On the morning of September 7, the air services of the 5th Army reported the commencement of Kluck’s retreat; and soon afterwards a corresponding movement of Bülow’s right was discovered to be going on behind a screen of cavalry and artillery, supported by some infantry elements. D’Espérey had no sooner ordered the piercing of this screen than news was brought in of the critical position of the neighbouring wing of Foch’s Army, the 42nd Division and the 9th Corps, through which Bülow’s X and Guard Corps were trying to break, from the St. Gond Marshes toward Sezanne. He at once diverted his 20th Division to threaten the western flank of this attack (which will be followed in the next section) about Villeneuve-lès-Charleville. Meanwhile, rapid progress was being made on the centre and left of the 5th Army. Between Esternay and Montmirail extend the close-set parklands called the Forest of Gault, with smaller woods outlying, a difficult country in which many groups of hungry German stragglers were picked up during the following days. Through this district, the 1st Corps and the left of the 10th, with General Valabrègue’s three divisions of reserves behind, beat their way; while, farther west, in the more open but broken fields between the Grand and the Petit Morin, the 18th and the 3rd Corps made six good miles, to the line Ferté Gaucher–Trefols. More than a thousand prisoners were taken during the day, with a few machine-guns and some abandoned stores. We have seen (pp. 124–5, 131) the British Expeditionary Force at the beginning of a like novel and exhilarating experience. Its five divisions, having seized Coulommiers on the night of September 6, had pressed on to the Petit Morin, and, from its junction with the Marne eastward to La Trétoire, where obstinate opposition was offered, had secured the crossings. D’Espérey’s left wing thus found its task lightened; and the 18th and 3rd Corps were ordered to sweep aside the remaining German rearguards, and to strike across the Petit Morin on either side of Montmirail. September 8 was thus a day rather of marching than fighting, except at Montmirail, on whose horse-shoe ridge the enemy held out for some hours.[64] In the evening, General Hache entered the picturesque town, and set up his quarters in the old château where Bülow’s Staff had been housed on the previous day. On the left, Maud’huy pushed the 18th Corps by Montolivet over the Petit Morin, and after a sharp action took the village of Marchais-en-Brie. On the right, the 1st Corps was checked at Courbetaux and Bergères, the German VII Corps having come into line; so that the 10th Corps, between Soigny and Corfelix, had to turn north-westward to its assistance. This was scarcely more than an eddy in the general stream of fortune. The moral effect of a happy manœuvre goes for much in the result. The British and d’Espérey’s men forgot all their sufferings and weariness in the spectacle of the enemy yielding. British aviators