This timely reinforcement was at once sent off to the support of the Second Corps. * * * * * We now know how a small army of much-tried Britons barred the way through the La Bassée postern and stretched a thin line of valour and steel northwards towards the Lys. I have still to tell you how the twelve-mile gap between Armentières and Ypres was closed. While the Second Corps was forming up near Béthune, the trains carrying the Third Corps were running into St. Omer. As each unit arrived it set out for Hazebrouck, and on the 13th the whole force moved eastwards towards the line of the Armentières-Ypres road, with the object of reaching Armentières, from which it could threaten Lille. Gough's cavalry lay to the north, and French cavalry to the south. The French cavalry had already done much hard fighting. On 9th October it was discovered that German horsemen were holding the south bank of the Lys to the west of Estaires. They had covered the river crossings with machine guns, and had set up searchlights, which at night swept their broad beams along the northern bank. The French commander assembled his men at a point on the river where the current was very swift and the water deep. The Germans believed that the river could not be forded at this spot, and had not troubled to hold it strongly. At dusk a French trooper who was a good swimmer stripped, and, carrying with him one end of a light rope, plunged into the water and swam across the river. When he arrived on the south bank his comrades on the other side fastened a heavy rope to the end of the line which he was holding, and the dripping soldier hauled it across and tied it securely to the trunk of a tree. The other end of the rope was made fast in a similar way, and during the night, assisted by the rope, men and horses crossed the stream. At daybreak, when the Germans found that the French were on their bank of the river they retired rapidly towards Armentières.