Two interior lines of operation, possessing the means of reciprocally sustaining each other, and destined to face, at a certain distance, two exterior lines of an ene my, must avoid being encompassed by him within a space so contracted as to enable his divisions to act simultaneously ; and they must equally avoid the op posite ext•eme.—that of pushing their operations too far asunder,—because the enemy would have time to crush that division which has been weakened to I tin force the other, and might then make such progress and conquests as might become irresistiole.
Let us suppose an at my, equal in fence to its oppo nent, but acting in two or three isolated corps, upon lines of operation having an exterior direction, while the enemy operates in a body upon a single line ; the army so Givided will never gain any real a, vantage, unless the several corps can attach: simultaneow,ly ; because the enemy will always have it in his power to oppose double or triple the numbei, of troops to each of their separate corps. 1-1,:nce, two interior lines are advant gc ous, bt,..ausc they can concentrate their Laces at w ill, and with rapidity than the enemy, and consequently d, ubie their numerical strength For the same reason, single lines, such as have their parts muted, and can mutually sustain each other, are to be pry lerred.t From these observations we may deduce the gene ral principle upon which all combinations in war ought to be constructed. This principle consists in congre gating upon the most important point of a line of ope rations, Or of a field of battle, a number of forces supe rior to that of the enemy. To effect this on lines of operation, marches and strategical movements must be employed ; and on fields of battle, we must adopt proper manoeuvres, or select judicious modes of attack.
As the principles we have just laid down respecting lines of operation are also applicable to the manoeuvres on a field of battle, we shall have occasion to illus trate them still farther in a subsequent section. Mean while, we shall only observe that lines of operations have their keys as well as fields of battle ; upon these lines there are decisive strategical points, which com mand the remainder, and have the same influence on operations, as certain points of ground have on battles.
We have already had occasion to lay down some gene ral rules on the subject of positions, while treating of the principles of cast' ametation. A camp, however, may be in itself exceedingly strong, and yet totally useless with respect to the object in view. The science of po sitions, on the other hand, exhibits the principles ap plicable to the choice of a camp the best adapted, ac cording to circumstances, to the proposed object.
In the case of an offensive war, combined with a sur prise, there is no great difficulty in chusing positions.
An attack in these circumstances presupposes superi ority, and all the art, therefore, which is necessary, con sists in the ordinary precautions for the safety and sup ply of the troops, which are determined by the disposi tions of the enemy ; and with respect to positions, there is almost nothing farther required, than the art of se lecting the best routes.
But the art of positions becomes much more difficult and important, when we have to act offensively against an enemy who is fully prepared. It is then necessary to determine the best means by which we may be en abled to break into his parallel. 1. If this is to be ef fected by a battle, the art of positions is of less impor tance ; because, in that case, we must attack him in the position which he has chosen ; or, if it be too strong, we must endeavour to force him out of it by skilful manoeuvres. 2. If it is to be done by cutting off his forage and supplies, we must establish ourselves in a strong position, near the enemy—if possible, quite on his flank, but, at all events, somewhat obliquely, in or der that our light troops may get into his rear, and in tercept his convoys. No pains should be spared in pro curing intelligence respecting his foraging parties, which must be constantly annoyed by all possible means. At the same time, we must beware of exposing our own parallel, which should always be secured by for tresses, or posts, or detached corps. Or we should en deavour to out-flank him in his position, by occupying tenable places, or positions for separate corps on his flanks, to enable us to get into his rear, and attack all his convoys and foraging parties. 3. If our purpose is to be executed by means of detachments, we must previously observe upon what grounds the effect of a detachment rests. So long as our main army remains on the spot, it is presumed that the enemy cannot move ; for otherwise the position must have been ill chosen. A corps is then detached from the army, as strong as is required and can be spared, in order to execute some enterprise injurious to the enemy. This enterprise may consist either in a particular blow, such as the attack of a post, the cutting off a convoy, the destruction of a magazine, &c.; or in preparation for some blow, which is to be executed afterwards by the whole army ; such as the investment of a fortress, throw ing bridges over a river which the army is to pass, oc cupying the entrance and debouche of a defile, &c. It is not always necessary that the corps should actually execute the enterprise, but only that it should be so placed as to be able to execute it, if the enemy takes no measures to oppose it.