3. That the relation of the lines of communication may also have a favourable influence on the form of combat; and
4. That the general influence of the country is advantageous.
For the relation of the lines of communication has an influence not only upon the possibility or impossibility of passing by a position or of cutting off the enemy’s supplies, but also on the whole course of the battle. An oblique line of retreat facilitates a tactical turning movement on the part of the assailant, and paralyses our own tactical movements during the battle. But an oblique position in relation to the lines of communication is often not the fault of tactics but a consequence of a defective strategic point; it is, for example, not to be avoided when the road changes direction in the vicinity of the position (Borodino, 1812); the assailant is then in such a position that he can turn our line without deviating from, his own perpendicular disposition.
Further, the aggressor has much greater freedom for tactical movement if he commands several roads for his retreat whilst we are limited to one. In such cases the tactical skill of the defensive will be exerted in vain to overcome the disadvantageous influence resulting from the strategic relations.
Lastly as regards the fourth point, such a disadvantageous general influence may predominate in the other characteristics of ground, that the most careful choice, and the best use of tactical means, can do nothing to combat them. Under such circumstances the chief points are as follows:
1. The defensive must particularly seek for the advantage of being able to overlook his adversary, so that he may be able swiftly to throw himself upon him inside the limits of his position. It is only when the local difficulties of approach combine with these two conditions that the ground is really favourable to the defensive.
On the other hand, those points which are under the influence of commanding ground are disadvantageous to him; also most positions in mountains (of which we shall speak more particularly in the chapters on mountain warfare). Further, positions which rest one flank on mountains, for such a position certainly makes the passing by more difficult, but facilitates a turning movement. Of the same kind are all positions which have a mountain immediately in their front, and generally all those which bear relation to the description of ground above specified.
As an example of the opposite of these disadvantageous properties, we shall only instance the case of a position which has a mountain in rear; from this so many advantages result that it may be assumed in general to be one of the most favourable of all positions for the defensive.
2. A country may correspond more or less to the character and composition of an army. A very numerous cavalry is a proper reason for seeking an open country. Want of this arm, perhaps also of artillery, while we have at command a courageous infantry inured to war, and acquainted with the country, make it advisable to take advantage of a difficult, close country.
We do not here enter into particulars respecting the tactical relation which the local features of a defensive position bear to the force which is to occupy it. We only speak of the total result, as that only is a strategic quantity.