THE conflicts of armies have left their mark across history from the plains of Marathon to the woods of the Argonne. Sea power has guided the course of nations, often dominant over all other factors, from Salamis to Jutland. To war by land and sea we have added combat in a third element, more dreadful in its potentialities than either of the older forms, warfare in the air. The late European war offered but a foretaste of what may come when things that were the imaginings of fictionists a decade and a half ago are realized in grim truth and great forces soar aloft to batter each other in the skies, raining death and destruction on the earth below. The picture is not one to contemplate with calmness, and men react to it according to their various habits of thought. Some seek to develop defense against aircraft, others seek defense against war.

To analyze the activities of the first group would be to risk becoming a partisan in the dispute long and bitterly waged between the believers in the supremacy of the capital ship and those who uphold the merits of its foes below and above the surface of the water.

No one, strong though his belief in the capital ship or in the infantryman may be, denies to aircraft a place of first-rate importance in the warfare of the future, whether conducted primarily on land or at sea. The place may or may not be one of supremacy so clear as to render other factors relatively unimportant; but all are agreed that, as between two armies or navies even approximately of the same class at the surface, clear control of the air would decide the issue. It is in the air that the military rivalries of the Powers are now developing most rapidly and most dangerously.

The airplane is a deadly weapon, but its deadliness is inversely proportional to the distance at which it strikes. We in the continental United States have nothing to fear, for the present, from aerial attack coming directly from another continent; and it is hard for us to visualize air power in the terms in which it appears, for example, to France. The extreme range of flight of any present-day heavier-than-air craft is only a little more than two thousand miles without pausing to refuel, and there is no prospect that that can be raised to more than four thousand miles, or five at the most, with materials now available and with machines of a form even approximately similar to those now used. The effective military range, the distance to which an airplane can be expected to fly carrying enough projectiles to do any real harm and with a quantity of fuel sufficient for return to the starting-point after the accomplishment of the mission, does not now exceed eight hundred miles and is unlikely to be more than doubled. To us that means safety. But to France it means that Paris lies open to direct assault from within the territories of any of at least three possible enemies, and to Englishmen it indicates that the insularity which has ever been Britain's most cherished bulwark is losing its magic. Sea power alone is no longer competent to hold an island state free from attack.

Air power cannot be met solely from the ground. It must be opposed in the air, and it is the fear of an aggression against which there will be no defense which moves Great Britain and France to undertake more and more expansive preparations. As France, goaded onward by the fear of a sudden renaissance of German aerial strength at the beginning of a war of revenge, has increased her orders for military aircraft and granted to the French aircraft industry subsidies growing progressively more liberal, Government officials in Whitehall and M. P.s at Westminster have observed events on the Continent with grave forebodings and hastened to add new squadrons to the Royal Air Force to meet the growth of French air power. The spirit of the conference at Locarno has tended towards a retardation of the competition, but there is no indication of intent to take backward steps from points already reached.

Without conscious desire in any quarter, simply as a result of the universal wish for security and for a sure weapon of defense, the world is in danger of drifting on into a race of aerial armaments paralleling that naval competition which marked the years immediately preceding the late war. The need for a check is urgent.


The problem of the control of aerial armament is not an easy one. It presents technical puzzles far more difficult to unravel than those which attended on the simple limitation of capital ship tonnage, and neither at Washington nor at Geneva has a satisfactory basis of procedure as yet been found. Perhaps, indeed, the only ideal solution would be that offered by a contributor to a recent discussion of the law of the air before the Grotius Society, who proposed that the manufacture and operation of aircraft, for any purpose whatever, should be rigorously forbidden, and that "the public should be educated to regard aviators as moral outlaws."

There are several practical difficulties in the way of visiting that cruel and unusual punishment upon the unfortunate men who fly, perhaps the most serious being that no government would agree to it. No government ties its own hands in the study of means of national defense. The Powers which met at Washington set their seals to an undertaking to refrain from the use of gas in war, but they made no promises to refrain from the study of war gases and the best means of producing them in an emergency. The need of readiness for retaliation in kind on a desperate enemy who throws aside the rules of war is fundamental.

Even could suspicion be swept away, however, the abolition of human flight would be impracticable for reasons obvious to everyone who has followed the course of development of air transport since the war. Aircraft have come to fill too large a place in the community to be spared. In the carriage of mails, in the making of photographic surveys, in the detection of forest fires, and in a score of other capacities, some spectacular, some humble, they cannot be dispensed with. In analyzing their place in war and the means to be adopted for controlling their activities, we must accept their existence as one of the basic hypotheses of the problem.


