Machines fitted with cameras photograph every inch of the defences improvised by the enemy, and, as insurance against being caught unprepared by a counter-attack, an immediate warning of whatever movement is in evidence on the lines of communication will be supplied by the reconnaissance observers. Under the direction of artillery squadrons the guns pound the new Boche front line and range on troublesome batteries.

The bombing craft are responsible for onslaughts on railways, supply depôts, garrison towns, headquarters, aerodromes, and chance targets. Other guerilla work is done by craft which, from a height of anything under a thousand feet, machine-gun whatever worthwhile objects they spot. A column of troops on the march, transport, ammunition waggons, a train, a stray motor-car—all these are greeted joyfully by the pilots who specialise in ground stunts. And at every hour of daylight the scouts and fighting two-seaters protect the remainder of the R.F.C. by engaging all Huns who take to the air.

Doubtless, when sunset has brought the roving birds back to their nest, there will be a few "missing"; but this, part of the day's work, is a small enough sacrifice for the general achievement—the staff supplied with quick and accurate information, a hundred or two Boche batteries silenced, important works destroyed, enemy communications impeded, a dozen or so black-crossed aeroplanes brought down, valuable photographs and reports obtained, and the ground-Hun of every species harried.

The German Flying Corps cannot claim to perform anything like the same amount of aerial observation as its British counterpart. It is mainly occupied in fighting air battles and hampering the foreign machines that spy on their army. To say that the German machines are barred altogether from reconnaissance and artillery direction would be exaggeration, but not wild exaggeration. Seldom can an enemy plane call and correct artillery fire for longer than half an hour. From time to time a fast machine makes a reconnaissance tour at a great height, and from time to time others dart across the lines for photography, or to search for gun positions. An appreciable proportion of these do not return. Four-fifths of the Hun bomb raids behind our front take place at night-time, when comparative freedom from attack is balanced by impossibility of accurate aim. Apart from these spasmodic activities, the German pilots concern themselves entirely with attempts to prevent allied observation. They have never yet succeeded, even during the periods of their nearest approach to the so-called "mastery of the air," and probably they never will succeed. The advantages attendant upon a maintenance of thorough observation, while whittling down the enemy's to a minimum, cannot be overestimated.

To determine how much credit for the brilliant achievement I have tried to outline belongs to the skill and adaptability of British airmen, and how much to successful organisation, would be difficult and rather unnecessary. But it is obvious that those who guided the R.F.C. from neglected beginnings to the status of a great air service had a tremendous task. Only the technical mind can realise all that it has involved in the production of trained personnel, aeroplanes, engines, aircraft depôts, aerodromes, wireless equipment, photographic workshops and accessories, bombs, and a thousand and one other necessaries.

Many thousand pilots have been trained in all the branches of war flying. The number of squadrons now in France would surprise the layman if one were allowed to make it public; while other squadrons have done excellent work in Macedonia, Egypt, Mesopotamia, East Africa, and elsewhere. Mention must also be made of the Home Defence groups, but for which wholesale Zeppelin raids on the country would be of common occurrence.

How to make best use of the vast personnel in France is the business of the staff, who link the fighting members of the corps with the Intelligence Department and the rest of the Army in the field. To them has fallen the introduction and development of the various functions of war aircraft, besides the planning of bomb raids and concerted aerial offensives. On the equipment side there is an enormous wastage to be dealt with, and consequently a constant cross-Channel interchange of machines. The amount of necessary replacement is made specially heavy by the short life of effective craft. A type of machine is good for a few months of active service, just holds its own for a few more, and then becomes obsolete except as a training bus. To surpass or even keep pace with the Boche Flying Corps on the mechanical side, it has been necessary for the supply department to do a brisk trade in new ideas and designs, experiment, improvement, and scrapping.

Although free-lance attacks by airmen on whatever takes their fancy down below are now common enough, they were unknown little over a year ago. Their early history is bound up with the introduction of contact patrols, or co-operation with advancing infantry. Previous to the Somme Push of 1916, communication during an attack between infantry on the one hand and the guns and various headquarters on the other was a difficult problem. A battalion would go over the top and disappear into the enemy lines. It might have urgent need of reinforcements or of a concentrated fire on some dangerous spot. Yet to make known its wants quickly was by no means easy, for the telephone wires were usually cut, carrier-pigeons went astray, and runners were liable to be shot. When the British introduced the "creeping barrage" of artillery pounding, which moved a little ahead of the infantry and curtained them from machine-gun and rifle fire, the need for rapid communication was greater than ever. Exultant attackers would rush forward in advance of the programmed speed and be mown by their own barrage.

Credit for the trial use of the aeroplane to link artillery with infantry belongs to the British, though the French at Verdun first brought the method to practical success. We then developed the idea on the Somme with notable results. Stable machines, equipped with wireless transmitters and Klaxon horns, flew at a low height over detailed sectors, observed all developments, signalled back guidance for the barrage, and by means of message bags supplied headquarters with valuable information. Besides its main purpose of mothering the infantry, the new system of contact patrols was found to be useful in dealing with enemy movements directly behind the front line. If the bud of a counter-attack appeared, aeroplanes would call upon the guns to nip it before it had time to blossom.

Last September we of the fighting and reconnaissance squadrons began to hear interesting yarns from the corps squadrons that specialised in contact patrols. An observer saved two battalions from extinction by calling up reinforcements in the nick of time. When two tanks slithered around the ruins of Courcelette two hours before the razed village was stormed, the men in the trenches would have known nothing of this unexpected advance-guard but for a contact machine. The pilot and observer of another bus saw two tanks converging eastward at either end of a troublesome Boche trench. A German officer, peering round a corner, drew back quickly when he found one of the new steel beasts advancing. He hurried to an observation post round a bend in the lines. Arrived there, he got the shock of his life when he found a second metal monster waddling towards him. Alarmed and unnerved, he probably ordered a retirement, for the trench was evacuated immediately. The observer in a watching aeroplane then delivered a much-condensed synopsis of the comedy to battalion headquarters, and the trench was peacefully occupied.