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U.S. Bombing Survey, WW I (summary)
Scanned and edited by Air War College, Nonresident Studies

AWC Note: It was simply styled: "U. S. Bombing Survey," and was composed of 66 separate reports -- each on a separate target or group of closely related, geographically proximate, target towns and aerodromes -- followed by this 8-page "Narrative Summary," which includes casualties inflicted, dollar amounts of damage (actually in Marks), and in each report the factories or specific targets are always indicated. Actual targets were surveyed by twelve teams -- each consisting of one officer, a photographer, and a chauffeur. The principal investigators were Air Intelligence Section officers Capt Emery A. Greunke and 1st Lt. L. J. LeTourneau.

Narrative Summary

Material Damage

The material damage, as recorded in 66 of the 140 cities, amounted to 35,449,190 marks but this should not be taken as all of the damage done in the 66 cities because in some cases records had been kept of only a part of the damage. For example, the damage done in Boulay includes only that done to the city and to the gasoline depot, while aerial photographs show that considerable damage was done to the airdrome which was one of the most important German airdromes on that front. A fair opinion may be formed of the damage done in cities where it was impossible to obtain an estimate in money by reading the detailed reports on Longuyon and Hagondange because the records in these two cities did show the kind of damage done in each raid.

Then, there are cities such as Karlsruhe, Freibourg, Offenburg, Stuttgart, and Mannheim on the eastern side of the Rhine which could not be covered because the German authorities refused to give the American officers permission to enter them. One of the American officers was taken to Karlsruhe by a French officer to obtain permission from the German authorities to carry the investigation into that city, and although permission was refused, succeeded in seeing the city mayor who stated that 164 people had been killed and 326 wounded by bombs.

Cost of Protection

The cost of protection as recorded in 36 cities amounted to 9,141,049 marks, which includes the expense of railroads, cities, and industrial concerns. To this should be added the amounts expended by individuals, by the military authorities, and the amounts that will be spent in tearing down shelters and other protection for which there will be no further use. Many individuals walled in their windows and built small shelters in their basements and small retail stores furnished some protection for their employees. The military authorities probably expended the largest amount of money for protection. Almost every city of any importance was protected by anti-aircraft artillery, and some were protected by balloon barrages and home defence flights. The Germans had 11 home defence flights of 10 machines each along the Rhine Valley prior to June 1, 1918, and during the first part of June increased the number of flights to 17 and the strength of a flight to 14 machines. The original cost plus the expense of maintaining these air units amounted to 53,000,000 marks at least. The military authorities also maintained a barrage of 63 balloons at Cologne, one of 39 at Esch, one of about 45 at Hayange and Knutange, and one of about 100 in the Saar Valley. The original cost plus the expense of maintaining these barrages amounted to 23,425,480 marks at least.

In addition to the balloon barrages and the home defence flights, the military authorities furnished anti-aircraft artillery, machine guns, and searchlights for almost every city of any importance. Coblenz, a city which was not important from an industrial standpoint, was protected by 12 anti-aircraft guns of 7.5 cm and 9.0 cm calibre, and 18 machine guns with a total personnel of 2 officers and 200 men. An attempt was made to obtain the approximate number of anti-aircraft guns used to defend cities in the interior but it was found that the information was unreliable and resulted in duplications wherever the guns protected more than one city.

The cost of protection against air raids was not limited to those cities actually bombed. Troisdorf and Hoechst were never bombed but 174,000 marks were expended for protection in the former and 435,145 marks in the latter. Undoubtedly every city of any importance in the Saar, Rhine, and Moselle Valleys made some expenditure for protection.


As a general rule bonuses were not paid as a means of getting the employees to work during a raid or alert or in factories which were frequently bombed. The general opinion of the employers in the factory was that during a raid or an alert they would be held responsible for the casualties while if the employees went to the shelters the employers would be relieved of responsibility. Consequently, in most cases the employees sought shelter as soon as the alert was sounded and no deduction was made from their pay for the time lost. In a few cases four or five men were paid a bonus to remain at work during the alert to carry on the necessary work. Out of a total of 80 cities, 60 were found in which no bonuses were paid, 10 in which bonuses were paid which amounted to 4,213,371 marks, and 10 in which the information was not available.

