The reconnaissance resulting in the most valuable information of all, and, I think, during the whole of the war, was that of September 3rd, during the critical operations on the Marne, which formed one of the decisive battles in the world's history, when von Kluck's turning movement to the south-east against the French left was accurately reported and Marshal Joffre was enabled to make his dispositions accordingly. "The precision, exactitude and regularity of the news brought in," he said in a message to the British Commander-in-Chief, "are evidence of the perfect training of pilots and observers." The reports of the German air service, on the other hand, would appear from von Kluck's movements to have been of no assistance to him. The system adopted from the first was for the pilot or observer, or both, immediately on their return to bring their report to R.F.C. Headquarters, whence the Commander, or his staff officer, accompanied them to G.H.Q., where the map was filled in in accordance with the report. G.H.Q. could then ask questions and obtain any further information which the observer could give, while R.F.C. Headquarters could ascertain what further reports were most urgently required. The form of the reports, which were ready printed, had been most carefully thought out at R.F.C. Headquarters in peace and experimented with at the Concentration Camp. The maps thus compiled at G.H.Q. from air reconnaissance reports between August 31st and September 3rd were of vital interest, though it was sometimes very difficult to get the information put on the map for prompt consideration. For instance, at Dammartin on the evening of September 1st, when it was thought that German cavalry were within a few miles, G.H.Q. made a very hurried departure, and I was unable to find anyone to whom to give very important reports. 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.