Siege (Fr. Siege Seat), a protracted military attack upon a fortified place. Such a place may sometimes be taken by throwing in heavy projectiles, explosive shells, incendiary balls, etc.; or by completely surrounding it, preventing reception of supplies, the defenders may be compelled to surrender; or, advancing by regular approaches, the besiegers may breach the walls, and carry the place by assault. The first is called a bombardment, the second a blockade, and the third a siege, which term is often also applied to the other two. In a strict sense, the term siege signifies the process of advancing toward a fortified place under cover of earth thrown up from trenches, silencing the fire from the work by a superior one, and breaching the ramparts, compelling a surrender or carrying the place by assault. Sieges are divided into ancient and modern, or those carried on before and after the application of gunpowder to military purposes. - Ancient Sieges. The ancients fortified a place by surrounding it with a wall of brick or stone, forming a continuous line around the city or town, high enough to render escalade difficult, and thick enough to offer considerable resistance to the battering ram. Sometimes there were two and even three of these walls, often connected by others to give them greater solidity.

Outside of the wall was a ditch, always filled with water if circumstances permitted. The inhabitants were the defenders; and as their lives, liberty, and property were involved, the resistance in ancient sieges was more obstinate and persevering than that usually made in modern times. The modes of attack were by surprise, aided by treason or particular knowledge of unguarded points; by escalade, having surprised the place; by escalade in an assault, having outnumbered and overpowered the defenders; by blockade, having deprived them of supplies; and by regular siege operations. When the siege seemed likely to last some time, the ancients were in the habit, if they expected sorties from the place or an attempt to relieve it from without, of securing their position by a double line of works, of circumvallation and countervallation. These were generally continuous lines constructed of earth, wood, and sometimes of masonry, flanked by towers. Annoying the besieged with missiles thrown from all the artillery known in that day, they pushed forward covered approaches on the points of attack. These were wooden frames, 7 ft. high, 8 ft. wide, and 16 ft. long, mounted on wheels, with a roof strong enough to resist the projectiles thrown by the besieged.

They were covered with raw hides or turf, or protected by other expedients from being set on tire. The ditch when reached was filled with earth, logs, and stones, upon which the battering ram could be placed in position to breach the wall; or a descent was made into it for the purpose of undermining the wall. The battering ram was ordinarily placed in the lower story of a tower and suspended by chains or other mechanism. The tower was high enough to command those of the place, and was filled with armed men, who drove the defenders away from that part of the wall in its front. They were frequently aided by other towers pushed along on the ground or on inclined planes. The besieged, besides shooting lighted arrows and throwing incendiary compositions against the approaches, made sorties, which were usually bloody in their results, for want of covered ways or other exterior works beyond the ditch. The battering ram being in position, the besieged suspended beams of wood, stuffed contrivances like huge mattresses, and other devices, between the head of the ram and the wall, to deaden its blows. They sometimes used machines on the principle of the crane, by means of which they caught the head of the ram, or even the whole engine, and lifted it from the ground or overturned it.

Archimedes devised such machines for the defence of Syracuse when it was besieged by the Romans, in 214-212 B. C. The wall being breached by the ram, or thrown down by undermining, preparations were made to assault the place through the opening. Often, while the besiegers were engaged in removing the ruins from the breaches, so that an assault could be made, the besieged were building a new wall in rear of the breach enclosing the part attacked, and the whole operation of moving forward the battering rams and breaching the wall had to be renewed. The surrender or capture was generally due to the exhausted condition of the besieged, rather than to the assaults. It was the custom for the besieging army to demand a surrender before they began the siege; and usually the besieged offered to capitulate before the final assault was made, as a hopeless resistance entailed death or slavery on all the defenders. Even in modern times the lives of the garrison are jeoparded if the besieged delay making terms until the final assault is successful. - Transition Period. The introduction of gunpowder in military operations led to the substitution of earthen trenches for the wooden covers and other ancient expedients, and also replaced the battering ram by heavy cannon.

In this period, owing to the imperfection of the artillery, the want of connection between the approaches, and other deficiencies in the measures of attack, the besieged were often able to make a vigorous and prolonged defence, and sieges became the most important military operations of the time. Before 1741 there were more sieges than battles; from 1741 to 1783 the proportion was 67 sieges to 100 battles; during the French revolution the proportion was about 25 to 100; and during the first empire there were only 16 sieges to 100 battles. In recent wars these proportions have still further diminished. But the necessity for sieges still exists, and the rules and practice of taking a fortified place still hold a prominent position in the military art. The present method of attacking a fortified place by regular approaches is practically that organized by Vauban. Previous to his time, the middle of the 17th century, although many sieges had terminated successfully, there was no uniform system in the modes of attack.

