General Franchet d’Espérey, who had been brigadier in 1908, divisional commander in 1912, a gallant and energetic officer now fifty-eight years of age, successful with the 1st Corps at Dinant and St. Gerard in Belgium, and in the important battle of Guise, had, on September 3, succeeded Lanrezac at the head of the largest of the French armies, the 5th. Its task——in touch with Foch on the right, and with the British, through Conneau’s cavalry corps, on the left——was to press north toward Montmirail, against Kluck’s left (III and IX Corps, and Richthofen’s cavalry divisions) and the right wing of Bülow (VII Corps and X Reserve Corps). In later stages of the war, the junction of two armies often showed itself to be a point of weakness to be aimed at. With four active corps and three divisions of reserves in hand, d’Espérey had, even before the German withdrawal began, a considerable advantage——indicating Joffre’s intention that it should be the second great arm of his offensive, that which should make the chief frontal attack. On the other hand, the enemy held strong positions along the Grand Morin, and, behind this, along the Vauchamps–Montmirail ridge of the Petit Morin. During their retreat the Allies had used the opportunity offered by the valleys of the Marne and its tributaries for delaying actions; these streams were now so many obstacles across their path. The first French movement, on September 6, was powerfully resisted. On the left, the cavalry occupied Courtacon.[63] At the centre, the 18th and 3rd Corps co-operating (prophetic combination——Maud’huy, Mangin, and Petain!), the villages of Montceaux-les-Provins and Courgivaux, on the highroad from Paris to Nancy, which was, as it were, the base of the whole battlefield, were taken by assault. On the right, the 1st Corps was stopped throughout the forenoon before Chatillon-sur-Morin by the X Reserve Corps. D’Espérey detached a division, with artillery, to make a wide detour and to fall, through the Wood of La Noue, upon the German defences east of Esternay. Thus threatened, the enemy gave way; and the market-town of Esternay was occupied early on the following morning. The 10th Corps continued the line toward the north-east, after suffering rather heavy losses beyond Sezanne.