Aircraft in Warfare (1916)/Chapter 18

by Frederick William Lanchester

CHAPTER XVIII.

RETROSPECT. FURTHER NOTES ON THE N-SQUARE LAW. PARTIAL CONCENTRATION. AIR RAIDS: VALUE OF NUMBERS. STRATEGIC EMPLOYMENT OF AIR POWER.

§ 114. Scope and Limitations of the Present Work. In the present work it has been the author's endeavour to give an account of the existing position and the future possibilities of aircraft in its Military and Naval usage; in so far at least as present day knowledge permits of a reasoned forecast. There remains considerable ground however, to cover which no attempt has been made; thus we have the whole subject of aeronautical photography in its present relation on which much might have been said; also many quasi-technical questions connected with aeronautical signalling, by wireless and otherwise, might legitimately have been introduced. Beyond this the whole subject of aeroplane design, as affected by the various kinds of usage in warfare, is itself one of vast and intricate interest,—this has been barely touched upon. In these matters considerations of secrecy have necessitated reticence; the author had obviously to steer clear of much that was known to him on the subject of our aeronautical equipment, and to confine himself for his facts to such material as was common property before the date of hostilities, or had become so since. As an indication that the position has not been without difficulty, it may perhaps be mentioned that (contrary to what might be expected) it is not always permissible to reproduce matter which has already been published in the press; should it thus appear that the author has not taken full advantage of material already published elsewhere, it will be fair that he should be credited with an adequate reason. Certain digressions from the main subject have on the other hand been made, and here and there speculative incursions into the unknown have been ventured. The most important digression is without question that constituting the subject matter of Chapters V, and VI., involving the demonstration of the n-square law. The author believes that this law will, in due course, be recognised as fundamental even in relation to ordinary military operations where its application is commonly masked by conditions extraneous to the hypothesis. Still more readily will its importance be recognised in Naval warfare, as already exemplified by the Battle of Trafalgar.^[1] The clearest and cleanest application of the law, however, will unquestionably be in connection with aerial warfare, here the author predicts that, other things being equal, it will be found to operate with almost mathematical precision.

§ 115. The n-square law as affected by the Technique of Gunnery. In the application of the principle of concentration and the n-square law to Naval warfare under modern conditions, a difficulty occurs which has not so far been adequately dealt with, and which is worthy of full discussion. This difficulty mainly concerns existent methods of range finding, and is to the effect that when the fire of more than one vessel is brought to bear on a single ship of the enemy, the same accuracy—as evidenced by the percentage of hits—is not attainable as in ship-to-ship combat.

It is to be understood that after the range has been found as accurately as possible by the, instrument known as a range-finder, the final corrections are made by firing salvos, each salvo being observed, and an appropriate correction given. When the range has been thus determined, firing by salvos may be discontinued and independent firing resorted to, the main advantage of the latter being an increased rapidity of fire. If it be observed that the firing is becoming wild, that is to say, if the range has been lost, firing by salvos may be resumed.

The objection to more than one battleship making a target of a single vessel of the enemy is that it is difficult to avoid uncertainty as to whose projectiles are going wild, and so when independent fire is the order of the day, it is impossible for the gunnery officer to tell whether his own gunners have lost the range or whether the bad shooting is from the co-operating vessel. It then becomes necessary for both ships in turn to resort to salvo firing, in order to check their range and correct their aim, and thus at the best the speed of fire is unavoidably reduced at intervals during an engagement.

The objection no doubt is valid, but, like other objections, the question is one of degree. The loss of speed of fire when salvo firing is adopted depends to a great extent upon the type of vessel, and more especially upon the armament. Thus if the vessel be one of the pre-dreadnought period having in its primary armament guns of various calibre and of different rapidity of fire, it is clear that in salvo firing the lighter guns (also the more rapid) -either will not be employed or will have their speed of fire regulated by that of the guns of heavier calibre. In the case however, of the all-big-gun ship—as dating from the original "Dreadnought"—the loss is not so great, and the objection of proportionately less weight.

