84th and 88th Territorial divisions, to protect French communications. The French advanced on 22 September, on a line from Lassigny northwards to Roye and Chaulnes around the German flank but met the German II Corps, which had arrived on the night of on the right flank of the IX Reserve Corps. Despite the four divisions of the II Cavalry Corps (General Georg von der Marwitz), the Germans were pushed back to a line from Ribécourt to Lassigny and Roye, which menaced German communications through Ham and St. Quentin. On 24 September, the French were attacked by the XVIII Corps as it arrived from Reims, which forced back the French IV Corps at Roye on the right flank. To the north, the French reached Péronne and formed a bridgehead on the east bank of the Somme, only for the German XIV Reserve Corps to reach Bapaume to the north on 26 September. The offensive capacity of the Second Army was exhausted and defensive positions were occupied, while Joffre sent four more corps to reinforce. Over the next week, the northern flank of the Second Army moved further north and on 29 September, a (General Louis de Maud'huy) was formed, to control the northern corps of the Second Army as they assembled near Arras. Battle of Albert, 25–29 September On 21 September, Falkenhayn decided to concentrate the 6th Army near Amiens, to attack westwards to the coast and then envelop the French northern flank south of the Somme. The offensive by the French Second Army, forced Falkenhayn to divert the XXI and I Bavarian Corps as soon as they arrived, to extend the front northwards from Chaulnes to Péronne on 24 September and drive the French back over the Somme. On 26 September, the French Second Army dug in on a line from Lassigny to Roye and Bray-sur-Somme; German cavalry moved north to enable the II Bavarian Corps to occupy the ground north of the Somme. On 27 September, the German II Cavalry Corps drove back the 61st and 62nd Reserve divisions (General Joseph Brugère, who had replaced General Albert d'Amade), to clear the front for the XIV Reserve Corps and link with the right flank of the II Bavarian Corps. The French began to assemble at Arras and Maud'huy found that instead of making another attempt to get round the German flank, the subdivision was menaced by a German offensive. The