- The cutting off the retreat.
The interception of a retreat may be also conceived strategically, but then it is plainly much more difficult, because great spaces are not easily blocked. The attack upon one and the same body from several quarters is generally more effectual and decisive, the smaller this body is, the nearer it approaches to the lowest limit—that of a single combatant. An army can easily give battle on several sides, a division less easily, a battalion only when formed in mass, a single man not at all. Now strategy, in its province, deals with large masses of men, extensive spaces, and considerable duration of time; with tactics, it is the reverse. From this follows that the attack from several sides in strategy cannot have the same results as in tactics.
The effect of fire does not come within the scope of strategy; but in its place there is something else. It is that tottering of the base which every army feels when there is a victorious enemy in its rear, whether near or far off.
It is, therefore, certain that the concentric action of forces has an advantage in this way, that the action or effect against a is at the same time one against b, without its force against a being diminished, and that the action against b is likewise action against a. The whole, therefore, is not a + b, but something more; and this advantage is produced both in tactics and strategy, although somewhat differently in each.
Now what is there in the eccentric or divergent action of forces to oppose to this advantage? Plainly the advantage of having the forces in greater proximity to each other, and the moving on interior lines . It is unnecessary to demonstrate how this can become such a multiplier of forces that the assailant cannot encounter the advantage it gives his opponent unless he has a great superiority of force.—When once the defensive has adopted the principle of movement (movement which