It is to be remembered that at modern ranges, sometimes amounting to a distance of 8 or 10 miles between opposed fleets,^[2] the time of flight of the projectiles is very great. It may amount to some 20 or 30 seconds, and thus if two vessels are concentrating their fire on one of the enemy and firing by salvos, it will frequently be the case that two salvos of projectiles are in flight at the same time, and the uninitiated would not be certain which salvo belongs to which vessel: for the professional gunner however, the matter is different. Although the correct range may not be known or may be wrongly determined in the first instance, the gunner, or the officer responsible for the control, knows precisely the range for which he has set his elevation, and consequently he knows to a fraction of a second the interval which will elapse between the discharge of the salvo and the time the projectiles strike the water; thus unless two salvos are actually fired to strike the water within say a second of one another there will be no reasonable doubt which is which.

It may fairly be urged that the troubles of observation and of gun fire direction in naval actions tend to increase, and at the best the conditions are already sufficiently exacting. It is, for instance, not uncommon when combatant vessels are separated by some 8 or 10 miles, for destroyers and torpedo boats to be told off to create clouds of smoke, by which the difficulties of observation may be indefinitely increased. It is probable, in fact it is almost certain, that in the future the aeroplane will come to the rescue of naval gunnery, just as it is already employed in co-operation with long range artillery on land. The author believes that in future naval warfare much of the observation work and fire control will be corrected by aircraft, either dirigible or aeroplane being used; under these conditions it will be necessary for the battleship to notify to its associated aircraft the range of each salvo, so that when the fire of two or more vessels is concentrated on one, the aerial observer will be able to locate the position of any given salvo with certainty. There are many ways in which this might in effect be accomplished; for example, a smoke or flash signal could be fired on board the battleship at a prearranged one or two seconds' interval before the salvo is due to strike the water. The observer or airman will note the said signal and pick out the corresponding salvo from the splashes of independent fire or of salvos from other vessels, signalling in reply whether too short, too long, or right, or left, according to a pre-arranged code.

It will be quite clear from the foregoing discussion that although undoubtedly two or three ships concentrating their fire on one of the enemy may be detrimental to accurate shooting, the difficulties are such as can be met, and that with only a moderate loss of fire efficiency. Now, if the advantage shown to accrue from fire concentration, as exemplified by the n-square law, were something trifling or negligible, in comparison with the difficulties involved, then, without doubt, it might be judged that in practice the ship-to-ship combat would be the best, even when a numerical superiority exists. But the advantage of concentration as exemplified by the n-square law is not negligible or trifling, it is overwhelming, and of such a character as to entirely outweigh any objections which can be raised from the gunnery standpoint.^[3] In brief, the controversy (so far as it is so) is a conflict between a fundamental principle and a matter of technique, and we know that in all cases when such a conflict takes place, it is the technique which has to adapt itself to meet the fundamentally important condition. The technique in the present case is the technique of gunnery and fire control, and the author believes that it cannot be put too strongly that it is "up to" the gunnery officer (whenever possible) to carry into practice the concentration of the larger force on the lesser and to adapt his methods, cost what it may, to meet the requirements of the case; he cannot afford to flout a fundamental principle for the sake of simplifying the technique of his profession.

Fig. 18.

§ 116. The n-square law and Partial Concentration. In § 42 it was shown that if the whole of the "combined" fleet of 46 ships had been concentrated upon the British 40 ships the annihilation of the latter would have been complete, leaving the combined fleet victors with the equivalent of 23 whole ships to the good; this is now represented graphically in Fig. 18. By inadvertence this was referred to (quoting Villeneuve) as "the usage of former days." This is not strictly accurate, at least it requires qualification.

According to the said "usage of former days" 34 of the British vessels would have been opposed to 34 of the enemy ship to ship, and the remaining 6 British would have been opposed to 12 of the enemy, these conditions are represented graphically in Fig. 19. Thus it will be seen that the numerical surplus is reduced to 10.4 ships, the case being one of partial concentration. Of course in actuality the scheme, however carefully planned, would never result in the perfectly well ordered doubling of the excess of one fleet on the rear ships of the other; the construction, however, given in Fig. 19 is quite elastic, and any departure may be readily dealt with. Thus Fig. 19 may be taken as the

Fig. 19.

appropriate general graphic construction for the representation of any case of partial concentration in accordance with the n-square law.

It is worthy of remark that in cases of partial concentration there may always be a second or after phase in the battle when the residue of the superior force concentrated on the "tail" of the enemy having done its work, will throw its weight into the main combat, the final conditions will then be more nearly the same as if the initial concentration had been complete, as assumed in § 42.

