Here we must keep in view, above all things, the principle with which we commenced, that forces destined to operate in rear cannot be used in front; that, therefore, the action against the rear or flanks is not an increase of force in itself; it is only to be regarded as a more powerful application (or employment) of the same; increasing the degree of success in prospect, but also increasing the degree of risk.
Every opposition offered with the sword which is not of a direct and simple nature, has a tendency to raise the result at the cost of its certainty. An operation against the enemy’s flank, whether with one compact force, or with separate bodies converging from several quarters, belongs to this category.
But now, if cutting off the enemy’s retreat is not to be a mere demonstration, but is seriously intended, the real solution is a decisive battle, or, at least, the conjunction of all the conditions for the same; and just in this solution we find again the two elements above-mentioned—the greater result and the greater danger. Therefore, if a general is to stand justified in adopting this method of action, his reasons must be favourable conditions.
In this method of resistance we must distinguish the two forms already mentioned. The first is, if a general with his whole force intends to attack the enemy in rear, either from a position taken up on the flank for that purpose, or by a formal turning movement; the second is, if he divides his forces, and, by an enveloping position with one part, threatens the enemy’s rear, with the other part his front.
The result is intensified in both cases alike, that is—either there is a real interception of the retreat, and consequently the enemy’s army taken prisoners, or the greater part scattered, or there may be a long and hasty retreat of the enemy’s force to escape the danger.
But the intensified risk is different in the two cases.