On the right, Nieppe and Steenwerk had to be evacuated. The German advance to the south of Armentières becoming more pronounced, the British straightened their front, to avoid too sharp a salient, and fell back to the Messines-Wytschaete Crest. On the 12th the fighting continued furiously. Advancing along the Lille-Hazebrouck railway, the Germans reached the outskirts of Nieppe Forest. South-west of Merville they captured Calonne, and, further north, approached Bailleul. North of the Lys, under pressure of Von Arnim's army, the Messines-Wytschaete Crest, with the wood and village of Ploegsteert, had to be abandoned. The British line was withdrawn to Neuve-Eglise and Wulverghem. In these few days the gains of the Allied offensive of the last five months of 1917 were lost. The 13th marked the culminating point of the battle in the central sector. Foch made his dispositions promptly, and French reinforcements were despatched to the critical points. Von Bernhardi crossed the Clarence at Robecq on the 13th. On the same day Von Gallwitz made a strong push northwards between Hazebrouck and Bailleul, with the object of outflanking the line of the Flanders Hills, already attacked on the east and north-east by the IVth Army (Von Arnim). Battles were fought south of Meteren, at Merris, Vieux-Berquin and on the eastern outskirts of Nieppe Forest. To the east of Bailleul, Neuve-Eglise (an important cross-road) was fiercely disputed. After changing hands many times on the 14th, it was finally abandoned the same night. The loss of Neuve-Eglise led to that of Wulverghem, and the British were forced to fall back to the eastern slopes of Kemmel Hill, the first high point in the chain of hills called the Heights or Hills of Flanders. From east to west this chain consists of Rouge Hill (flanked on the north-east by Scherpenberg), Vidaigne Hill, Noir Hill, Cats Hill, and lastly by the western bastion of Cassel. After taking Neuve-Eglise on the night of the 14th, the Germans decided on a fresh and still more powerful effort. Three picked divisions were hurled against the hills of Lille and Ravetsberg, to the east of Bailleul, which fell. The Germans entered Bailleul, pushing on thence to Meteren, which they also captured. The next day they tried to develop this success, but instead of the exhausted British, the Germans now found themselves faced by fresh French troops. In three days (April 12--14) Pétain had brought up without a hitch five French divisions and one cavalry corps, which stayed the German rush at the foot of the hills. [Illustration: ROUGE HILL, SEEN FROM SCHERPENBERG HILL] On April 16 the Germans made their first attempt to turn the Flanders Hills from the south-west in the direction of Hazebrouck. The French 133rd Infantry Division (Valentin), supported by the British 34th Division, vigorously repulsed the attack.