Therefore, if on the one hand, the violence with which we wish to strike the blow prescribes the greatest concentration of force, so in like manner, on the other hand, we have to fear every undue excess as a real evil, because it entails a waste of power, and that in turn a deficiency of power at other points.
To distinguish these “centra gravitatis” in the enemy’s military power, to discern their spheres of action is, therefore, a supreme act of strategic judgment. We must constantly ask ourselves, what effect the advance or retreat of part of the forces on either side will produce on the rest.
We do not by this lay claim in any way to the discovery of a new method, we have only sought to explain the foundation of the method of all generals, in every age, in a manner which may place its connection with the nature of things in a clearer light.
How this conception of the centre of gravity of the enemy’s force affects the whole plan of the war, we shall consider in the last book, for that is the proper place for the subject, and we have only borrowed it from there to avoid leaving any break in the sequence of ideas. By the introduction of this view we have seen the motives which occasion a partition of forces in general. These consist fundamentally of two interests which are in opposition to each other; the one, the possession of territory strives to divide the forces; the other, the effort of force against the centre of gravity of the enemy’s military power, combines them again up to a certain point.
Thus it is that theatres of war or particular army regions originate. These are those boundaries of the area of the country and of the forces thereon distributed, within which every decision given by the principal force of such a region extends itself directly over the whole, and carries on the whole with it in its own direction. We say directly, because a decision on one theatre of war must naturally have also an influence more or less over those adjoining it.