SIEGE
SIEGE (Pr. a seat, a sitting down) is the sitting of au army before a hostile town or fortress with the intention of capturing it. With certain elements, the success of a siege is beyond doubt; the result being merely a question of time. These elements are : first, the force of the besiegers shall be sufficient to overcome the besieged in actual combat, man to man. If this be not the case, the besieged, by a sortie, might destroy the opposing works, and drive away the besiegers. The second element is, that the place must be thoroughly invested; so that no provisions, reinforcements, or other aliment of war can enter. The third element is, that the besiegers be undisturbed from without. For this it is essential that there shall not be a hostile army in the neighborhood; or, if there be, that the operations of the besiegers be protected by a covering army able to cope with the enemy’s force in the field. The ancients executed gigantic works to produce these effects. To complete the investment, they built a high and strong wall around the whole fortress; and to render themselves secure from without, they built a similar wall facing outwards, beyond their own position. The first was circumvallation, the second contravallation. It was thus that Caesar fortified himself while besieging Alexia, and maintained 60,000 men within his ring. In modern warfare, it is considered preferable to establish strong posts here and there round the place, and merely sentries and vedettes between.
Let us now assume that a fortress of great strength has to be reduced, and that the force of the enemy in the vicinity has been either subdued or held in check by a covering army. By rapid movements, the place is at once invested on all sides, This step constitutes merely a blockade; and if time be of little importance, is a sufficient operation, for hunger must sooner or later cause the fortress to surrender; but if more energetic measures are required, the actual siege must be prosecuted. Advantage is taken of any hidden ground to establish the park of artillery and the engineers’ park; or if there be none, these parks have to be placed out of range. The besieging force is now encamped just beyond the reach of the guns of the fortress; and their object is to get over the intervening ground and into the works without being torn to pieces by the concentrated fire of the numerous pieces which the defenders can bring to bear on every part. With this view, the place is approached by a series of zigzag trenches so pointed that they cannot be enfiladed by any guns in the fortress. In order to accommodate the forces necessary to protect the workers, the trenches at certain intervals are cut laterally for a great length, partly encircling the place, and affording safe room for a large force with ample battering material. These are called parallels, and they are generally three in number. The distance of the first parallel will increase as small-arms become more deadly; but with the old smooth-bore muskets it was usual to break ground at 600 yards from the covered way of the fortress, while at Sebastopol, ground was broken at 2000 yards, and in the siege of Paris by the Germans, the lines were begun at least 4 miles from the city.
The locality of the parallel being decided on, a strong body of men is sent to the spot soon after nightfall. The attention of the garrison is distracted by false alarms in other directions. Half the men are armed cap-a-pie, and lie down before the proposed parallel; while the other half, bearing each pick and shovel, and two empty gabions, prepare for work. Each man deposits the gabions where the parapet of the trench should be. He then digs down behind them, filling the gabions with the earth dugout; and, after they are filled, throwing it over them, to widen and heighten the parapet. Before daylight, the working-party is expected to have formed sufficient cover to conceal themselves and the troops protecting them. During the day, they—being concealed from the garrison—widen and complete their parapet, making it of dimensions sufficient to allow of wagons and bodies of troops with guns passing along. During the same night, other parties will have been at work at zigzags of approach from the depots out of range to the first parallel, which zigzags will be probably not less than 1000 yards in length. The profile of a completed trench is shown in fig. 1, the shaded portion representing a gabion. As a rule, the defenders will not expend ammunition on the first parallel, for its extent (often several miles) will render the probability of doing material damage extremely small. For this reason also, the dimensions of the parapet and its solidity are of far less importance in the first parallel than in the more advanced works of attack.
The first parallel AAA, fig. 2, being completed, the engineers select points near its extremities, at which they erect breast-works, B, B, to cover the bodies of cavalry, who are kept at hand to resist sorties from the garrison. The length of the parallel is usually made sufficient to embrace all the works of two bastions at least. Sites are then chosen for batteries, C, C, which are built up of fascines, gabions, sandbags, and earth. They are placed at points in the parallel formed by the prolongation of the several faces of the bastions, ravelins, and other works of the fortress, which faces the batteries are severally intended to infilade by a ricochet fire. Other batteries will be formed for a vertical fire of mortars and shell-guns. By these means it is hoped that the traverses on the hostile ramparts will be destroyed, the guns dismounted, and the defenders dispersed, before the final approaches bring the assailants to the covered-way. The sappers will now commence their advance towards the points, or salient angles, of the two bastions to be attacked. If, however, the trench were cut straight towards the fortress, its guns could easily destroy the workmen, and enfilade the approach. To prevent this, it is cut in short zigzags—as at D—the direction always being to a point a few yards beyond the outmost flanking works of the garrison. The side of each trench nearest the fortress is protected by gabions and sandbags, as in the case of the parallel.
At intervals, short spurs of trench, incipient parallels, are cut, as at E, to contain small-arms-men, to act as guards to the sappers. The second parallel is about 300 yards from the enemy’s works, and has to be more strongly formed than the first. It often terminates in a redoubt, F, to hold some .light artillery, and a strong force of infantry, who could assail any sortie in flank; or it may run into the first parallel, as G-, giving easier access for troops than through the zigzags. The second parallel is riveted with sandbags, in which loopholes are left for musketry. After passing the second parallel, the angles of the zigzags become more acute, to prevent enfilading. At about 150 yards, certain demi-parallels, H, are cut, and armed with howitzer batteries, to clear the covered-way, while riflemen also act from it. The third parallel is at the foot of the glacis. Thence the place, after being sufficiently battered, is taken by a storming-party, who make their way over the glacis, or the covered-way is topped by the double sap, as in fig. 3; which is a safer plan for the army general, though much more deadly to the sappers. When the crest of the fig 3—Double Sap. covered-way has thus been reached, batteries of heavy artillery will be there established, for the purpose of breaching the walls of the ravelin and bastion; while at the same time miners will first seek to destroy the defenders’ counter-mines (which would otherwise be likely to send these batteries into the air), and then will excavate a tunnel to the ditch, at the foot of the counterscarp.
If the breach becomes practicable, a storming-party will emerge from this tunnel or gallery, and seek to carry the opposite work by hard fighting. If inner works still subsist, which would tear assailants to pieces, the double sap may be continued across the ditch, if a dry ditch, right up the breach, that counter-batteries may be formed. If the ditch be wet, means must be adopted for a causeway or a bridge. By these means, however obstinate may be the defence, if the besieging force be sufficiently strong, and aid do not arrive from without, the ultimate success of the attack becomes certain. Vauban raised attack to a superiority above defence, first, by the introduction of ricochet fire, which sweeps a whole line; and secondly, by originating parallels. Before his time, the whole attack was conducted by zigzag approaches; in which the troops actually in front could be but few, and were therefore unable to withstand strong sorties of the garrison, who, in consequence, frequently broke out and destroyed the works of the besiegers, rendering a siege an operation of a most uncertain character.