§ 117. Air Raids: The Value of Numbers. The importance of numbers in duties other than actual fighting does not, generally speaking, follow the n-square law; it is nevertheless by no means negligible.

The reason here is that the object attacked is, ordinarily speaking, not an actively hostile force. Thus even where, as in the attack on an arsenal or magazine, the position is protected by counter aircraft artillery, it is fair to assume that the latter is mounted at a sufficient distance from the main object of attack not to be endangered unless bombs are wilfully diverted from their objective. Under these conditions a numerically great attacking force of aeroplanes will manifestly possess an advantage in that they will divide the limited fire capacity of the defending batteries and so suffer less individual punishment; we may take it that the actual injury inflicted on the attacking fleet will be constant and independent of its numerical strength. If, by the nature of the attack, the period during which the air fleet is under fire is lessened by a numerical increase, there is a gain to an extent proportional to the reduction of time the defending batteries can be brought to bear.

In any case the gain is clear, as for example if 10 machines can do in a given time 10 times the mischief of one machine, and if this is done at the same average total loss it is done 10 times as economically. In other words, if a given weight of bombs have to be dropped and this be done by 10 separately attacking aeroplanes, the protecting batteries will be able to "get off" a 10 times greater number of shells than if the attack were planned and executed by the 10 machines simultaneously.

It is of some interest to remark that in § 64 (originally published Nov. 6th, 1914) the suggestion is made of an attack by a "few squadrons" of aeroplanes as constituting a reasonably effective concentration; this is an almost exact forecast of the practice as it obtains to-day, since a "Squadron" may be taken as from 16 to 20 machines and in recent air raids it is reported that about 60 or 70 machines have been employed. We may confidently look to a substantial numerical increase in the air raids of the future. The author is inclined to believe that the tendency of the future will be towards machines of not too great size each dropping a comparatively few bombs, possibly no more than one large bomb being carried by each machine. This conclusion arises as a deduction from the fact that when machines are acting in great numbers it will not be possible (neither will it be politic) for any given machine to pass more than once over the object of attack, hence if a large number of bombs be carried they will need to be released almost simultaneously. Under these conditions a single large bomb of equal weight will possess a far greater potential capacity of destruction.

§ 118. Aircraft v. Submarine. Discussing the value of Aircraft as countering submarine activity in Chapter XI., the subject has perhaps been handled too much in detail, and some of the broader considerations have not been given sufficient prominence. It is not to be supposed that it will always be found possible on locating a submarine, to follow it up and immediately effect its destruction, since in the turbid waters of the Channel and parts of the North Sea (especially in rough weather) a submarine, by diving deeply and steering by gyro-compass, could frequently effect its escape. Quite apart from the method of attack it is the author's view that with a sufficiently numerous air reconnaissance, the enemy submarine will be subject to continuous and unremitting pressure to such an extent that, even where it may escape destruction, it will commonly fail in its object. Thus, taking the case of the large submarine having a great radius of action, it is impossible to make a long passage such as an incursion into the Atlantic from the Heligoland Bight round Cape Wrath, without steaming on the surface for a considerable proportion of the distance. Under these conditions, once located by an efficient air scout service, it will be tracked from day to day if need be, and, sooner or later, either by aircraft or destroyer, it will be brought to book. It is not suggested that under no circumstances could a submarine escape, it would, however, only do so by radically altering its course or by some other manoeuvre involving the temporary abandonment of its purpose; ultimately the influence of aircraft on the high seas will be to keep the submarine submerged, under which condition its radius of action is greatly circumscribed. Thus persecuted, it will be reduced to surface running by night, and even then, unless favoured by the elements, will be liable to attack by fast light cruisers or destroyers which will be informed with considerable exactitude as to the whereabouts of their quarry.

Beyond the above, a submarine or submarines tracked by aircraft will have great difficulty in keeping a prearranged rendezvous, and any "neutral" vessel or fishing craft used for fuel supply and revictualling will be far more liable to detection than is at present the case.

The author believes that it is by continuous pressure of this kind, backed up bj'^ direct attack when occasion serves, that submarine activity will eventually be curbed. It has already been pointed out that the capacity of aircraft to warn merchantmen of danger will alone be sufficient to render the submarine threat quite ineffective, apart from any question of destroying the craft themselves.