Loss of Production

Out of 80 cities, 20 were found where the information on the loss of production was not available, 22 in which there had been a loss of production which amounted to 71,563,723 marks, and 38 in which there had been no loss of production. This by no means covers the entire loss of production in the area investigated. Hoechst and Troisdorf were not bombed but there was a loss of production, 5,848,173 marks in the former and 974,800 marks in the latter. The loss of 71,563,723 marks includes only the loss in 20 cities which were bombed and 2 which were not. All cities in the vicinity of those raided sounded the alert and production stopped. The 38 cities in which there was no loss of production were usually railway centers, depots, airdromes, or cities in which there were no factories. With a very few exceptions every factory manager admitted that there had been a loss of production and the manager of the Burback-Esch-Dudelange Iron Works at Esch stated that it took about 30 minutes after a raid or alert before the entire personnel was at work.

While the loss of production is not an entire loss, the raw material appears to be the only part that was saved.

Extra Expenses

In addition to the above listed damages there were a few expenses incurred which could not be placed under those headings which amounted to 7,956,751 marks.

Killed and Wounded

The information available shows that 641 people were killed and 1262 wounded in 22 cities. While the number of killed and wounded may not be considered very important, inasmuch as most of these were civilians, it did have a direct effect on the morale of the people and may have entailed an additional expense to the government. In Ludwigshafen a total of 1,607,000 marks was paid to the 53 wounded and to the dependents of the 33 killed. This was the only case found where such an expenditure was made and it is doubtful whether it was made in other cities but if this same principle had been applied in other cities an expenditure of approximately 35,000,000 marks would have been necessary.

Raids, Alerts, and Working Hours Lost

In 15 cities where the information on the number of alerts, raids, and working hours lost was available, it was found that 220 raids and 1647 alerts resulted in a loss of 2187 working hours or a loss of one hour and ten minutes for each raid and alert.

In 20 cities, where the number of raids and alerts were known there were 291 raids and 2447 alerts for every raid. Troisdorf and Hoechst were never raided but the former had 25 alerts and the latter 98.

The system of alerts varied in different parts of Germany. In the Saar Valley all industries controlled by the government were notified as soon as the bombing planes crossed the lines and again when it appeared likely that some city in the area would be raided. In some cases the alerts were sounded along the entire route which airplanes usually took in reaching certain objectives that an alert has been sounded in Cologne when Ludwigshafen was raided, simply because the airplanes had previously taken that route to Cologne. In other cases the alert was sounded over a certain area such as the Thionville area when it was known that the airplanes were proceeding in that direction. However, the system of alerts was undergoing a change during the last part of the war which would have reduced the number of alerts and the number of working hours lost because of alerts. A system was used in the vicinity of Kaiserslautern through which a city never sounded the alert until it was known that the airplanes had passed over the nearest large city between there and the front line. This system would probably have been used more extensively had the war continued and would have resulted in a smaller number of alerts and a smaller number of working hours lost because of alerts.

Moral Effect

It is certain that air raids had a tremendous effect on the morale of the entire people. Americans who had been in this area during the war claimed that an alert always resulted in confusion and factory managers admitted that the morale of their employees had been affected, the manager of the Burback-EschDudelange Iron Works in Esch claiming that it took 30 minutes after an alert to get everyone at work. In the raid of August 23, 1918, on Ehrange, three people died of fright. Prominent citizens in Treves held a meeting at which it was suggested that all bombing be stopped. Railroad officials at Thionville claimed that it was necessary to increase the number of workmen around the station because the morale of the workmen had been lowered by bombing making them unable to perform the work which they were expected to perform. Boulay had the reputation of being a poor rest area for troops because it was bombed frequently and because about 50 soldiers had been killed during one raid.

Judging by the information received, night bombing appears to have had the greatest moral effect, probably because the largest percentage of people lost sleep because of night raids and because they would not see the airplanes which were dropping the bombs while, in the event of a day raid, they merely stayed in a shelter instead of in the home or factory and knew just where the planes were.

In addition to the above named damages done by bombing, there are some effects which cannot be expressed in terms of money. Among these the delay of railroad traffic is probably the most important. In Luxembourg the average time which one or more tracks were out of commission in eight raids was 12 hours. It is impossible to state just how much inconvenience to the German Army resulted from these delays and the many others that occurred in other railroad yards because this depended entirely upon the nature of the traffic passing through at that time and whether a main track or a switch track was hit.

While an estimate of the loss of production has been given in money, this shows only the selling price of the articles and not what the buyers would have paid for the products had it been possible to manufacture them. Most of the factories were running 24 hours a day and a loss in production meant that the loss could not be made up by working over time. Most of the iron and steel turned out was used in the manufacture of war material. The question comes up as to just how much the government and business concerns would have paid to obtain this extra product. The enormous expense of maintaining balloon barrages, home defence flights, and anti-aircraft artillery must be an indication that the material was needed as well as that the popular clamor for protection was great.

