There are two descriptions of cases in which the passage of a defile is attended with difficulty. I When the enemy is posted on the other side, and we march towards him. 2 Waen we are on the same side with the enemy, and our object is to place the defile between him and ourselves. In the first case, the enemy ;nay either he ,e.v 11 e of the point at which we wish to pass, and be prepared to dispute the pas sage ; or he may •• in doubt wit'i respect to the point, and we endeavour to p•ss u• p rc. ived. It must be observed, that a defile canons b • s rd to be p,ssed. trail the whole troops are through it, or, a least, until so many are placed. and in such ormir, on the opposite side, that the enemy cannot prevent the passage of the whole.
In the case of most defiles. the roads are already prepared. But rivers have generally t tis peculiarity, that the passage must first be prepared by torowing a bridge over them, which is commonly a bridge of boats or pontoons. But, in order to enable us to throw over Close hridges, atiLl to d.•fen I them, it is necessary to ti eve a ho ly of troops oil the other side. And as, i t almost all cas...s, the fire of our artillery, and some times even of our small aria can reach the opposite side, and thus cover the construction of the bridge, the passage, and the deploying of the troops, a river may often be passed, but any other defile seldom, by force.
In order to effect the passage of a river by force, it is necessary,-1. That we should have a convenient situation for constructing more than one bridge ; and hence the bank should neither be too high nor too low. 2. That we should have an advantageous position for the artillery, and also, if possible, for the small arms, so that they may have a cross fire at the place where the bridges are constructed. The heights, therefore, on the side from which we are to cross, must be more elevated than those on the opposite side ; at the place where the bridges are formed, the river should have a bend inwards ; and the river itself should not be too broad. 3. That there be no new defiles on the other side of the river, but a good free space where the troops can easily form under their fire, and then proceed to attack the enemy.
The following dispositions are then made for the passage. I. The artillery and troops are stationed at those points where they can act with most effect upon the opposite side, and, if possible, they should be placed behind breast-works. 2. Troops are sent over, partly for the purpose of constructing the bridge, and partly in order to throw up entrenchments before it, which must be the more strongly constructed and oc cupied, the less we can depend upon the effect of the fire from our own side for protecting the entrench ment, the bridge, and the deploying of the troops on the opposite side. These troops must get over by means of fords, boats, or rafts. In fording, the cavalry generally cross over, carrying the infantry behind them. The cavalry remain on the opposite side, if they have nothing to apprehend from the enemy's fire, and, under the fire of their own people, keep themselves ready to attack all that approach the entrenchment or the bridge itself. As soon as the bridge, and the works on the opposite side are completed, the troops commence the passage, in such order as circumstances require, rapidly, but without tno much haste. The order depends upon
the nature of the ground. If the country be level, and favourable for cavalry manoeuvres, the horse must pass first, in order to cover the passage of the infantry. If it he necessary to occupy an advantageous position with artillery, a corps of infantry, with a brigade of the park, takes the lead. The situation may be so favourable for the passage, that the troops, as soon as they arrive on the other side, can deploy and march forwards ; it frequently happens, however, that they must first place themselves in the entrenchment, and gradually advance and deploy as they receive reinforcements. 4. When the enemy perceives that the passage is certain, he generally re tires. If he does not, as soon as the requisite number of troops arrive, he must be attacked according to the na ture of the ground and of his position; and he must be beaten, otherwise we should be in a most perilous situation; and therefore such a passage must never be attempted without a moral certainty of being able to accomplish it.
In order to effect the passage of a river by strata gem, it is necessary, 1. To choose a position from whence we can speedily reach several places where a passage may be accomplished ; and in such a manner, that when the enemy places himself so as to oppose us at some of these points, he will be obliged to make a circuit before he can reach the others. 2. To make all kinds of feigned dispositions, and feigned movements. with the whole or a part of the army, in order to mis lead him. 3. Should he expose any part, we must en deavour to send over a corps of cavalry and infantry, with the articles necessary for forming an entrench ment, at such places where they can best effect a pas sage. 4. These must construct bridges, and entrench themselves as rapidly as possible, and, at the same time, occupy, as far as their force will permit, those places from which the debouche can be covered. 5. If these measures succeed, the army prepares for the passage, and the support of the corps. 6. When the dispositions have been so far completed, the army passes, after having previously occupied all those points, which can cover and secure the passage and the dcbouche. 7. As the troops anive, they must be so placed as to protect the passage of the rest, and to secure all the further advan tages. 8. Should the enemy, notwithstanding, still at tempt to dispute the passage, our movements must de pend upon circumstances. If we arc too weak to drive him back, we must stop and observe his motions, and make our dispositions accordingly, either to continue the passage, should he neglect the proper opportunity, or to secure a safe retreat for those who have already passed. In the latter case, the enterprise has failed, and we must attempt it in some other manner. But if we are strong enough to bid defiance to the enemy, we must either prepare to receive his attack, if our position be a strong one which covers the passage; or if the passage cannot be completed without timing back the enemy, we must attack him without hesitation, with the troops which have got over, before he is aware.