The reduction or limitation of preparations for air warfare is important primarily as a step towards the suppression of friction between nations, and in particular towards the elimination of that mutual fear which, while it exists, makes a steady march towards war almost inevitable. The material saving may be far from negligible, but it is unlikely that budgets can be made to show any such impressive transformation as is possible by the limitation of capital ship construction and maintenance.

The primary gain is moral, not economic. Limitation of naval armaments is first of all a step away from world bankruptcy. Limitation of aerial armaments is first of all a step toward world peace.

It is none the less true, however, that any scheme of reduction or limitation will be absolutely dependent for its effectiveness on the good faith of all the parties and, furthermore, on a general initial confidence in the good faith of others. Up to a certain point competition in the building of aircraft may be met and checked by international agreement. Beyond that point nothing can be done, for fear will have destroyed confidence and the contest of national forces will go on, until at last the unstable structure of peace topples and the squadrons feverishly recruited and equipped are launched against each other. It is essential that the malady be taken in its earliest stages, or there is little hope that anything can be accomplished.

Good faith and mutual confidence are necessary because of the special difficulties of the problem. Over the construction of capital ships a surveillance of a certain effectiveness can be maintained. Such ships cannot be built over night, and they cannot well be built in secret. The number of yards in which battle cruisers can be laid down is definitely limited and their location is known. Work might conceivably be undertaken in a yard closed to the public as a military area, and the naval attachés of foreign powers might be kept from learning just what was going on, but they could hardly be kept from a clear realization that something was amiss. It would be difficult in the extreme for a party to the Naval Treaty of Washington, to take a concrete example, to go materially beyond the limits set by the treaty for new construction and yet preserve even a superficial appearance of honesty.

The situation with respect to aircraft is very different. Parts of airplanes may be made in modest shops in a score of different cities, and they need not even be brought together for assembly until the time when they are needed in service. After a satisfactory type has been developed, the individual machines are cast almost as much in one pattern as Ford cars, and interchangeable parts may wait five years after manufacture before being put together. A skilful distribution of orders would make it possible to build five thousand machines in a couple of years in a populous and highly-industrialized country without permitting the most observant and energetic of aliens, unless backed by a spy system of considerable magnitude, to detect a ripple on the surface.

A still greater difficulty lies in the speed with which aircraft can be produced. It is unlikely that a capital ship not already under construction at the beginning of a war will be ready for use before its end, but an airplane can be designed and built, under pressure, in a couple of months and duplicated in hundreds within half a year. A government which determined to throw overboard all treaty restrictions at some designated future time and made its plans accordingly would be able to bring an air fleet into existence almost as if by the waving of a wand.

The close similarity of certain commercial and military aircraft, and the similarity in all cases of certain parts such as the wings, constitutes another problem. The equipment for an air force may be built up under the guise of commercial activity. Even if that were not to be done to the extent of using in commercial operation machines designed especially for military ends, truly commercial airplanes might serve a military purpose, if unopposed by machines of specialized military type, just as the vessels of a merchant marine might form effective units of a naval force unlikely to meet with any enemy fleet of hitting power substantially greater than its own. The late Admiral Mahan took occasion, in his writings on naval strategy, to urge the importance of a reserve, even though made up of ships of little strength and obsolescent type, for even these inferior craft might become the decisive factors in battle after the first-line ships of the two contending forces have eliminated each other. The commercial airplane is but a poor instrument of war, and it should never be built with possible use in war in view, but it would be used and would prove an important factor in a campaign where no up-to-date fighting and bombing craft were engaged.

It is, therefore, hopeless to expect that any state will limit its strength in the air to a very small fraction of the numerical strength in commercial aircraft of any possible adversary. Each government will claim the inalienable right to maintain a standard of air defense such as will insure its ability to keep at least a small group of fighting machines and pilots on every front where operations might take place in case war breaks out. Such a force would serve the purpose of a "fleet in being," presenting a strategic threat which would keep the enemy from attempting the use of commercial types and others inferior from a military point of view. If the war of 1914-1918 had been fought under the conditions of 1925, for example, the commercial airplanes of the Allied nations could have bombed cities and munitions plants far behind the German lines, unless the Germans had maintained home defense squadrons such as the British kept at home to meet the Zeppelins. Against aerial defense the heavy and unarmed and usually comparatively slow commercial machine would have little chance.

The standards of air power are likely to be more absolute, less relative, than those which govern the scale of navies or even armies, for the scope of aerial operations is wider than that of either sea or land alone and the differences between military and commercial airplanes, although very real, are less evident and important than those between war vessels and the units of the merchant marine.

