Ever since the days of Jules Verne no theme has proved so popular in fiction as fighting in the air. It was a subject which lent itself to vivid imagination and spirited picturesque portrayal. Discussion might be provoked, but it inevitably proved abortive, inasmuch as there was a complete absence of data based upon actual experience. The novelist was without any theory: he avowedly depended upon the brilliance of his imagination. The critic could only theorise, and no matter how dogmatic his reasonings, they were certainly as unconvincing as those of the object of his attack.

But truth has proved stranger than fiction. The imaginative pictures of the novelist have not only been fulfilled but surpassed, while the theorising critic has been utterly confounded. Fighting in the air has become so inseparable from the military operations of to-day that it occurs with startling frequency. A contest between hostile aeroplanes, hundreds of feet above the earth, is no longer regarded as a dramatic, thrilling spectacle: it has become as matter-of-fact as a bayonet melee between opposed forces of infantry.

A duel in the clouds differs from any other form of encounter. It is fought mercilessly: there can be no question of quarter or surrender. The white flag is no protection, for the simple reason that science and mechanical ingenuity have failed, so far, to devise a means of taking an aeroplane in tow. The victor has no possible method of forcing the vanquished to the ground in his own territory except driving. If such a move be made there is the risk that the latter will take the advantage of a critical opportunity to effect his escape, or to turn the tables. For these reasons the fight is fought to a conclusive finish.

To aspire to success in these combats waged in the trackless blue, speed, initiative, and daring are essential. Success falls to the swift in every instance. An aeroplane travelling at a high speed, and pursuing an undulating or irregular trajectory is almostimpossible to hit from the ground, as sighting is so extremely difficult. Sighting from another machine, which likewise is travelling rapidly, and pursuing an irregular path, is far more so. Unless the attacker can approach relatively closely to his enemy the possibility of hitting him is extremely remote. Rifle or gun-fire must be absolutely point blank.

When a marauding aeroplane is espied the attacking corsair immediately struggles for the strategical position, which is above his adversary. To fire upwards from one aeroplane at another is virtually impossible, at least with any degree of accuracy. The marksman is at a hopeless disadvantage. If the pilot be unaccompanied and entirely dependent upon his own resources he cannot hope to fire vertically above him, for the simple reason that in so doing he must relinquish control of his machine. A rifle cannot possibly be sighted under such conditions, inasmuch as it demands that the rifleman shall lean back so as to obtain control of his weapon and to bring it to bear upon his objective. Even if a long range Mauser or other automatic pistol of the latest type be employed, two hands are necessary for firing purposes, more particularly as, under such conditions, the machine, if not kept under control, is apt to lurch and pitch disconcertingly.

Even a colleague carried for the express purpose of aggression is handicapped. If he has a machinegun, such as a Maxim or a mitrailleuse, it is almost out of the question to train it vertically. Its useful vertical training arc is probably limited to about 80 degrees, and at this elevation the gunner has to assume an extremely uncomfortable position, especiauy upon an aeroplane, where, under the best of circumstances, he is somewhat cramped.

On the other hand the man in the aeroplane above holds the dominating position. He is immediately above his adversary and firing may be carried out with facility. The conditions are wholly in his favour. Sighting and firing downwards, even if absolutely vertically, imposes the minimum physical effort, with the result that the marksman is able to bring a steadier aim upon his adversary. Even if the machine be carrying only the pilot, the latter is able to fire upon his enemy without necessarily releasing control of his motor, even for a moment.

If he is a skilled sharpshooter, and the exigencies demand, he can level, sight, and fire his weapon with one hand, while under such circumstances an automatic self-loading pistol can be trained upon the objective with the greatest ease. If the warplane be carrying a second person, acting as a gunner, the latter can maintain an effective rifle fusillade, and, at the same time, manipulate his machine-gun with no great effort, maintaining rifle fire until the pilot, by manoeuvring, can enable the mitrailleuse or Maxim to be used to the greatest advantage.