Too much emphasis cannot be given to the importance of hindering the enemy's military organization. The importance of the material damage as shown in this report may be discounted because it includes a large amount of damage done to private property which was of no military importance except insofar as it affected the morale of the people. This also applies to a less extent to the other forms of expenditures made by and the damage done to the enemy's army and its manufacturing and transportation agencies is of direct military importance, the material damage hindering the work of the army and its agencies and the expenditures necessitating an increase in loans which would not have been necessary if the money had not been expended for protection, etc.

It has been shown that the morale of the fighting forces as well as that of the civilian population was affected by bombing, that the employees of organizations controlled by the government were not able to perform their work because of bombing, that the transportation of the enemy's troops and war supplies was hindered by bombing, and that the manufacture of war material was hindered. It would be folly to attempt to estimate these effects of bombing in terms of money, and it appears that questioning whether these effects plus the effects which can be estimated in money justified the expenditures made for bombing is like asking "Did it pay to win the war?"


The following points should be considered:

After having taken the above points into consideration, it appears that the total direct damage of 133,185,841 marks and the loss in production of 71,563,723 marks may be doubled and still keep the estimate of the damage done by bombing below the amount which actually was done, and that the expenditures made by the Allies for bombing were justified.

Criticisms of Bombing in the Present War

The greatest criticism to be brought against aerial bombardment (British—American did not have enough bombing aviation to warrant its employment other than with our ground forces—France did not approve of this use of its bombing aviation) as carried out in the war of 1914-1918 is the lack of a predetermined program carefully calculated to destroy by successive raids those industries most vital in maintaining Germany's fighting forces. The evidence of this, is seen in the wide area over which the bombing took place as well as the failure of crippling, beyond a limited extent, any one factory or industry. (It might be well to add that in many conversations with officers of the British Independent Air Force there was a growing feeling of dissatisfaction against their bombing policy. It was the statement of these officers that they did not believe they were getting the best results possible and that while the wish and later the decision to "bomb something up there" might have appealed to one's sporting blood, it did not work with greatest efficiency against the German fighting machine. It was on the return of an American officer from a three day visit with the British that it was learned of the disgust held by a British bombing expert—who had achieved very good results in bombing submarines—of the inaccuracy of bombing by the British Independent Air Force and the unintelligent choice of targets.)

The criticism is also directed against the bombing of a town rather than some definite objective of military value in the town. This is shown in the bombing of Treves, Ludwigshafen, and several of the steel industry towns where the legitimate targets, which are respectively the railroad, Badische, Anlin and Soda Factory, and steel works, are all easily capable of being hit and the action should have been concentrated on them alone.

This investigation has decidedly shown that the enemy's morale was not sufficiently affected to handicap the enemy's fighting forces in the field. The policy as followed out by the British and French in the present war of bombing a target once or twice and then skipping to another target is erroneous. Greater results would have been achieved by bombing a single target three or four days in succession. By this method the effects of cumulative results are obtained. It may be said, however, that the occasional bombing of a town of general manufacturing importance is productive of good results for it tends to force factories to close every time an alert is sounded....

Bombing for moral effect alone such as took place over Cologne, Frankfort, Bonn, and Wiesbaden, and which was probably the excuse for the wide spread of bombs over a town rather than their concentration on a factory, is not a productive means of bombing. The effect is legitimate and just as considerable when attained indirectly through the bombing of a factory.

The bombing of railroads presents a particular plan of bombardment, which either through lack of machines or disbelief in the theory, which is outlined in the following chapter, was never practiced in the area investigated.

Suggestions for Future Bombing Campaigns

The operations of a bombardment aviation must be an integral part of the mission of the entire air force and consequently of the ground forces and the army as a whole. There can exist no such force as a separate or independent bombing force.

The three kinds of bombing that are of most importance are, first, that directed against war industries; second, that against railroad lines; and third, that against an enemy's troops in the field. In considering the first a careful study should be made of the different kinds of industries and the different factories of each. This study should ascertain how one industry is dependent on another and what the most important factories of each are. A decision should be reached as to just what factories if destroyed would do the greatest damage to the enemy's military organization as a whole. On these factories the entire available bombing force should be concentrated until it is satisfied that the factory is sufficiently crippled. Once the plan of bombardment is chosen it should be held to religiously and a choice of immediate targets affected only by weather conditions and airplanes available. Factories should be bombed night and day successively as far as the weather will permit until the desired results are thought to have been accomplished. However, there is a limit to this, inasmuch as the enemy will concentrate its protective organizations to a prohibitive degree if one target is bombed entirely to the neglect of others.

