At nightfall on August 22, 1914, Charleroi burst into flames. A dread and significant glow fell upon the sky. Absent were the usual intermittent flare of blast furnaces. The greater part of Charleroi had become a heap of ruins. Those of its citizens still alive cowered in holes or corners for shelter.
The battle of Charleroi went on throughout the night. Early on the morning of Sunday, August 23, 1914, Von Hausen swept down through the gap between the armies of Von Bülow and the Duke of Württemberg. He crossed the Meuse, drove from before him the French detachments watching it, and advanced to attack the rear of the French right.
Von Hausen took the French at Charleroi completely by surprise. At the moment they could comprehend neither where he came from nor the measure of his strength. But he was in army force.
The French were compelled to withdraw their right from Charleroi. Von Hausen seized the advantage to hurl his forces upon their rear, while Von Bülow thundered in assault more vigorously than ever on the French front. A powerful force was hurled upon them from an unexpected direction. Presently the retreat of the French Fifth Army was threatened by the two Saxon corps of Von Hausen's army, pressing on the French right flank and rear. In this emergency the retirement of the French Fifth Army appears to have been undertaken with spontaneous realization of utmost danger. It gave way before the attacks of Von Bülow and Von Hausen to move southward, leaving their British left wing without information of defeat.
On Friday, August 21, 1914, the British force began to take position on the French left, forming the line Binche-Mons-Condé. When finally concentrated it comprised the First and Second Army Corps, and General Allenby's cavalry division. The regiments forming the cavalry division were the Second Dragoon Guards, Ninth Lancers, Fourth Hussars, Sixth Dragoon Guards, with a contingent of the Household Guards. The First Army Corps was given the right of the line from Binche to Mons. It was commanded by Sir Douglas Haig. He was a cavalry officer like the commander in chief, and a comparatively young man for such a responsibility, but had seen active service with credit. His corps was comprised of six guards' battalions. The First Black Watch, Second Munster Fusiliers, The Royal Sussex, North Lancashire, Northamptons, Second King's Royal Rifles, Third West Surreys, The South Wales Borderers, Gloucesters, First Welsh Regiment, Highland Light Infantry, Connaught Rangers, Liverpools, South Staffords, Berkshires, and First King's Royal Rifles. The First Irish Guards went into action for the first time in its history.