombing of Germany has failed so far to bring any definite signs of weakening the German fighting ability on the Russian or Italian fronts. It has not stampeded the German population. It has not prevented the German submarines from going to sea and returning to their bases.

Nor are the Germans the only ones who are suffering. For us to replace the 829 American bombers lost in operations from Britain alone since January 1, 1943, requires the labor of more than 13,000 workers at 40 hours per week for one year. To launch repeated attacks by 1,000 bombers necessitates the constant presence of approximately 2,500 bombers on the airfields from which the attacks start. In order to replace the losses and planes damaged on the raids, a ratio of two and one-half to one must be maintained. The ground forces needed for the maintenance of the planes, and the personnel required for administration, supply, health, and so forth numbers approximately 125,000 for the 10,000 officers and enlisted men who man the 1,000 bombers. This is costly for us as well as for the Germans.

Napoleon said: "Fire is everything; the rest is nothing." When the invasion is made all possible fire must be concentrated in support of our landings. The decisive share of that power must come from aviation.

Dieppe proved how well-fortified is the western sea coast of Europe. Tarawa proved that, even with naval and air support much more powerful than that of Dieppe and far stronger than that possessed by the enemy, a successful attack upon land fortifications from the sea can be made only at the price of heavy casualties.

The successful invasion of the continent of Europe to set up a second front on a decisive scale must be attempted — not with a few divisions, but probably with 50 to 60.

The British Isles are close enough to allow aviation to be used to support the invasion against a large part of the German western coast defenses. Carrier-based planes, due to the ability of carriers to concentrate off any coast, can add materially to the strength of attacking aviation. If and when we have driven the Germans out of the Valley of the Po, aviation based on that valley and on Corsica will be close enough to the coast defenses of southern France to be used in the same manner.

And now the Teheran conference has decided upon establishment of a second front by the direct invasion of the continent. To be effective, the invasion must be made with sufficient troops to use up Germany's reserves. This offensive, combined with a Russian attack, should bring about Germany's decisive defeat by crushing her ground forces and thus securing her airfields and submarine bases. Such an accomplishment is necessary if unconditional surrender is to be had.

The decisions made indicate that the Teheran conference was convinced that aviation bombing alone could not bring about the unconditional surrender of Germany. In other words, victory will come not through Douhet's theory that air power can bring victory through bombing the enemy's industry and communications, but through Napoleon' s which contends that it can only come through crushing the enemy's armed forces.

If the invasion is to be successful — without outrageous losses and within a minimum of time — it must be made with the strongest naval concentration, with 50 to 60 divisions, and above all with the fullest strategical and tactical powers of aviation directed wholly to the support of the armed forces, both land and sea, making that invasion.

This article was originally published in the March, 1944, issue of Flying magazine, vol 34, no 3, pp 21-23, 146, 150.
The PDF of this article includes photos of B-17s at altitude and a map, "Europe's Invasion Coasts and Allied Air Bases" showing areas of US air bases and German fortification zones.
Photos credited to AAF; map by Hal Morris.