Given good faith among the nations, much can be accomplished in the reduction by mutual agreement of the burden of preparation for air war; without the confidence created by trust in each other's good intentions, we can do nothing. The limitation of aerial armament could hardly be attempted under physical conditions more favorable, or psychological conditions worse, than those which have attended the enforcement of the conditions imposed on Germany under the Treaty of Versailles. The Allies had all the power. German opinion never had to be consulted in the making of the regulations designed to insure against preparations for a war of revenge. The inspection and supervision of German aircraft factories and flying fields could be carried out with a prying thoroughness which of course could not be paralleled in making inquiry into the enforcement of a treaty amicably entered into by friendly nations. It would be as impracticable for Great Britain and France, for example, to watch each other's aerial operations in the way that they have sought to watch Germany's as it would be for us to adopt Dawes Plan procedure and put an American transfer agent in the Bank of France to administer its policy for the primary benefit of American creditors. Nevertheless, notwithstanding the special advantages which have attended their framing and enforcement, the restrictions laid on Germany accomplished their object in a lame and incomplete manner. Inadequate to their aim in some respects, they were excessively restrictive of German commercial flying in others. They engendered a bitterness which led straight to retaliatory legislation and attempts at evasion. Prohibitions of naval activity could be enforced; regulations applied to aircraft have proven both less effective and more irksome.

The foregoing paragraphs were not written as a counsel of despair. There is reason to hope that a conference on aerial armaments would bring gains justifying its convocation, but if too much should be attempted nothing would be done. Responsible statesmen must keep their feet on the ground, even though they deal with matters aerial. A conference once called must gain some measure of success. Should it fail, the resultant jealousies and nervous tension would make a situation far worse than before. Wherever the lead be taken, the invitation to the Powers must be preceded by a careful consideration of the possible extent to which limitation might be carried and the principles on which limitation should be based. The preliminary meeting at Geneva should be welcome for that purpose. Just as Secretary Hughes presented at the very first session of the Washington conference a complete and detailed program for the scrapping by the great naval Powers of certain specified vessels and for the limitation of further construction, acting before jealousies and suspicions had had time to crystallize and going far to insure success, so here a path of procedure must be marked out in advance. A course must be charted, not left to determination from day to day by the fickle breezes of partisan oratory.


The definition of a reasonable absolute standard of aerial armament rests on many variables, technical, strategic, economic, and political. The figures must be based exclusively on considerations germane to air power, quite different from those bearing on sea power. No such simple expedient as the extension of the 5-5-3 ratio from naval vessels to naval and military aircraft would suffice.

Whatever agreement might be reached on ratios, it would be of only temporary value, and would have to be subject to easy revision as conditions change and as aircraft develop still further in efficiency and power. Naval construction is far more standardized than that of airplanes and airships, but already the Limitation of Armaments Treaty has encountered an unforeseen pitfall in the construction by the British of two ships which, while counted as battleship tonnage, seem likely from preliminary reports to incorporate many of the features of aircraft carriers and to increase British strength in mobile aircraft bases beyond that foreseen when the limit of 135,000 was set on British and American carrier tonnage. The installation of catapults for projecting airplanes from ordinary battleships has a similar influence on the potential air strength of a fleet. The same sort of difficulty will be encountered in the administration of any iron-clad rules laid down for the apportionment of aircraft and designed to stand over any very considerable period. If the time is to be fixed arbitrarily, four years would be long enough before thorough revision. A specification of the life of a treaty should in any case be supplemented by provisions that a conference to consider proposals for modifications or abrogation should be called at any time at the request of any two or three parties. It should also be clearly set forth that revision or, failing an agreement on a new form of pact, complete abandonment of limitation should be automatic in case of certain technical contingencies or of serious difficulties between a state which was a party to the treaty and one which was not.

In particular, revision should be undertaken if and when there is produced anywhere in the world an airplane shown to be capable of carrying a bomb or commercial load of 1,500 pounds weight for two thousand miles and returning home without stop. When that development has been achieved the incidence of the menace of aerial attack will be on the point of shifting, and we shall need in America an air force much stronger, relatively to that of other countries, than we require now.

A specification of the number of aircraft to be maintained in service, taken alone, would mean little more than would a bare statement of the number of ships making up a navy. It is necessary to go farther and to apportion the airplanes and airships among the several general types which might be used in war, types of which the relative importance differs in different countries. That brings once more into question the details of the methods of limitation to be adopted. On what basis of measurement of military usefulness, on what definition of a military airplane, is it likely that the nations could be brought to agree? The definition will be a very involved and technical one when it is written, and space need be given here only to the broadest outline of its possible bases and of the most important of the precautionary clauses which would have to be written into the treaty.


