If the interior arrangement of the work is known by the besieger the assault maybe made by night; but if it is unknown, the confusion resulting from a night attack will be so great as to render its success almost hopeless, and the assault will have to be delivered by day.
The assaulting columns will be made up of an advanced line of skirmishers (selected men, good shots, and generally volunteers), followed by a working party of sappers to clear away obstacles, these closely followed by the columns of assault; while the supports and reserves move forward in the trenches to join in the assault as circumstances require. The troops who first gain the crest establish themselves there and hold the breach until those coming after them pass and engage the garrison, while some detachments strive to capture and open one gate or more to admit the reserves. The assaulting force should be equal at least to once and a half or twice the garrison, and simultaneous attacks should be made upon other breaches or accessible parts of the work to divide the attention of the defence.
These false attacks are sometimes successful, and preparations for taking advantage of this contingency should not be omitted. The subdivisions of the assaulting force should each receive explicit instructions as to its special object, and under no circumstances should their lines of march intersect. Unmistakable signals of recognition should be prescribed to prevent conflicts arising between the different parties meeting within the work. The bombardment preceding the attack should not cease, and thus notify the defence when the assault is to be made; but the guns should be directed upon adjacent parts of the work until the assault penetrates the work or is repulsed.
94. In the attack by the sap the method of crossing the ditch adapted to the circumstances is used (pars. 39-41, [Pl. IV], Figs. 37-41) and the sap is started at the foot of the breach, driven up it, and the breach is crowned according to the methods previously described (par. 36).
The sappers are protected from small sorties by the fire from the crowning of the covered way and any other points bearing on the head of the sap. Fireballs, electric lights and other means will be used during the night to light up the parapets of the work and expose the defenders, in this as in the previous operations of the siege. The crowning of the breach will be extended and converted into a place of arms, from which further sapping can be carried on in a similar manner, until the breach in the last retrenchment is crowned and the preparations for the final attack upon the garrison are made, or the place surrenders. If the garrison takes refuge in an interior keep and continues the defence the keep must be reduced by similar methods.
95. Additional Operations in the Attack of an Intrenched Camp.—The operations above described are those necessary to reduce a fortified place of the older type, or a detached work of an intrenched camp. The latter, though of less extent and with a smaller garrison, offers as a rule greater resisting power, since it is usually subject to front fire only, has more complete bomb-proof cover, and is free from the presence of non-combatants.
While a great advantage is gained by the capture of two or more of the advanced forts, the resisting power of the intrenched camp is by no means destroyed. These forts are subject to the fire of the collateral works, of which frequently two or more must be silenced before a further advance can be made. The beleaguered army may still be in condition to recapture the forts by vigorous assaults; and in almost every case, before the fall of the works of the outer line, a line of provisional fortifications of high resisting power, connected by trenches, will have been constructed by the defence in rear of the captured works, with its flanks secured by the collateral works of the outer line. An assault against works of this class offers no prospect of success. The besieger is therefore obliged, as soon as he captures a detached fort, to put it in condition to withstand the assaults of the besieged army and to afford protection from the artillery fire of the collateral works, and then to push forward his approaches against the successive positions prepared by the defence, which will as a rule present a front equal to or greater than that which can be occupied by the attack. The gorges of the captured works are repaired and strengthened, covered communications are made through the faces, either through the breaches or in more convenient points, traverses are repaired or built to protect against the fire of the collateral works, and the captured works are connected by trenches which afford emplacements for batteries and form a new parallel from which the saps can be driven in attacking the intermediate works. Simultaneously with this attack, it is usually advisable to advance from the flanks of the first or second parallel upon the forts of the outer line which form the flanks of the intermediate line. The approaches can generally be driven with comparative ease owing to these works having already been partly disabled and now being subject to a flank and reverse fire from the newly-established batteries.
The flanks of the intermediate line being turned by the capture of these works, a portion or the whole of it will of necessity be abandoned. The subsequent operations up to the capture of the enceinte will be of the same nature as those already described.
96. Occupation of a Conquered Place.—Immediately upon the fall of the place it must be occupied by a force (chosen when possible from the reserve which has not participated in the final assault) sufficient to control not only the inhabitants, but also the disorderly soldiers of the attacking force. All pillaging, wanton destruction, and abuse of the conquered must be restrained with a strong hand, immediate and exemplary punishment being inflicted upon offenders. The orderly portion of the defenders must be protected, and such steps taken for supplying their needs as humanity requires; while the disorderly ones must be repressed with such severity as may be necessary. So soon as order is established a careful inventory of captured property is made, and it is stored subject to the orders of the government. When the possibility exists of the place being attacked or besieged by the enemy, all its resources which are available for defence are collected, repaired, and stored for use.