Such work as contemplated can only be effectively performed by aircraft if sufficiently numerous, operating in units of flights or squadrons. It will be found comparatively useless to endeavour to carry out the duties in question by single machines, since it will often be necessary to sweep considerable areas of the ocean in order to pick up the trail or get on the track of a submarine that has been temporarily lost. It is thus only when the number of machines and the organisation is sufficiently developed that the power of aircraft as controlling submarine activity will be fully realised.

§ 119. The Strategic Employment of Aircraft on a Large Scale. It is becoming more and more clear as time goes by that the future of Aircraft in Warfare is a subject of such vast potentiality that we may to-day consider ourselves only on the outer fringe of developments destined ultimately to carry us far beyond anything yet conceived. We are at present only on the threshold of a revolution which aircraft will ultimately bring about in the conduct of warfare.

Thus, in the existing phase of the present war, were our aircraft of sufficient numerical strength, it would no longer be a matter of individual and isolated raids on selected places at which the maximum of injury could be inflicted, but rather a continuous and unrelenting attack on each and every point of strategic importance. Depôts of every kind in the rear of the enemy's lines would cease to exist; rolling stock and mechanical transport would be destroyed; no bridge would be allowed to stand for 24 hours; railway junctions would be subject to continuous bombardment, and the lines of railway and roads themselves broken up daily by giant bombs to such an extent as to baffle all attempts to maintain or restore communication.

In this manner a virtually impassable zone would be created in the rear of the enemy's defences, a zone varying, perhaps, from 100 to 200 miles in width. Once this condition has been brought about, the position of the defending force must be considered as precarious; not only will the defence be slowly strangled from the uncertainty and lack of supplies of all kinds, but ultimately retreat will become impossible. The defending force will find itself literally in a state of siege under the worst possible conditions, for the position will be one in the form of an extended line along which the forces of all arms will be definitely immobilised, for the lateral communications will suffer no less than the lines from the rear. Such a position of affairs presents all the elements conducive to complete and irreparable disaster.

Thus, in the extended employment of aircraft, we have the means at hand of compelling a bloodless victory; for, once admit the truth of the present conclusions, the serious and comprehensive threatening of the communications of the enemy by aircraft on the lines indicated can only be answered by his retirement. If he neglects to take this step until too late, he pays the penalty in annihilation or surrender; the matter thus stated becomes one involving the ordinary logic of military necessity. The magnitude of the aeronautical forces and establishment necessary to effect the present purpose must not be under-estimated. In order to prove a decisive factor the devastated zone will need to be of very great area, a belt of from 50 to 100 miles in width probably represents the minimum, and the destruction wrought over the said zone must be complete and thorough in every important respect. The accomplishment, however, is commensurate with the magnitude of the means, for an operation on the scale stated must be met by the enemy by a withdrawal of corresponding magnitude; no ordinary retreat of a few miles to a second line of defence can avail him. From the time his aircraft and air defences are overpowered and his communications placed in jeopardy, he must prepare to fall back on new lines established beyond the zone of devastation, that is to say, if the work is effectively done his retirement can be but little short of 50 or 100 miles. In the present war, this would mean virtually the evacuation and abandonment of the whole of the allied territory at present occupied in Flanders and in the North and West of France. Once the captured territory has been organised and the necessary preparations have been made, the attack would be repeated, and, presuming the continued supremacy of our air fleets, no resistance or defence by the enemy of a permanent character can be sustained.

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1. Chapter VI. §§ 40, 41 and 42.
2. Perhaps even 12 miles as a maximum estimate; so far battle experience is lacking. The 4 or 5 miles given in § 36 is (from the context) an ordinary minimum.
3. Discussing the present subject with the author, a Naval officer of high rank not only expressed the opinion that the concentration of the fire of two ships on one is impracticable under modern conditions, but further stated that if he were fighting two ships against two ships of an enemy, he would bring one of his ships into action first, and only throw the other into the fight when the fire control mechanism of the enemy, i.e., observation and fighting tops, telephones, etc., had been carried away or disabled. This view is the opposite extreme to that held and advocated by the author. In any case it is not thus that Nelson fought.