Perhaps the most obvious of possible restrictions would be one directed against armament. Nothing could be simpler on paper than to limit the number of airplanes which may be constructed with provision for the carriage of bombs or the mounting of machine guns. Unfortunately, as the President is rumored once to have remarked of an alluring proposal expounded to him at great length, "twon't work." The airplane is not yet enough of a flying battleship to require a permanent armament installation, and while it is true that a military airplane is exceedingly inefficient in commerce, military machines could nevertheless be built under the guise of commerce carriers, with the structure so designed as to carry the bomb racks or guns or both and to facilitate their quick attachment. The terms of limitation must apply directly to the aircraft, not to their accessory equipment.

Confronted with this same problem when they undertook to clip the claws of the German war eagle, the Allied Powers placed their chief dependence on specification of performance, of the speed and climb which must not be exceeded by new machines. It was considered necessary that the permissible figures be set very low, so low as to prevent the construction and use of such machines as are used by the Air Mail in this country and by eighty percent of the French and British passenger lines. Neither in method of enforcement nor in specific nature of the technical restrictions imposed do the rules laid down under the Treaty of Versailles serve as a direct basis for an agreement for the limitation of aerial armaments.

Something could, however, be done with performance specifications. No commercial airplane needs to fly at a speed in excess of 140 miles an hour, and there would be no serious hardship in the setting of a figure ten miles lower still. A pursuit, or fighting, machine would, on the other hand, be of little use in aerial combat under modern conditions unless its speed were over 150 miles an hour. Observation airplanes, carrying a crew of two, are also being designed now to approach very closely the 150-mile point. A limitation of the number of machines capable of flying at 140 miles an hour or more to be produced in each year would therefore be, in essence, a limitation on the number of fighting airplanes.

The acceptance of such a limit is at least conceivable, although it would be a blind and foolish optimism which would overlook or brush aside the very grave administrative difficulties, which serve to emphasize once more the imperative necessity of at least an approximation to good faith. It is often easy to design an airplane so that engines of several different types can be installed interchangeably. Such a machine might be regularly fitted with a power-plant giving a very moderate speed, yet changed into a real combat type within a few hours by the mounting of a much more powerful engine secretly kept in storage for that purpose. Trickery is far easier here than in dealing with battleships, which are set up as complete units incapable of rapid and important changes in form, although perhaps less readily practised than in connection with poison-gas treaties. The possibility of its existence must always be taken into account when the treaty is being drawn, and not simply allowed to rise as a disquieting spectre after the document has taken effect. The need for a degree of mutual confidence such that suspicion of each other's integrity is not too unreasoning and continuous has already been emphasized, but no amount of confidence would justify writing specifications so loose in form or so difficult to enforce that they constitute a positive invitation to chicane.

There seems to be no way of overcoming completely the possibility of evasion. A force of inspectors would have to be placed in every factory suspected of ability to build airplanes or their engines, and the work would have to be watched at every step, both in the shop and the drafting-room. A single air attaché with two or three assistants would have but little chance of telling in detail what was going on behind the scenes in the nominally friendly country to which he might be assigned. The most that can be done, beyond the point where good faith from the other parties to a treaty can be depended upon, is to make sure that the machines are not actually being mustered into service beyond the numbers agreed upon and in condition for immediate use in war. Even that will be possible only if the treaty, in providing for limitation, provides also for definite rights of surveillance. Failing such provision, there is nothing to prevent the setting aside of a large portion of a nation's territory as a military reservation, into which no foreigners are allowed to enter, an area within which military preparations can be carried on without regard to rules and secure from intrusion. There is some precedent for such action. Carried far enough, it would render nugatory any attempt at limitation, whether of armies, navies, or aircraft.

Performance limitation would not have to rest on maximum speed alone, although that factor is as easy as any other to deal with and is probably more effective than any other in distinguishing between commercial and military types. The very large military airplanes, however, do not fly very rapidly and must be cared for otherwise. They could be held in check by a direct limitation on size, and apparently in no other way, unless rules can be worked out to prevent the design of commercial airplanes with provision for bomb racks. That, as already remarked, seems more than doubtful. Limits on size would be unfortunate, for the giant airplane may be badly needed in commerce and is already appearing, and they are not likely to be set up by the voluntary act of free states feeling a real interest in aeronautical development. The bombing machine probably must go unrestricted except for a general agreement, of questionable value, not to build more than a specified number of airplanes directly and admittedly destined for bombing use.

