deed war.

Valuable reconnaissances were made during the whole Retreat from Mons to
the Marne in spite of the tremendous difficulties involved by constant
movement, transport, and the selection of new landing grounds, but, in
the words of Sir John French, "It was the timely warning aircraft gave
which chiefly enabled me to make speedy dispositions to avert danger and
disaster. There can be no doubt indeed that even then the presence and
co-operation of aircraft saved the very frequent use of cavalry patrols
and detailed supports." The Royal Flying Corps was an important factor
in helping the British Expeditionary Force to escape von Kluck's nearly
successful efforts to secure another and a British Sedan.

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. m