This strategic conception, which I shall now describe, and which (in a diagram it is put far too simply) underlies the whole of the complicated movements whereby the French staved off disaster in the first weeks of the war, is one whose whole object it is to permit the inferior number to bring up a _locally_ superior weight against a _generally_ superior enemy in the decisive time and at the decisive place. Let us suppose that a general commanding _twelve_ large units--say, twelve army corps--knows that he is in danger of being attacked by an enemy commanding no less than _sixteen_ similar units. Let us call the forces of the first or weaker general "White," and those of the second or stronger general "Black." It is manifest that if White were merely to deploy his line and await the advance of Black thus, [Illustration: Sketch 21.] he would be outflanked and beaten; or, in the alternative, Black might mass men against White's centre and pierce it, for Black is vastly superior to White in numbers. White, therefore, must adopt some special disposition in order to avoid immediate defeat. Of such special dispositions one among many is the French Open Strategic Square. This disposition is as follows:-- White arranges his twelve units into four quarters of three each, and places one quarter at each corner of a square thus:-- [Illustration: Sketch 22.] We will give them titles, and call them A, B, C, and D. If, as is most generally the case in a defensive campaign at its opening, White cannot be certain from which exact direction the main blow is coming, he may yet know that it is coming from some one general direction, from one sector of the compass at least, and he arranges his square to face towards that sector. For instance, in the above diagram, he may not know whether the blow is coming from the precise direction 1, or 2, or 3, but he knows that it is coming somewhere within the sector XY. Then he will draw up his square so that its various bodies all face towards the average direction from which the blow may come. The SIZE of his square--which is of great importance to the result--he makes as restricted as possible, _subject to two prime conditions_. These conditions are:--