Hence the wonderful display of tactical operations when two hostile aeroplanes sight one another. The hunted at first endeavours to learn the turn of speed which his antagonist commands. If the latter is inferior, the pursued can either profit from his advantage and race away to safety, or at once begin to manoeuvre for position. If he is made of stern stuff, he attempts the latter feat without delay. The pursuer, if he realises that he is out classed in pace, divines that his quarry will start climbing if he intends to show fight, so he begins to climb also.

Now success in this tactical move will accrue to the machine which possesses the finest climbing powers, and here again, of course, speed is certain to count. But, on the other hand, the prowess of the aviator - the human element once more - must not be ignored. The war has demonstrated very convincingly that the personal quality of the aviator often becomes the decisive factor.

A spirited contest in the air is one of the grimmest and most thrilling spectacles possible to conceive, and it displays the skill of the aviator in a striking manner. Daring sweeps, startling wheels, breathless vol-planes, and remarkable climbs are carried out. One wonders how the machine can possibly withstand the racking strains to which it is subjected. The average aeroplane demands space in which to describe a turn, and the wheel has to be manipulated carefully and dexterously, an operation requiring considerable judgment on the part of the helmsman.

But in an aerial duel discretion is flung to the winds. The pilot jambs his helm over in his keen struggle to gain the superior position, causing the machine to groan and almost to heel over. The stem stresses of war have served to reveal the perfection of the modern aeroplane together with the remarkable strength of its construction. In one or two instances, when a victor has come to earth, subsequent examination has revealed the enormous strains to which the aeroplane has been subjected. The machine has been distorted; wires have been broken - wires which have succumbed to the enormous stresses which have been imposed and have not been snapped by rifle fire. One well-known British airman, who was formerly a daring automobilist, confided to me that a fight in the air "is the finest reliability trial for an aeroplane that was ever devised!"

In these desperate struggles for aerial supremacy the one party endeavours to bring his opponent well within the point-blank range of his armament: the other on his part strives just as valiantly to keep well out of reach. The latter knows fully well that his opponent is at a serious disadvantage when beyond point-blank range, for the simple reason that in sighting the rifle or automatic pistol, it is difficult, if not impossible while aloft, to judge distances accurately, and to make the correct allowances for windage.

If, however, the dominating aviator is armed with a machine gun he occupies the superior position, because he can pour a steady hail of lead upon his enemy. The employment of such a weapon when the contest is being waged over friendly territory has many drawbacks. Damage is likely to be infficted among innocent observers on the earth below; the airman is likely to bombard his friends. For this very reason promiscuous firing, in the hope of a lucky shot finding a billet in the hostile machine, is not practised. Both parties appear to reserve their fire until they have drawn within what may be described as fighting distance, otherwise point blank range, which may be anything up to 300 yards.

Some of the battles between the German and the French or British aeroplanes have been waged with a total disregard of the consequences. Both realise that one or the other must perish, and each is equally determined to triumph. It is doubtful whether the animosity between the opposing forces is manifested anywhere so acutely as in the air. In some instances the combat has commenced at 300 feet or so above the earth, and has been fought so desperately, the machines climbing and endeavouring to outmanoeuvre each other, that an altitude of over 5,000 feet has been attained before they have come to close grips.

The French aviator is nimble, and impetuous: the German aviator is daring, but slow in thought: the British airman is a master of strategy, quick in thought, and prepared to risk anything to achieve his end. The German airman is sent aloft to reconnoitre the enemy and to communicate his information to his headquarters. That is his assigned duty and he performs it mechanically, declining to fight, as the welfare of his colleagues below is considered to be of more vital importance than his personal superiority in an aerial contest. But if he is cornered he fights with a terrible and fatalistic desperation.

The bravery of the German airmen is appreciated by the Allies. The French flying-man, with his traditional love for individual combat, seeks and keenly enjoys a duel. The British airman regards such a contest as a mere incident in the round of duty, but willingly accepts the challenge when it is offered. It is this manifestation of what may be described as acquiescence in any development that enabled the British flying corps, although numerically inferior, to gain its mastery of the air so unostentatiously and yet so completely.

