During the battle the Royal Flying Corps had been active over the enemy, and, as has been shown, reported his movements fully day by day. The machines which worked direct with the corps had supplied much useful tactical information, which was passed on direct to the corps commanders as soon as the machines landed. The observers usually reported by word of mouth, and so were able to convey a full and true impression. They reported which river-bridges were broken and which intact, and they dropped messages on to the advanced British infantry in places, warning them of danger ahead. They sometimes located for corps commanders the head of the leading troops of their corps. After a three days' stay at Melun, the headquarters of the Flying Corps moved on the 7th of September to Touquin—the first move forward since the retreat from Mons. At Pezarches, about a mile away, a field was chosen for an aerodrome. Fighting had taken place there, and small one-man trenches had to be filled in before any machine could land. On the 9th of September headquarters moved forward again to Coulommiers, and on the 12th to Fère-en-Tardenois, which place became the headquarters for the battle of the Aisne. Here the squadrons were established at Saponay, some two miles to the north-west. For many long months and years the Flying Corps was not again to be employed in a war of movement against a powerful European army, so that the work they did from the time when they arrived at Maubeuge to the time when they settled at Fère-en-Tardenois has a unique value. The French Commander-in-Chief paid tribute to their skill. His message ran: 'Please express most particularly to Marshal French my thanks for the services rendered to us every day by the English Flying Corps. The precision, exactitude, and regularity of the news brought in by them are evidence of their perfect organization and also of the perfect training of pilots and observers.'

The weather during the early part of the Marne battle had been excellent for flying. The air had been still and the heat tropical. On the 9th of September, the critical day of the battle, the weather broke, and for the next few days there were violent storms and heavy rains which greatly impeded air work of any sort. The worst of these storms occurred on the night of the 12th of September, when the squadrons had newly arrived at Saponay. Four machines of No. 5 Squadron were completely wrecked, and others damaged. Lieutenant L. A. Strange saved his Henri Farman machine, which had made a forced landing, by pushing it up against a haystack, laying a ladder over the front skids, and piling large paving-stones on the ladder, using hay twisted into ropes for tying down the machine. A diary of No. 3 Squadron records that when the machines of that squadron arrived at Saponay, about five hours before the transport, 'a terrible storm was raging, and before anything could be done to make the machines more secure the wind shifted, and about half the total number of machines were over on their backs. One Henri Farman went up about thirty feet in the air and crashed on top of another Henri Farman in a hopeless tangle. B.E.'s of No. 2 Squadron were blowing across the aerodrome, and when daylight arrived and the storm abated, the aerodrome presented a pitiful sight. The Royal Flying Corps in the field had probably not more than ten machines serviceable that morning.... Hangars were not yet issued.' The protection of machines from accidents like this became comparatively easy when the line of battle was stabilized and fixed aerodromes were made.

On Sunday, the 13th of September, the Allied armies had crossed the Aisne, but were held up by the enemy line of defence which, ran along the heights from east of Compiègne to north of Rheims. There was dogged fighting, with attacks and counter-attacks, but little or no progress was made. The Germans had regained the initiative, and the British army was forced to dig itself in along the line of battle. On the 18th of September General Joffre changed his plans and began to push forces up on the Allied left in order to envelop the German right flank. To give this movement a chance the enemy had to be held on the front, and the cavalry were called on to take their turn in the trenches—a duty which before long became very familiar to them. But the Germans extended and reinforced their line for a similar outflanking movement. These enveloping attempts did not cease until the opposing armies were ranged along a line of trenches stretching from the Swiss frontier to the coast of Belgium.

During the battle of the Aisne, from the 12th to the 15th of September, the British forced the passage of the river and captured the Aisne heights including the Chemin des Dames. Thereafter fighting degenerated into a sullen trench warfare, culminating on the 26th of September and the two following days in a series of fierce attacks by the Germans. These attacks were repulsed and were not again renewed.

On the 12th of September Lieutenant L. Dawes and Lieutenant W. R. Freeman, of No. 2 Squadron, had a notable adventure. They left in the morning to carry out an aerial reconnaissance to St.-Quentin. A little south of Anizy-le-Château, between Soissons and Laon, their machine began to rock and vibrate in the air, as if the tail were loose. They planed down at once, and landed in a small field, finishing up in a wood, where they damaged their undercarriage, wings, and airscrew. Large German columns were on the roads on both sides of them, within about two hundred yards. Taking only a biscuit and some tubes of beef extract with them, they hid in another wood close by. Some German cavalry came up to the machine, and then went all round the first wood, but found nothing, and after an hour and a half went away. The two officers lay hid until the evening, and then started in the direction of the Aisne, some eight miles distant. During the night they passed several German pickets, but the war was young, the spirit of exhilaration still prevailed in the German army, and the pickets were making so much noise that they passed unobserved. At 3.0 in the morning they reached the Aisne, where they lay down and slept. At 6.0 they were wakened by the firing of a gun close by, and realized that they were in front of the German position. German cavalry patrolled the road in front of them, and they were under heavy shell-fire from the British. They swam the Aisne, dried their clothes in a house by the canal, and then walked to the British guns, which were still in action. They were given food by the Third Cavalry Brigade, and were taken back on a supply column to rejoin their squadron after an absence of more than two days. It might be supposed that their troubles were now at an end, but they had yet to face their squadron commander, Major Burke, who sternly rebuked them for violating the order that no two pilots should fly together in the same machine.

