The operative corner was this group of armies before Namur on the Sambre and Meuse, the 4th French Army under Langle, the 5th French Army under Lanrezac, the British contingent under French.
We know from what has been written above in this book that it is the whole business of an operative corner to "take on" superior numbers, and to hold them as well as possible, even though compelled to retreat, until the manœuvring masses can swing and come up in aid, and so pin the enemy.
We further know from what has gone before that the whole crux of this manœuvre lies in the power of the operative corner to stand the shock.
It was the business of the French in this operative corner before Namur and of their British Allies there to await and, if possible, to withstand by a careful choice of position the first shock of enemies who would certainly be numerically superior. It was the whole business of the German commanders to make the shock overwhelming, in order that the operative corner should be pounded to pieces, or should be surrounded and annihilated before the manœuvring masses could swing up in aid. Should this destruction of the operative corner take place before the manœuvring masses behind it could swing, the campaign in the West was lost to the Allies, and the Germans pouring in between the still separated corners of the square were the masters for good.
It behoves us, therefore, if we desire to understand the campaign, to grasp how this operative corner stood, upon what defences it relied, in what force it was, what numbers it thought were coming against it, and what numbers were, as a fact, coming against it.
To get all this clear, it is best to begin with a diagram.
Suppose two lines perpendicular one to the other, and therefore forming a right angle, AB and BC. Suppose at their junction, B, a considerable zone or segment, SSS, of a circle, as shaded in the following diagram. Supposing the line AB to be protected along the outer half of it, AK, by no natural obstacle—the state of affairs which I have represented by a dotted line αγ; but suppose the second half of it, KB, should be protected by a natural obstacle, though not a very formidable one—such as I have represented by the continuous line γβ. Supposing the perpendicular line BC to be protected by a really formidable natural obstacle βδ, and supposing the shaded segment of the circle at B to represent a fortified zone (1) accessible to any one within the angle KBC, as from the arrow M; (2) inaccessible (until it was captured or forced) to any one coming from outside the angle, as from the arrows NNN; (3) containing within itself, protected by its ring of fortifications, passages, PP, for traversing the two natural obstacles, γβ and βδ, which meet at the point β.
Sketch 38.
There you have the elements of the position in which the advance corner of the great French square was situated just before it took the shock of the main German armies. The two lines AB and BC are the French and British armies lying behind the Sambre, γβ, and the Middle Meuse, βδ, respectively; but the line of the Sambre ceases to protect eastward along the dotted line αγ beyond the point up to which the river forms a natural obstacle, while from K to B the line is protected by the river Sambre itself. The more formidable obstacle, βδ, represents the great trench or ravine of the Meuse which stretches south from Namur. The town of Namur itself is at B, the junction of the two rivers; and the fortified zone, SSS, is the ring of forts lying far out all round Namur; while the passages, PP, over the obstacles contained within that fortified zone, and accessible to the people inside the angle from M, but not to the people outside the angle from NNN, are the bridges across both the Sambre and the Meuse at Namur.