The defence of all other defiles may also be conduct ed according to all the three methods above described : and the two first always depend upon preventing the debouche. But in the vase of these other defiles, another method still remains ; which is, to 'establish ourselves within them, by means of fortresses or redoubts. If such posts cannot be turned, or when placed on hills, if they arc not commanded by higher eminences, they render the passage of the defile impossible. In establish ing such posts, therefore, we must have these circum particularly in view, and also to keep the road itself completely under their fire.
elf passage of a river or other defile, with the view of placing it between us and the enemy, is, on this ac count, a matter of difficulty, because there is a period at which the army is divided, and the enemy can at tack it at the greatest possible advantage. In such a case, we may either conceal our intention, or we must effect it in the face of the enemy. The following are the general roles applicable to both cases. 1. All the baggage, heavy artillery, and all the carriages that can be dispensed with, should be sent far before us, to some secure place. 2. A strong position should be taken close to the river ; and the more close, if we can conceal the time only, and not the place where the passage is to be effected; but, at all events, in such a manner that we may be able to march upon several points of it. 3. Behind this position, bridges should be thrown, shortly before the march, and secretly, if we wish to conceal the place ; but otherwise, at the most convenient points, and without any attempt to conceal our intentions. 4. If there be positions on the opposite bank of the river which can cover the passage, they should be occupied with troops and artillery, and strengthened, if necessary, by redoubts. 5. The pas sage should be made in a continued and orderly man ner, but without hurry, until all have passed, except the detachment which is destined to break down the bridges, and which must afterwards pass over in boats. 6. In case of being attacked by the enemy, we must make a proper use of all the means of defence which we have prepared, without engaging with him farther than is necessary to secure the passage. Besides, we must endeavour, in the first case, to seize the first fa vourable moment to effect the passage, and, if possible, to deceive the enemy by fallacious movements, with respect to the real point. When this cannot be done,
we should endeavour to conceal the time, by breaking up during the night, or in the midst of a thick fog, a storm, &c. and employing all kinds of warlike strata gems. Notwithstanding all these precautions, we must not neglect to take every measure for securing the pas sage against accidents. The rear guard must occupy all the posts that can cover and protect it, and all must be prepared to assist it, in case of necessity.
When it is not possible to conceal from the enemy either the place or the time of the passage, and he has it in his power to attack us at any time, it w ill be ne ceesary to adopt the additional precaution of entrench ing ourselves in several lines, so that when the army has beeen weakened by the passage of a part, the rest may not have too extensive a line of defence. No thing should be neglected that can tend to conceal the retreat. In the case of other defiles besides rivers, there is little difference in the dispositions, except that the precautions employed to cover the passage at the opposite side are unnecessary, and all our attention, therefore, must be turned to the rear guard, which can only be slowly succoured.
It is unnecessary for us to say any thing of the means of passing a defile, when the enemy is master of both sides, and the army, in attempting thepassage, must cut its way through ; because this is quite a des perate situation, out of which it is almost impossible to extricate ourselves, and into which no general can fall, without gross errors and incapacity. In such a case, we should have to contend with the twofold difficulties of a retreat, and the forcible passage of a defile. Sue cess in such a case must be ascribed to good fortune, and not to good conduct.
In order to prevent the retreat through a defile, it is necessary, I. That we should be vigilant, to prevent the enemy from effecting the passage secretly. 2. That we have an accurate knowledge of the enemy's situa tion, that we may regulate our project of attack ae cotdingly, and carry it into execution before he has time to effect his 'object; for which purpose we must drive him as close to the river as possible, in order that he may not be able to conceal from us the point where he means to pass. 3. That we should make such dis positions as will enable us to make an attack every moment, especially during the night, by keeping the troops, cavalry, infantry, and artillery, constantly in readi ness.