The bombing of railroads presents a different proposition. The object in view is to hinder troops and supplies from arriving at the front. This is done by not only bombing two or three of the larger yards and stations but at the same time bombing smaller stations through which traffic could be diverted. The instance when all traffic was stopped in Thionville for one week may be well used as an illustration. This traffic was immediately routed via other stations which were not bombed and the good results obtained in Thionville were lost because traffic was probably not held up more than five or six hours.

A map of the entire network of railroads showing single and double track lines should be studied with reference to each sector of the front and with reference to the least number of stations chosen which if successfully bombed would cut railroad communications to the front. Under railroad conditions as existing in northern France and western Germany five to eight stations would usually control about 100 kilometers of the front.

The bombing of railroad stations for the purpose of severing communications to the front should be carried out only immediately preceding and during a major operation, and at this time the entire bombing force should be concentrated on this work, bombing night and day the various stations forming the cordon. Only in this way can results be expected from bombing railroads. The occasional attempt to cut a track is useless as the resulting delay is negligible....

The fact is brought out very forcibly in the reports on the several railroad stations bombed namely, Luxembourg, Thionville, Treves, Ehrange, Metz, Conflans, and Dommary-Baroncourt, that unless the main tracks are cut the delay in traffic is negligible because the obstruction is easily overcome by switching in the yards. It follows then that in order to obtain the greatest delays the main tracks entering or leaving the station must be destroyed. This is not impossible as can be seen from the detailed report on Dommary-Baroncourt.

Night bombing whenever possible has usually been found to be more accurate than day bombing. This statement on the respective value of night and day bombing is based on statements which factory managers and city officials made on this subject.

Concerning the third phase of bombing, viz.: the bombing of troops in the field, the value of this to affect the morale of the fighting forces has been seen and is easily understood in all armies.

Conclusion [not part of original report]

The post-World War I survey served its purpose in that it helped to shape bombing policies and operations of the U.S. Army Air Corps and the U.S. Army Air Forces (USAAF). It indicated, for instance, that the best results from a bombing campaign could be obtained by identifying and destroying critical components of the enemy's industrial complex, a targeting system which previously had been advocated by Gorrell in his plan for strategic bombing and which would be used by the USAAF in the bomber offensive against Germany in World War II. The survey also indicated, to cite but one other example, that more could be accomplished by bombing a definite military objective in a town than by bombing the town itself, this being the policy that would be adopted by American airmen who opted for precision rather than area bombing of Germany in the Second World War.(1)

The link between the bombing survey in 1919 and USAAF bombing policies and operations in the 1940's was the Air Corps Tactical School. The school's library, which contained many World War I documents, including Gorrell's plan for strategic bombing and other important items from "Gorrell's History," had a copy of the narrative summary containing the conclusions, criticisms, and suggestions resulting from the survey.(2) The bombardment manual used as a text at the school during the 1930's cited and quoted the survey.(3) Laurence S. Kuter, Haywood S. Hansell, Jr., Ira C. Eaker, Curtis E. LeMay, Emmett O'Donnell, Jr., and others who would occupy key positions in the USAAF in World War II were thus exposed, and had access, to the survey while attending the Tactical School at Maxwell Field in the 1930's.

Despite citation in the text, notes, and bibliography of the Tactical School's bombardment manual, the survey seems to have escaped the notice of persons writing on the early history of U.S. military aviation and air doctrine.(4) One reason is that the copy of the summary report that was in the library of the Tactical School when the manual was written in 1930 has been "lost." If it has survived, it should be with other documents of the Tactical School in the Albert F. Simpson Historical Research Center at Maxwell Air Force Base. Researchers do not find it, however, in the Center's catalog (at least not under any logical heading), and it has not been located among the Center's documents.(5) Furthermore, the two copies that were incorporated into "Gorrell's History" were added after the basic history had been assembled at Tours in February 1919. Those copies became the last two volumes of the massive 280-volume compilation and, like some other late additions, were not entered into the index. Consequently, there was nothing to call the researcher's attention to the presence of the survey as part of "Gorrell's History," which over the years has been the principal source of documentary information about the Air Service, AEF, in World War I.