Another possibility, one which cannot be argued without going into a mass of technical detail, would be the setting up of specific relations between weight and power, the factors most responsible for governing performance. All such limits are, however, as has already been sufficiently emphasized, unsatisfactory. The final answer does not lie in specifications of performance.

One way out, and perhaps the most promising of all, lies in direct control of the commercial airplane and its use. If air lines are to be run, as some of them have been, with machines having an underlying military purpose and readily capable of such adaptation that they could serve for bombing or observation in a district where the enemy still had fighting craft in the air, they will operate very inefficiently and at a loss, for the "rolling-stock" will be too uncomfortable to attract passengers and too uneconomical to keep the fares and freight rates reasonably low. The government will then have to come to the rescue with a subsidy, and in the control of that subsidy is found a possible solution to the vexed problem of distinction between the commercial and the non-commercial. A limit written either in terms of absolute expenditure for subsidies, direct or indirect, or of grant per mile flown on air lines open to the patronage of the citizens of all nations under like conditions for all would at once serve as a spur to progress towards better machines for air transport and a check on the use of transport as a cloak for preparation for aerial war. In the long run, such a limit should be for the benefit of all.

Aircraft cannot fly without pilots, and military pilots cannot be trained overnight. An absolute limitation on the number trained each year for any purpose, coupled with an undertaking to keep the activities of private flying schools under government control, would be a natural corollary of any sort of treaty for the control of aerial armaments. In America, for example, there does not now exist and is not likely to exist in the near future an actual need for the training of more than two hundred pilots each year beyond the number, still rather small, of private operators who purchase airplanes and fly them for amusement. The building up of a comparatively inactive reserve force subject to annual call for renewed flying practice is of course desirable, and in fact necessary, if other states are to have such a reserve, but the privilege is one which all countries might well relinquish together. Commercial flying will not in the very near future provide berths for more than a few score new men a year. A definite agreement on the number to be trained under each flag, of course subject to frequent periodic adjustments to meet the developing needs of commerce, would be the most effective of safeguards against competition in aerial armament. It would become increasingly effective with the passage of time during the next decade, for the vast numbers of young men who learned to fly during the war, still available in case of planned aggression or of defensive need, will not long be of an age for military flying. By 1935 at latest an almost wholly new generation will have come upon the aerial scene.

At some time in the future, on the other hand, an attempt to control the teaching of pilots will lose its usefulness because flying will have become a matter of course and it will be as impossible to keep a check on the number of those who practise the art as it would to keep an international roster of all operators of automobiles now. Already it is a simple matter to learn to take an airplane into the air and set it down again, but military flying requires a long and specialized training, likely to be given at only a few stations in each country. The problem of surveillance to insure against deceit is still a troublesome one, but less troublesome than if restrictions were applied solely to the machines.


If the problem is examined with an unswerving realism, it has to be accepted that the methods of restriction which would be most effective are precisely those which the nations would most hesitate to adopt. It might be easy to get agreement on a certain number of military airplanes for each state, and even to hit upon an acceptable definition of a military airplane, although the second step would be much less simple than the first, but surveillance would be resented and suspicion would be swift to develop. To secure accession to a subsidy limitation would be far more difficult. Military and economic considerations are inextricably connected in the allocation of transport subsidies, and any promise to confine the subsidy within specified bounds would be subject to parliamentary and press attack as an unwarrantable surrender of the right of free action in respect of a domestic policy. It might be possible to overcome those objections if the difficulty of the problem of control and the importance of finding a generally satisfactory solution were made sufficiently clear to the public at large, but their certain existence must be foreseen.

Almost the same words could be used of the proposed limit on the training of pilots. The permitted figure would of course be set so high that there would be no interference with the rights of the private owners of airplanes desiring to learn to operate their own machines, but any nation would be hesitant about giving up the privilege of maintaining and steadily adding to a substantial reserve. There again the obstacles might not prove insuperable if the relations among the great aerial Powers were such that each could feel reasonably secure against an early conspiracy of its neighbors.

Recapitulation of possible methods and of the barriers in the path of each leads back always to the necessity of that feeling of security. The outlook for effective limitation is far from bright, but a conference called at a favorable season and after due preparation of the path should lead at least to a temporary readjustment and to a partial clearing up of such veiled threats as some states now see in the maintenance by others of air power which may actually be for colonial or other kindred service. Beyond that rather half-hearted prophecy of probable benefit one can hardly go at present unless a hope for success is permitted to dominate an analysis of conditions as they exist.

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  • EDWARD P. WARNER, Professor of Aeronautics at the Massachusetts Institute of Technology; former Technical Assistant in Europe for the National Advisory Committee for Aeronautics
  • More By Edward P. Warner