It has been considered one of the chief advantages of giving a concentric direction to forces, that is, operating from the circumference of a circle towards the centre, that the further the forces advance, the nearer they approach to each other; the fact is true, but the supposed advantage is not; for the tendency to union is going on equally on both sides; consequently, the equilibrium is not disturbed. It is the same in the dispersion of force by eccentric movements. But another and a real advantage is, that forces operating on converging lines direct their action towards a _common point_, those operating on diverging lines do not.—Now what are the effects of the action in the two cases? Here we must separate tactics from strategy. We shall not push the analysis too far, and therefore confine ourselves to the following points as the advantages of the action in tactics. 1. A cross fire, or, at least, an increased effect of fire, as soon as all is brought within a certain range. 2. Attack of one and the same point from several sides. 3. 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.