All things considered an aeroplane duel is regarded as a fairly equal combat. But what of a duel between an aeroplane and a dirigible? Which holds the advantage? This question has not been settled, at any rate conclusively, but it is generally conceded that up to a certain point the dirigible is superior. It certainly offers a huge and attractive target, but rifle fire at its prominent gas-bag is not going to cause much havoc. The punctures of the envelope may represent so many vents through which the gas within may effect a gradual escape, but considerable time must elapse before the effect of such a bombardment becomes pronounced in its result, unless the gas-bag is absolutely riddled with machine gun-fire, when descent must be accelerated.

On the other hand, it is to be presumed that the dirigible is armed. In this event it has a distinct advantage. It has a steady gun-platform enabling the weapons of offence to be trained more easily and an enhanced accuracy of,fire to be obtained. In order to achieve success it is practically imperative that an aeroplane should obtain a position above the dirigible, but the latter can ascend in a much shorter space of time, because its ascent is vertical, whereas the aeroplane must describe a spiral in climbing. Under these circumstances it is relatively easy for the airship to outmanoeuvre the aeroplane in the vertical plane, and to hold the dominating position.

But even should the aeroplane obtain the upper position it is not regarded with fear. Some of the latest Zeppelins have a machine gun mounted upon the upper surface of the envelope, which can be trained through 360 degrees and elevated to about 80 degrees vertical. Owing to the steady gun platform offered it holds command in gun-fire, so that the aeroplane, unless the aviator is exceptionally daring, will not venture within the range of the dirigible. It is stated, however, that this upper gun has proved unsatisfactory, owing to the stresses and strains imposed upon the framework of the envelope of the Zeppelin during firing, and it has apparently been abandoned. The position, however, is still available for a sniper or sharpshooter.

The position in the sky between two such combatants is closely analogous to that of a torpedo boat and a Dreadnought. The latter, so long as it can keep the former at arm's, or rather gun's, distance is perfectly safe. The torpedo boat can only aspire to harass its enemy by buzzing around, hoping that a lucky opportunity will develop to enable it to rush in and to launch its torpedo. It is the same with the aeroplane when arrayed against a Zeppelin. It is the mosquito craft of the air.

How then can a heavier-than-air machine triumph over the unwieldy lighter-than-air antagonist? Two solutions are available. If it can get above the dirigible the adroplane may bring about the dirigible's destruction by the successful launch of a bomb. The detonation of the latter would fire the hydrogen within the gas-bag or bags, in which event the airship would fall to earth a tangled wreck. Even if the airship were inflated with a non-inflammable gas - the Germans claim that their Zeppelins now are so inflated - the damage wrought by the bomb would be so severe as to destroy the airship's buoyancy, and it would be forced to the ground.

The alternative is very much more desperate. It involves ramming the dirigible. This is undoubtedly possible owing to the speed and facile control of the aeroplane, but whether the operation would be successful remains to be proved. The aeroplane would be faced with such a concentrated hostile fire as to menace its own existence - its forward rush would be frustrated by the dirigible just as a naval vessel parries the ramming tactics of an enemy by sinking the latter before she reaches her target, while if it did crash into the hull of the dirigible, tearing it to shreds, firing its gas, or destroying its equilibrium, both protagonists would perish in the fatal dive to earth. For this reason ramming in mid-air is not likely to be essayed except when the situation is desperate.

What happens when two aeroplanes meet in dire combat in mid-air and one is vanquished? Does the unfortunate vessel drop to earth like a stone, or does it descend steadily and reach the ground uninjured? So far as actual experience has proved, either one of the foregoing contingencies may happen. In one such duel the German aeroplane was observed to start suddenly upon a vol-plane to the ground. Its descending flight carried it beyond the lines of the Allies into the territory of its friends. Both came to the conclusion that the aviator had effected his escape. But subsequent investigation revealed the fact that a lucky bullet from the Allies' aeroplane had lodged in the brain of the German pilot, killing him instantly. At the moment when Death over took him the aviator had set his plane for the descent to the ground, and the machine came to earth in the manner of a glider.

