About the middle of August, 1914, General Joffre, assigned to the British Expeditionary Force, commanded by Sir John French, the task of holding Mons against the powerful German advance. The British force formed the left wing of the line of front that stretched for some two hundred miles close to the Belgian frontier. Extending from Arras through the colliery towns of Mons and Charleroi, the extreme western front of the armies was held by General D'Amade at Arras, with about 40,000 reserve territorial troops; by General French, with 80,000 British regulars, at Mons; by the Fifth French Army of 200,000 first-line troops, under General Lanrezac, near Charleroi; and by a force of 25,000 Belgian troops at Namur. The total Allied troops in this field of battle were thus about 345,000 men. Opposed to them, on the north, were about 700,000 German troops, General von Kluck farthest to the west, Generals von Buelow and von Hausen around the Belgian fortress of Namur, Grand Duke Albrecht of Wuerttemberg in the neighborhood of Maubeuge, and finally, on the extreme left of the German line, the Army of the Moselle, under Crown Prince Wilhelm. The position of the Allied armies was based on the resisting power of Namur. It was expected that Namur would delay the German advance as long as Liege had done. Then the French line of frontier fortresses--Lille, with its half-finished defenses; Maubeuge, with strong forts and a large garrison; and other strongholds--would form a still more useful system of fortified points for the Allies. The German staff, however, had other plans. At Liege they had rashly endeavored to storm a strong fortress by a massed infantry attack, which had failed disastrously until their new Krupp siege guns had been brought up. These quickly demolished the defenses. These siege guns, therefore, which had thus fully demonstrated their value against fortifications soon brought about the total defeat of the French offensive, and compelled the Allies to retreat from Belgium and northern France. The Germans lost no time in investing Namur, and on Saturday, as noted above, August 22, 1914, the fortress fell into the invaders' hands. On the same day, August 22, 1914, the Fifth French Army, under the lead of General Lanrezac, was enduring the double stress of Von Buelow's army thundering against its front, and Von Hausen's two army corps pressing hard upon its right flank and rear, threatening its line of retreat. Against such terrific odds the French line at Dinant and Givet broke, exposing the flank and rear of the whole army; and by the evening of that day, August 22, the passages of the River Sambre, near Charleroi, had been forced, and the Fifth Army was falling back, contesting every mile of the ground with desperate rear-guard action. The British, meanwhile, defending the Mons position, were in grave danger of being cut off, enveloped, and destroyed.