The work of observation now entered a new phase. When armies are in fixed positions movement behind the front and along the lines of communication does not greatly vary from day to day. The Flying Corps were employed to map out the enemy's chief railheads, his aerodromes (which were surprisingly numerous), his camps, and his dumps. They began also to observe the positions of enemy batteries in order to range them for our own artillery, and they made some attempts to take photographs from the air of the enemy trenches and lines of communication.

Maubeuge had fallen on the 7th of September and, in addition to the Seventh Reserve Corps and other troops, the siege artillery which had been used to reduce Maubeuge was brought down to the Aisne, and the British guns were outranged and outnumbered. The spotting of hostile batteries became an operation of the first importance, and the Flying Corps quickly rose to its opportunities. When trench warfare began, the aeroplanes attached to corps commands took up artillery officers daily from each division over the German batteries. The positions of these batteries were noted on maps, and the maps were sent in every day to the divisional artillery commander, who allotted the targets to his batteries. When any part of the British lines was shelled, information was obtained from the air and orders were given to those of our batteries which could best reply, to concentrate on the enemy's guns. The wireless machines of No. 4 Squadron had been attached to the army corps direct during the battle of the Marne, but their opportunities had been few. On the Aisne they were first used to observe for the artillery. Two pioneers of wireless telegraphy are associated in work and in memory with these early attempts at wireless co-operation with the artillery—Lieutenants Lewis and James. Donald Swain Lewis had joined the Royal Engineers in 1904, and, after qualifying as a pilot in May 1912, had transferred to the Royal Flying Corps in December 1913. By example and precept he had done all that he could before the war to adapt wireless telegraphy to the uses of the Flying Corps and to convince others of its necessity. Before the battle of the Aisne ended he had won his victory. He was in the habit of going out alone in a B.E. machine, piloting the machine and operating the wireless at the same time. A brother-officer noted of him in a diary: 'Lewis, R.E., came in from spotting with his machine shot full of holes; I believe he likes it!' Later on in the war, at home and in the field, he continued his work. In April 1915 he was appointed to command No. 3 Squadron, in succession to Major J. M. Salmond, and did much to maintain and advance the great reputation of that pioneer among squadrons. After a spell at home during the winter of 1915-16, he returned to France in February 1916, to command the Second Wing, co-operating with the Second Army in the Ypres salient. By this time he held the rank of lieutenant-colonel, but he continued to fly over the enemy lines. On the 10th of April 1916, flying a Morane parasol, east of Wytschaete, with Captain A. W. Gale, an officer of the Trench Mortars, as passenger, he was brought down by a direct hit from the enemy's anti-aircraft guns. He had been showing Captain Gale some of the objectives on which the trench mortar fire had been directed during the week, and was killed in action while he was carrying out the duties of that artillery observation which he had done so much to perfect.

Baron Trevenen James had been a mathematical scholar and head of his House at Harrow; in 1907 he passed into Woolwich, and two years later was commissioned in the Royal Engineers. He was early interested in aviation; in June 1912, after only three days' practice, he obtained the Royal Aero Club certificate at Hendon, flying a Howard Wright biplane. In April 1913 he joined the Military Wing of the Royal Flying Corps, and was at once employed in carrying out experiments with wireless. In December 1913 he was joined by Lieutenant Lewis, and the two became famous for the theory and practice of their craft. On the outbreak of war Lieutenant James was attached to No. 4 Squadron for wireless duties; when in September 1914 the headquarters wireless telegraphy unit was formed, under the command of Major H. Musgrave, at Fère-en-Tardenois, Lieutenant James was attached to it, and shared with Lieutenant Lewis the duty of reporting by wireless over the fire of the enemy guns. Like Lieutenant Lewis, he was subsequently killed in the air. On the 13th of July 1915 his commanding officer reports: 'He was observing from the aeroplane alone, as he generally did. He was ranging a battery, and was being heavily shelled. His machine was hit by a shell, and was seen to dive to the ground from a great height. The Germans dropped a note from one of their machines saying that he was dead when he fell.... He met the end I am sure he would have wished for—if it had to be—suddenly, alone, and doing his duty.'

These two, then, Lieutenants Lewis and James, had been untiring in their enthusiasm and perseverance during the years before the war. On the Aisne their reward was granted them. 'I wish to express', says General Sir Horace Smith-Dorrien in a telegram dated the 27th of September 1914, 'my great admiration for the splendid work the Royal Flying Corps is doing for my Corps from day to day. Nothing prevents them from obtaining the required information, and they frequently return with rifle or shrapnel bullets through their aeroplane or even their clothing, without considering such, to them, ordinary incidents as worth mentioning. To-day I watched for a long time an aeroplane observing for the six-inch howitzers for the Third Division. It was, at times, smothered with hostile anti-aircraft guns, but, nothing daunted, it continued for hours through a wireless installation to observe the fire and indeed to control the Battery with most satisfactory results. I am not mentioning names, as to do so, where all are daily showing such heroic and efficient work, would be invidious.' Lieutenants Lewis and James are now beyond the voices of envy, and their names may fitly be recorded in the memory of their country.

One of the earliest of the messages sent down by wireless from the air is dated the 24th of September 1914. It is worthy of full quotation: