The establishment of a solid German rampart extending from the Oise across the Laon hills, dipping to the outlying forts of the old Rheims defences, and then reaching across Champagne, through the Argonne, and around Verdun, to Metz, was to prove one of the great achievements of the war, a defiance through nearly four years of sacrifice. For a moment, at the end of the battle of the Marne, it seemed that such a possibility might be averted. Conneau’s 2nd Cavalry Corps, the 18th Corps, and the 53rd and 69th Reserve Divisions had all passed the Aisne, between Bourg and Berry-au-Bac, on September 14. Conneau now found himself supporting a frontal attack of d’Espérey’s 18th Corps and reserves upon the abrupt cliffs by which the Aisne hills fall to the flats of Champagne, the Craonne plateau. A force from Lorraine under General von Heeringen was to be brought into this vital sector, between Kluck and Bülow; meanwhile, the connection was uncertain. While, a little farther west, Sir Douglas Haig was boldly reaching up to the Chemin des Dames, d’Espérey sent Conneau north-eastward as far as Sissonne; and thence one of his divisions was ordered to take in reverse the German troops posted above Craonne. Success seemed assured, when the 18th Corps and the reserve divisions were beaten back; and Conneau, fearing to be isolated on the north of the river, recrossed it. All the energy of General Maud’huy was needed to preserve a foothold on the right bank. Within a fortnight, the long deadlock of trench warfare had begun, and a new phase of the war had opened in the north-west.