But the Germans were by no means ready to acknowledge defeat. The Lens-Arras sector had to be cleared up. The attack from the south, crystallizing about Bucquoy, and from the east both having broken down, there remained but to attack from the north. Utilizing to the utmost the advantages of the great railroad system which parallels this front, connecting in a single chain all of their great advance bases, the Germans effected a heavy concentration at Lille, and, using about twenty divisions (which were afterward increased to thirty), struck the British line between Givenchy--just north of La Bassee--and Warneton on the Lys River. The initial successes were considerable. The Germans penetrated to a maximum depth of more than four miles in the centre, although on both right and left the line held fast. North of Armentieres, however, the British line gave ground, which enabled the Germans to pocket this city and to capture it on the second day of the attack. On the succeeding days, the British centre continued to give way until the edge of the Forest of Nieppe was reached. The German position at this point in the attack became practically untenable. The northern side of this wedge was lined with heights from which the British artillery was pouring a devastating plunging fire. These heights, beginning farther east, began with the famous Messines-Wytschaete Ridge and extended due west through Kemmel to Cassel. Moreover, in falling back the British pivoted on Messines, which left this strong bastion from which to strike out against the very heart of the salient. Accordingly, to remove this danger the German leaders swung the attack north against the Messines Ridge. After days of fighting in which Bailleul was taken and the foot of the Kemmel series of hills was reached, the Messines Ridge was taken in reverse and the British line was withdrawn until it passed over the ridge just north of Wytschaete. Still pressing on the north, the Germans attacked the Kemmel position, but the British, now reinforced by the French, threw the attacks back as rapidly as they formed. Failing here and at the centre in Nieppe Forest, still another attack was delivered, this time against the southern side of the wedge from Givenchy to St. Venant. The first two days of this fighting was also disastrous to the Germans who were entirely unable to dent the British positions. In brief, the Germans were then enclosed in a huge semicircle about fifteen miles in diameter. All parts of the area enclosed were subject to artillery fire from three sides and the Germans were striking first on one side then on the other in frantic efforts to break the Allies' grip--and giving no indication of sufficient power to succeed. [Sidenote: Objectives of the Germans in the North.] [Sidenote: The British gradually retire about Ypres.]