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.