In the battlefield north of the Somme, the British retired slowly until they were safely behind the Ancre River, which figured so prominently in the battle of the Somme in 1916. Taking Albert, an important British base, the Germans tried desperately to push beyond and reach the railroad which runs along the lower Ancre from Amiens to Albert. Failing in this, they struck heavily in the angle between the Somme and the Ancre in order to flank the line north of Albert from the high ground north-east of Corbie. Here also they met with defeat, so that from Beaumont-Hamel southward the Allied line became stationary. [Sidenote: The situation of the Germans.] [Sidenote: To win peace the Germans must destroy an army.] At this point in the battle the Germans found themselves in this situation: from Montdidier westward the French lines were firmly established first along a series of small but well defined heights as far as Noyons and thence along the southern bank of the Oise as far as the lower forest of Coucy. This side of the wedge was firmly fixed and capable of great resistance. Moreover, to expend time and men in an attack on this front would mean a serious departure from the German plan, as success here would mean an advance toward Paris instead of toward the sea. And at this stage of the war, peace cannot be obtained by the capture of any city, even the French capital. The price of peace is the destruction of an army, either that of the British or that of the French. This can be accomplished only through reaching the sea at some central point such as Abbeville at the mouth of the Somme. Therefore, the German problem had of necessity to find its solution north of Montdidier--between that town and Albert. There is not much doubt that by concentrating sufficient artillery and by the expenditure of sufficient men, the German leaders would be able to push their way farther westward, even beyond Amiens. But as the wedge deepened it would gradually draw down to a point so that the ultimate situation would be that the German lines would form an acute angle, the vortex of which would be on the Somme at or west of Amiens, one side passing through Albert, or possibly through the village of Bucquoy, the other through Montdidier. Such a formation would mean positive disaster. It would be worth a quarter of a million men to the Allies to strike both north and south across the base of this angle and snuff it out. It would mean to Germany the loss of a mass of artillery and tens of thousands of men. And the Allies would not be slow to see this opportunity and strike. The German High Command, therefore, did not dare to take the chance with matters as they then were. [Sidenote: Necessary to advance north of the Somme.] [Sidenote: The defenses of the British northern wing.] [Sidenote: The fight for Vimy and Notre Dame de Lorette.]