By 20 August, Lanrezac's Fifth Army had begun to concentrate on a 40-km front along the Sambre, centred on Charleroi and extending east to the Belgian fortress of Namur. On his left, the Cavalry Corps of General Sordet linked the Fifth Army with the British Expeditionary Force at Mons. Lanrezac's army of 15 divisions, weakened by the transfer of troops to Lorraine, was confronted by the 38 German divisions from the Second Army (General Karl von Bülow) and Third Army moving south-west.