Allusion has been made to the great bend which occurs in the course of the River Somme. It is indeed a geographical circumstance which must be borne in mind, if the phraseology current at this epoch in the war is to be clearly comprehended.
The river flows in an almost due northerly direction from the neighbourhood of Roye as far as Péronne, and then bends quite sharply, at that locality, in a western direction, past Bray, Corbie and Amiens, towards the sea, beyond Abbeville. In the story of the fighting of the period from March to August we have been concerned only with that portion of the river valley which ran parallel to our line of advance; but interest will henceforth focus itself largely upon that other reach of the Somme which runs on a north and south line, upstream, from the town of Péronne.
This latter stretch of the river lies squarely athwart the direction in which the Corps had been advancing, and the obstacle to that advance which the river would presently constitute was continued in a northerly direction from Péronne by an unfinished work of a great canalization scheme to be called the "Canal du Nord." This canal was already wide and deep, and formed a tactical obstacle of some significance, for the excavations incidental to this project had been almost completed before the war.
The "line of the Somme," as it was understood in the tactical discussions of the period now to be dealt with, meant, in short, the line formed by that part of the river which lay upstream (i.e., to the south of Péronne), and the continuation northwards of that line by the Canal du Nord. Both features being military obstacles, they and the highlands to the east of them together afforded an eminently suitable continuous line on which the enemy might, if he were permitted to do so, establish himself in a defensive attitude in order to bar our eastward progress.
The autumn was upon us; not more than another eight or nine weeks of campaigning weather could be relied upon. A quite definite possibility existed that the enemy might be able to put forth so powerful an effort to contest our further advance, inch by inch, that he would gain sufficient time to prepare the line of the Somme for a stout defence, and hold us up until the arrival of winter compelled a suspension of large operations.
There were at that time, indeed, some who contended that as we had apparently succeeded in putting an end to the German offensive we should rest content with the year's work; that our soundest strategy would be to permit the enemy to take up such a line of defence; and then quietly to wait over the winter until 1919 for the full development of the American effort, now only in its inception.
So far, the enemy had given no indication of any readiness to undertake a precipitate withdrawal from the great bend west of the Somme. On the contrary, his resistance had stiffened to such an extent that little further progress was to be hoped for from the methods of open warfare which I had employed since August 8th.
If, however, another powerful blow could be delivered, to be followed by energetic exploitation, it was quite possible that the enemy might be hustled across the Somme, that this might be achieved at such a rate that I could gain a firm footing on the east bank, and that thereby the value to him of the line of the Somme, as a winter defence, might be destroyed.
This was the very project on which I now embarked. The First Division was in Corps Reserve, had rested and was fresh. The 32nd Division had only just come into the line. By handing over a substantial sector to the French, my frontage south of the Somme was about to be shortened to 7,000 yards, a very suitable front for a deliberate attack by two Divisions.