the retreat from Mons, and the troops were
not well pleased when they were ordered to retire. But the retreat was
inevitable, and the most that the British could do was by rearguard
actions to put a brake upon the speed of the advancing enemy until such
time as they should be able to form up again in the Allied line and
assail him. Much depended on their power to gain information concerning
the movements of the enemy, so that they might know their own dangers
and opportunities. Von Kluck had at first no definite news of the
whereabouts of the British army. As late as the 20th of August the
German Supreme Command had issued a communication to the German armies
stating that 'a disembarkation of British Forces at Boulogne and their
employment from the direction of Lille must be taken into account. It is
the opinion here, however, that a landing on a big scale has not yet
taken place.' General von Zwehl, Commander of the Seventh Reserve Corps,
writing in September 1919, tells how the Germans had no reliable
information concerning the British expeditionary force. 'It was only on
the 22nd of August,' he says, 'that an English cavalry squadron was
heard of at Casteau, six miles north-east of Mons, and an aeroplane of
the English fifth flying squadron was shot down that had gone up from
Maubeuge. The presence of the English in front was thus established,
although nothing as regards their strength.' The first news that reached
General von Kluck of the presence of the British forces came to him from
a British, not from a German, aeroplane.

[Illustration: Map Illustrating Aerial Reconnaissance Area. 19th to 24th
Aug. 1914]

The first aerial reconnaissances by the Royal Flying Corps were carried
out on Wednesday, the 19th of August, by Captain P. B. Joubert de la
Ferte of No. 3 Squadron, in a Bleriot, and Lieutenant G. W. Mapplebeck
of No. 4 Squadron, in a B.E. They started at 9.30 a.m., and flew without
observers. Captain Joubert de la Ferte was to reconnoitre
Nivelles-Genappe in order to report what Belgian forces were in that
neighbourhood; Lieutenant Mapplebeck was to find out whether enemy
cavalry were still in force in the neighbourhood of Gembloux. The
machines were to fly together as far as Nivelles, 'so that if one was
obliged to descend the other could report its whereabouts'. The machines
lost their way and lost each other. Lieutenant Mapplebeck eventually
found himself over a large town which he failed to recognize as