General Mangin's troops meanwhile were encountering strong opposition as they forced their way forward into the wooded heights that constituted the outer bastion of the St. Gobain Forest. This operation, taken in conjunction with the advance of Generals Debeney and Gouraud on the flanks, rendered the position of the German forces holding the Laon salient increasingly dangerous. On October 12, 1918, General Mangin seized the greater part of the St. Gobain Massif. La Fère, the outpost to the north on the Oise, was also won. Laon, the last of the great natural obstacles forming the keystone of the German defenses in France, yielded without a fight. The British had now invested Douai, and the fall of that place was only a question of hours. All these important achievements were less spectacular than the great battle in Flanders which began on October 14, 1918, and was fought by the combined Belgian, French, and British troops under the command of King Albert. The whole Allied line advanced on an irregular front of about twenty-five miles from the region of Courtemarck to that of Courtrai, penetrating enemy positions six and seven miles. The British Second Army under General Sir Herbert Plumer captured the villages of Gulleghem and Heule and advanced as far as the outskirts of Courtrai, having taken nearly 4,000 prisoners and fifty guns. The Belgians and French bagged over 7,000 and eighty guns. In French Flanders the British carried their lines forward in the neighborhood of Haubourdin about three miles west of Lille, and farther south crossed the Haute Deule Canal and took a number of villages northeast of Lens. So fast were the Germans retreating that the British, French, and Belgian infantry in the center of the battle front had lost sight of them. The victory was especially memorable because it was a triumph for the gallant little Belgian army, which with the assistance of French and British had driven the despoilers of their country from a large territory which the Germans had occupied since the first days of the war. Moreover, they had gained in this battle such strong positions that the Germans must soon be forced to abandon the entire coast of Belgium.