Army between the Oise and the Marne, occupying the
Marne crossings west of Chateau-Thierry, and the Second Army between the
Marne and the Seine, occupying the Seine crossings from Nogent to Mery.
This led, says von Kluck, to 'the difficult backwards wheel' of the
First Army, and to what he calls 'the important events that occurred
during the second week of September'--events known to history as the
battle of the Marne. Von Kluck allowed the original movements ordered
for the 5th to be carried out, and, he says, 'the conclusion of this
advance marked the culminating point of the operations of the First
Army'. On this same day General Joffre told Sir John French that he
intended to take the offensive forthwith as the conditions seemed
favourable, and on the morning of the 6th this offensive opened.

The main work of the Royal Flying Corps throughout the days of the
retreat was reconnaissance, and enough has been said of their reports to
show that Sir John French was well served by his new arm. He had been
warned before the battle of Mons, not only of the heavy movement on his
front but of the enveloping attempt on his flank, and throughout the
retreat he was punctually informed of von Kluck's enveloping efforts.
The change of direction made on the 31st of August was immediately seen
and reported. Von Kluck's renewed pursuit of the British on the two
following days did not escape observation. Finally, the German swerve to
the left on the 3rd of September was closely followed from the air.
These are the main conclusions that come from a study of the air reports
of those days. General Headquarters were perhaps at first a little shy
of trusting the air reports, but they realized their value during the
retreat, and paid more and more attention to them--an attention which
found practical results in the operation orders issued. The Royal Flying
Corps played their part in helping the British army to escape. Further,
they were making themselves, and were improving in skill every day. The
lessons learned on the retreat from Mons bore their full fruit at a
later period, when the officers of the original squadrons held the
command of those Flying Corps units which operated in the mobile
campaigns of distant theatres of the war.

Their work during the retreat was done under difficulties. There were
alarms at Compiegne of Uhlans seen in the vicinity of the aerodrome, and
a guard was provided from the Camerons. Major B. H. Barrington-Ke