At once there was precipitated a conception which governed not only the battle of the Marne, but the whole after-development of the war. There must be no more rash adventures on the east; from Belfort to Verdun, the front would be held defensively, with a minimum of strength, to fulfil the purpose for which its fortifications were built, and to protect the main forces, which would operate henceforth in the centre and west. The importance of the north-west coast, and the fact that Kluck was not approaching it, plainly suggested the creation of a new mass of manœuvre on this side to menace the German flank: this new body was Maunoury’s 6th Army. These two features of the Allied riposte——defence on the east, offence from the west——were to be permanent. The French centre must be strengthened to bear the impact of Bülow, the Saxons, and the Duke of Würtemberg. Foch’s Army, created to this end, to come in between those of d’Espérey (Lanrezac’s successor) and de Langle, had the further effect of preserving the full offensive strength of the 5th Army. For these purposes, large numbers of men had to be transferred from the east to the west and centre. Joffre at first hoped to stand on the Somme, and then on the Oise. But the new forces were not ready; the defence of the east was not secured; the British Army was momentarily out of action; Kluck threatened the Allied communications; the line was a hazardous zigzag. The Generalissimo would not again err on the side of premature attack. The pursuit was not an unbroken course of victory for the invaders. Before the Gap of Charmes, on August 24–26, Castlenau and Dubail administered the first great German set-back of the war. At the same time, the Prince Imperial received a severe check at Etain; and, although Smith-Dorrien’s stand at Le Cateau on August 26 disabled the British Force for some days, it did much to save the Allied left wing. On August 28, the German IV Army was sharply arrested at Novion Porcien; and next day took place the combats of Proyart and Dun-sur-Meuse, and the battle of Guise. In these and many lesser actions, the spirit of the armies was prepared for the hour when the issue should be fairly joined.