But in other instances the descent has been far more tragic. The aeroplane, deprived of its motive power, has taken the deadly headlong dive to earth. It has struck the ground with terrific violence, burying its nose in the soil, showing incidentally that a flying machine is an indifferent plough, and has shattered itself, the debris soaked with the escaping fuel becoming ignited. In any event, after such a fall the machine is certain to be a wreck. The motor may escape damage, in which event it is salvaged, the machine subsequently being purposely sacrificed to the flames, thereby rendering it no longer available to the enemy even if captured. In many instances the hostile fire has smashed some of the stays and wires, causing the aeroplane to lose its equilibrium, and sending it to earth in the manner of the proverbial stone, the aviators either being dashed to pieces or burned to death.

What are the vulnerable parts of the aeroplane? While the deliberate intention of either combatant is to put his antagonist hors de combat, the disablement of the machine may be achieved without necessarily killing or even seriously wounding the hostile airman. The prevailing type of aeroplane is highly susceptible to derangement: it is like a ship without armour plate protection. The objective of the antagonist is the motor or the fuel-tank, the vital parts of the machine, as much as the aviator seated within.

A well-planted shot, which upsets the mechanism of the engine, or a missile which perforates the fuel tank, thereby depriving the motor of its sustenance, will ensure victory as conclusively as the death of the aviator himself. Rifle fire can achieve either of these ends with little difficulty. Apart from these two nerve-centres, bombardment is not likely to effect the desired disablement, inasmuch as it cannot be rendered completely effective. The wings may be riddled like a sieve, but the equilibrium of the machine is not seriously imperilled thereby. Even many of the stays may be shot away, but bearing in mind the slender objective they offer, their destruction is likely to be due more to luck than judgment. On the other hand, the motor and fuel tank of the conventional machine offer attractive targets: both may be put out of action readily, and the disablement of the motive power of an enemy's craft, be it torpedo-boat, battleship, or aeroplane, immediately places the same at the assailant's mercy.

Nevertheless, of course, the disablement of the airman brings about the desired end very effectively. It deprives the driving force of its controlling hand; The aeroplane becomes like a ship without a rudder: a vessel whose helmsman has been shot down. It is unmanageable, and likely to become the sport of the element in which it moves. It is for this reason that aviators have been urged to direct their fire upon the men and mechanism of a dirigible in the effort to put it out of action. An uncontrolled airship is more likely to meet with its doom than an aeroplane. The latter will inevitably glide to earth, possibly damaging itself seriously in the process, as events in the war have demonstrated, but a helpless airship at once becomes the sport of the wind, and anyone who has assisted, like myself, in the descent of a vessel charged with gas and floating in the air, can appreciate the difficulties experienced in landing. An uncontrolled Zeppelin, for instance, would inevitably pile up in a tangled twisted ruin if forced to descend in the manner of an ordinary balloon. Consequently the pilot of a dirigible realises to the full the imperative urgency of keeping beyond the point-blank fire of aerial mosquito craft.

The assiduity with which British aviators are prepared to swarm to the attack has been responsible for a display of commendable ingenuity on the part of the German airman. Nature has provided some of its creatures, such as the octopus, for instance, with the ways and means of baffling its pursuers. It emits dense clouds of inky fluid when disturbed, and is able to effect its escape under cover of this screen.

The German aviator has emulated the octopus. He carries not only explosive bombs but smoke balls as well. When he is pursued and he finds himself in danger of being overtaken, the Teuton aviator ignites these missiles and throws them overboard. The aeroplane becomes enveloped in a cloud of thick impenetrable smoke. It is useless to fire haphazard at the cloud, inasmuch as it does not necessarily cover the aviator. He probably has dashed out of the cloud in such a way as to put the screen between himself and his pursuer.

In such tactics he has merely profited by a method which is practised freely upon the water. The torpedo boat flotilla when in danger of being overwhelmed by superior forces will throw off copious clouds of smoke. Under this cover it is able to steal away, trusting to the speed of the craft to carry them well beyond gunshot. The "smoke screen," as it is called, is an accepted and extensively practised ruse in naval strategy, and is now adopted by its mosquito colleagues of the air.