SIEGE is the process of advancing towards a fortress under the cover of earth thrown up from trenches excavated in the ground ; silencing its fire by a superior fire of artillery and musketry; and finally, by breaching the ramparts, either obliging the defenders to surrender, or forcing an entrance into the place.
A fortress is invested previously to the commencement of the siege by posting troops about it, so as suddenly to occupy all the avenues to the place, and prevent the garrison from receiving succours. The besieging army, on its arrival, establishes itself in the environs of the place at such a distance as not to be annoyed;by the fire of the artillery of the defenders% protecting itself generally by redouts raised at intervals, both on the side nearest to the fortress and on that which is towards the country. [CoussrsaveszeiroN.3 The operations of a regular siege, when conducted against places fortified according to any of the modern systems, arc nearly the same till the approaches (the oblique lines of trenches) arrive at the foot of the glacis; and when, as in the first system of Vauban, the flanked, or most advanced, angles of the bastions and ravelins are nearly at equal distances from the centre of the place those approaches may be directed along the produced capitals (lines imagined to bisect the angles) of a ravelin, and of the nearest bastion on each side of it ; since then, when the glacis before those works is crowned by batteries, the rampart of the enceinte may be breached in two places at once. But systems which, like that of Cormontaingne, have very salient rave ling, the approaches should be directed along the produced capitals of a bastion, and of the nearest ravelin on each side, because the glacis of the bastion cannot be crowned till the two collateral ravelins are taken; and if the lines of approach were directed as in the former case, it would be necessary to take three ravelins before either bastion could be breached. The lines of approach are carried on nearly in the direction of the produced capitals of the bastions and ravelins, because here the ground is less subject to the direct fires from the fortress.
In commencing operations, the engineers, having ascertained on the ground the prolongations of those capitals, trace, by means of pickets driven in the ground and connected by tapes, the direction of the first parallel trench, generally termed the First Parallel, AAA, which is somewhere about 600 yards distant* frousthe advanced parts, o oo, of the covered-way. This parallel usually extends along the fronts
attacked, and occasionally far enough beyond to embrace the prolonga tions of all the ramparts, a fire from which might be directed against the works of the besiegers : it should terminate at each extremity, if possible, in some natural obstacle, as a morass or a river ; and if no such obstacle exists, a redout may be raised there, in order, by its fire, to oppose any attempt of the enemy to turn the parallel. The trench is executed by numerous working-parties of men, who, being provided with spades and pickaxes, are marched up to the ground after eunset, and are disposed along the line at intervals of four or six feet from each other. The earth obtained from the trench is thrown towards the fortress, in order to form a breastwork; and in the morn ing the men are relieved by others, who complete the parallel where it may have been left unfinished, and dig trenches obliquely towards the rear, for the purpose of having secure communications to and from the view. of the besieged. The general breadth is 10 or 12 feet, but greater width is given in places at intervals from each other, where it may be desirable to collect troops and material.
depSta of materials. All the trenches are sunk three feet below the surface of the ground ; and the earth thrown out forming a mares about three feet high, the troops in them are effectually covered from the The first operations of the worldng-parties take place during the night, in order that some progress may be made before they 'are discovered by the defenders ; but should the latter suspect that ground is being broken, they frequently discharge light-balls, by the light of which they may discover the places where the men are at work. These places being ascertained, it may be expected that the ground will be cannonaded, or that troops will make a sortie from the fortress, for the purpose of intemipting or driving off the workmen; and in order that this intention may be frustrated, the parties are accompanied by a guard of infantry, or covering party, which is placed at about 50 yards in front of the tracing-line. These troops obtain cover possible, or lie down on the ground, that they may not be exposed to the defenders' fire; and in the event of a sortie being made, they are ready to repel it : squadrons of cavalry are also, if the ground permits it, stationed near the extremity of the parallel, that by a rapid move ment they may take in flank and cut off the retreat of the sortie.