97. Marshal Vauban, the great French military engineer (born 1633, died 1707), whose experience and success in sieges made him the great authority on the subject, formulated certain maxims for governing the conduct of a siege, the observance of which led to almost certain success, and the departure from them almost invariably resulted disastrously. The most of these are as applicable to sieges of to-day as they were to those of his own time. The following[6] bear upon the second and third periods of the attack:
1st. To delay the opening of the trenches until the besieging forces are all well posted and made secure by fortifications from an attack either from the garrison or from a succoring force; and until everything requisite for carrying on the work vigorously has been collected and is ready at hand when wanted.
2d. To make a single attack rather than a double one, unless the two attacks can be well connected and the besieging force exceeds considerably in strength the garrison. This, as a matter of course, excludes false attacks, and double separate attacks, unless the superiority of the besieging force is very great. By a single attack is understood one by which it is proposed to gain possession of the main work by a single breach at some point; by a double attack it is proposed to effect two breaches of the main work. The advantage of the latter lies in forcing the garrison to divide their strength for the defence of the two breaches, whilst the assailing forces, being under one leadership, can at any moment concentrate if necessary upon the point most favorable to their assault.
3d. To embrace within the parallels and approaches all the defences which bear upon the site to be occupied by the besieger’s works, in order to have secure positions for establishing the batteries that may be required to silence the fire of these defences.
4th. To multiply the approaches, with the view of giving mutual support, less encumbered communications, and dividing the fire of the defences, which, if concentrated upon a single one, might soon destroy it.
5th. To throw up at least three main lines of parallels, placing them in the best positions for mutual support and for guarding the approaches and batteries from sorties of the besieged.
6th. To avoid attacking a point upon which the approaches can be run only on a narrow front, or one which can only be approached over marshy ground, or on causeways.
7th. To be careful not to push forward any portion of the trenches until they are well flanked and protected by trenches in their rear, which are completed and occupied by troops.
8th. To avoid encumbering the approaches with trench materials, tools, workmen, or troops; placing all of these in the parallels, on the right and left of the approaches, so as to be ready at hand when wanted, and to be rapidly sent forward through the trenches of the approaches, which should be kept free for this purpose.
9th. To place the ricochet (enfilading) batteries in such positions that they can have an enfilading and slant reverse fire upon the guns of the defences to be attained by them.