twenty-eight if the German Fourth and Fifth Armies in the centre are also included), he believed that only a few of these would come west of the Meuse, where he believed they could be held by the British and Belgians. French Third and Fourth Armies, on Lanrezac's right, were preparing to attack into the Ardennes in accordance with Plan XVII, and Joffre wanted Lanrezac's Fifth Army to attack the bulk of the German right wing on its west flank as—it was assumed—it attacked the left flank of French Fourth Army. Lanrezac, forbidden to retreat by Joffre, reported that he would be ready to attack by 20 August. Lanrezac began to move north on 19 August, leaving a gap between his army and Fourth Army on his right. Joffre believed (20 August) that Liège was still holding out (in fact the last of the Liège forts had fallen on 16 August and by 20 August Brussels had fallen and the Belgians were falling back on Antwerp), and hoped that Lanrezac would be able to link up with Namur, which was expected to hold out for even longer. On 20 August Gallwitz persuaded von Bulow (commander, German Second Army) to attack Lanrezac to pin down his army and prevent him marching to the relief of Namur. Battle of Charleroi Joffre's Instruction 13 mentioned that the Germans had thirteen or more corps in Belgium, of which eight were north of the Meuse. If these turned south then Lanrezac was to leave his position to the British and Belgians and attack into the Ardennes, as Joffre wrongly believed that a strong German thrust through Belgium would have left the German centre (in the Ardennes) weak. Lanrezac declined to attack as Joffre wished on 21 August as the BEF were not yet in position on his left. With the French Third and Fourth Armies now attacking into the Ardennes, Lanrezac also declined to send reinforcements to Namur, which he had been warned would not hold out. On 22 August Lanrezac attempted to drive the Germans across the Sambre and failed. Later that day the German Second Army attacked the French Fifth Army and forced bridgeheads across the Meuse. Within a fortnight, Joffre had sacked one of the French corps commanders—General Sauret of III Corps, who had disappeared during the battle, leaving the corps artillery commander to take charge—and three of the four division commanders involved.