In order that the German army might continue its march to the sea then, it was necessary that the line north of the Somme should advance, synchronizing its movement with the point of the wedge along the river.  Thus only would the wedge be sufficiently wide to avoid disaster.  But the entire northern wing of the British army was guarded by Vimy Ridge and the heights of Notre Dame de Lorette.  It was impossible that the advance could be made, leaving these positions directly on the flank.  The combination of these two heights forms a huge semicircle concave toward the south.  The British batteries posted on these heights could continue to rake the German advancing troops in flank and rear with most destructive effect.  Therefore, after the fighting in the south came to a halt, the Germans undertook to open the way by forcing these two positions.  Using seven divisions—­about 90,000 men—­the Germans attacked on a front not exceeding ten miles from Arleux to Fampoux on the Scarpe.  The attack continued for two days, but was an absolute failure.  The German advance had to be made down the slopes of one hill, across a stretch of flat, open valley, and up the sides of another.  Down in the valley were the British outpost positions which were overwhelmed and driven in.  But in attempting to cross the valley floor the Germans literally withered under machine gun and rifle fire.  At the end of two days’ fighting, during which the greater part of these divisions were cut to pieces, the attack had to be abandoned.  The fighting then from Lens southward to the Avre came to an end with the Germans completely halted.  The first definite stage of the decisive battle of the war was thus concluded.

[Sidenote:  The attack about Bucquoy.]

[Sidenote:  Considerable initial successes.]

[Sidenote:  A stand at the edge of the Forest of Nieppe.]

[Sidenote:  The Germans take Messines Ridge.]

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