It was at the Battle of the Marne that machines were for the first time allotted to Army Corps for tactical work, while long-distance reconnaissance was carried out by other machines operating from Headquarters. Later on, this system was established as a part of our permanent organization, squadrons being allotted to, and reporting direct to, Corps for tactical reconnaissance, artillery co-operation and contact patrols, and to Armies for longer-distance reconnaissance and fighting.
The last phase of the war of movement was the race for the Channel Ports and it devolved upon aircraft to observe the enemy's movements from his centre and left flank to meet the Allied movement to the coast, to observe the movements of the four newly-formed corps which came into action at Ypres and to maintain liaison with the Belgian and British forces at Antwerp and Ostend. Information was very difficult to obtain and on one occasion I flew from the Aisne to Antwerp, under Sir John French's instructions, in order as far as possible to clear up the general situation when our G.H.Q. was in doubt as to whether Antwerp was completely surrounded or not. It was an interesting piece of work. There was a light drizzle, and the forest of Compiègne had to be flown over at about 200 feet. The B.E. could not make the distance without refilling, and although only a short halt was made at Amiens for the purpose, it was too late to fly direct to Antwerp. Instead, a landing was made in a very sticky field under light plough, which was selected from the air about 4 miles north of Bruges, to which town I rode on a borrowed bicycle. At Bruges there was great consternation and uncertainty as to the position at Antwerp, but the Commander kindly placed a large open car and its very energetic driver at my disposal to try and get through. After many difficulties we managed to find our way into Antwerp by about midnight, and I was received by the Belgian Commander. He explained that though the Germans had broken through the South-Eastern sector and his troops were very hard pressed (and pointing repeatedly to a piece of an 18-inch German shell in the corner of the room, he said, "Mais qu'est-ce qu'on peut faire avec ces choses-là!"), he hoped to be able to hold out for a time. After giving him General French's message and obtaining as much information as possible, I managed to get clear of Antwerp, reaching Bruges again at 3.15 a.m. At 4 a.m. we set out and found a very wet machine in a wetter field and after considerable difficulty and flying through the top of the surrounding hedge, struggled into the upper air on the way back to Headquarters at Fère-en-Tardennois.
During the Battles of the Aisne and of Ypres strategical reconnaissance was carried out by the few machines available at Headquarters. Shephard, the best reconnaissance officer I have ever known, who was killed later, used to fly his B.E.2 without observer over the greater part of Belgium two or three times a week and always brought in a long, closely packed, and extraordinarily valuable report. Tactical reconnaissance to a depth of 15 to 20 miles was done by units attached to Corps.
After the Battle of the Aisne, which was the turning point in the evolution from the war of movement to trench warfare, pure reconnaissance, though still the basis of air work, tended to become a matter of routine, while many new and specialized forms of it—such as air photography and artillery spotting by wireless—were developed.
Photography.
Though experiments had been made in the problem of photography from the air before the war, principally by Fletcher, Hubbard and Laws, and its value to survey was recognized, it had not become of practical utility. We only took one official camera with us to France on August 13th, 1914, and it was not until September 15th that the first attempt at air photography was made, when five plates were exposed over positions behind the enemy's lines with very imperfect results. Its great value as an aid to observation in trench warfare was, however, very apparent, fresh brains were brought to the task, Moore-Brabazon, Campbell and Dr. Swan, and by the end of the year better success was obtained, though positions even then had to be filled in by the observer with red ink. Experiments at home during 1915 led to a great improvement in lenses, and at the beginning of 1916 air photography was universal. At the Battle of the Somme new enemy positions were photographed as soon as they were seen, and the camera did invaluable work in the reconnaissance of the Hindenburg Line during the German retreat of 1917, and the taking of over a thousand photographs was a daily occurrence. On September 4th, 1917, a record of 1,805 photographs was made.
The development of air photography, very remarkable in itself, is even more so when it is remembered that the improvement in enemy anti-aircraft guns drove our machines to carry out their work at altitudes increasing up to 20,000 and even 22,000 feet, at which heights the negatives had to be as distinct as those taken at 4,000 in the earlier days of the war.
At the beginning of the Dardanelles operations our apparatus consisted of one camera, a printing frame and a dark room lamp. The first photographs were taken by Butler in April, 1915, from a H. Farman machine at necessarily low altitudes. Butler was wounded in June and was succeeded by Thomson, who alone made 900 exposures and sent in 3,600 prints.
In addition to the assistance of air photography to reconnaissance, the war gave it great impetus as the handmaid of survey and mapping. It was, in fact, the only means of mapping or correcting the maps of country held by the enemy, which in certain cases, as at Gallipoli and in Palestine, were very inaccurate.
By the end of the war photographic processes and equipment had reached a high standard of excellence. There are still, however, certain difficulties in regard to the production of accurate maps, which have not been overcome, the most obvious being the necessity of an initial framework of fixed points and of contouring. The subject is considered so important that an "Air Survey Committee," consisting of representatives of the Air Ministry, the Geographical section of the War Office, the Ordnance Survey, the School of Military Engineering and the Artillery Survey School, has recently been formed. In addition, the School of Aeronautics of Cambridge University is studying the question. The Survey of India and the Survey of Egypt are also conducting experiments.