Vauban is especially credited with the invention of ricochet firing, the concentration of enfilading batteries, and the systematic arrangement of the parallels. - Modern Sieges. Let it be supposed that siege operations are to be conducted against a fortified place immediately upon the theatre of war. As the operations against a place fortified by any of the modern systems are governed by the same general conditions, and are practically the same until the besiegers reach the counterscarp of the ditch, the methods used will be fully explained by considering the mode of conducting an attack on a place fortified by the bastioned system. (See Fortification.) To simplify the explanation, it is supposed that the front to be attacked has the usual outworks and occupies a horizontal site, and that the cannon used by both the besiegers and besieged are the ordinary smooth-bore siege artillery. Irregularity of site and the use of heavier calibre or rifled cannon will only have the effect of increasing certain distances and adding to the difficulties of the siege, without affecting the principles common to them all.

As the scarp walls are hidden from the besiegers' view by masks of earth, the object of the siege works is to reach, under cover, positions where openings in the walls can be made either by breaching batteries or mines; and under the shelter of these approaches troops can be brought up to make assaults through the openings. In this front, in order to make a breach in the scarp by artillery fire that will be practicable for the assaulting column, the cannon must be x>laced on the crest of the covered way, and to make it accessible a descent into and passage of the ditch are necessary. If it is proposed to make an opening by mining, all the preliminary operations as far as the glacis of the work are identical. If the main work has outworks from which a reverse fire can be had on that part of the covered way where the breaching batteries are to be placed, they must first be taken. The accompanying plan will aid in explaining practical siege operations. The attack is made on bastion A, and as the adjacent demilunes D, D, those on the right and left of A, place the covered way of this point in a reentrant angle, these demilunes must be taken before the bastion can be breached.

This bastion and the adjacent demilunes with their outworks must be taken by breach or assault, and the fire from the collateral demilune 0 and bastion B shown in the plan, and the corresponding ones on the left not shown, must be kept under by opposing batteries during these operations, to enable the besiegers to carry on their work successfully. Approaches are made on the three salients, A, I), D, and these connected by parallels to hold large bodies of troops to protect the workmen and repel sorties. The siege operations may be divided into two general parts, one including all the measures taken to prevent ingress and egress, the other those required to gain possession of the place; but for convenience they are ordinarily classed into three parts, called the first, second, and third periods. The first period comprises the investment and the encampment of the besieging army around the place; the second, all the works from the opening of the trenches until the completion of the third parallel; and the third, all subsequent measures until the place is taken.

The investment is performed by detaching a strong corps, who, moving quickly and secretly, suddenly surround the place, seize all avenues of approach, cut off all communications, and secure everything that may be of service to the defence. The main army follows and intrenches in positions around the place outside of cannon range. The intrenchments ordinarily form two lines, between which the besieging army places its camps, and are called lines of circumvallation and countervalla-tion. They may be continuous or with intervals, the outer line being used to prevent succors, and the inner to resist the attacks of the garrison. This method of constructing lines and enclosing the army between them was used by the ancients, and fell into disuse during the middle ages. It was revived in the 16th century by the princes of Nassau, and has been practised more or less ever since. These lines not only enable the besieging army to repulse detachments that try to reenforce the place, but are also useful where the besieging army is forced to take up weak positions to complete the investment. The strength of the besieged work, the nature of the ground, and the facilities for transporting troops and supplies from the depots are governing considerations in selecting the front of attack.

Salients are usually the weakest points of a fortification; low, marshy soil and rocky ground present the greatest difficulties in constructing siege works. - The second period begins with the opening of the trenches, which is done by digging a ditch or trench, between GOO and 700 yards from the most advanced point of the fortification, from 3 to 4 ft. deep and 10 to 12 yards wide, and throwing up the earth in the form of a parapet on the side toward the work. This trench and all similar ones are constructed according to the general rules for throwing up field works; that is, they must afford a shelter from the enemy's fire, and permit those occupying them to use their arms with effect. The trench is extended far enough on each side of the point of attack to embrace all the positions required for batteries to keep down the fire of the collateral works. From its being parallel to or concentric with a line connecting the most salient points of the work, it is called the first parallel. At this distance, the fire of the besieged upon the workmen in the obscurity of twilight and darkness will not be troublesome; but the distance will be materially affected by irregularity of site and the size and kind of cannon used.

At Sebastopol in 1854 the French established their first parallels, one at nearly 1,000 and the other at 1,800 yards, and the English at 1,800 yards, from the defences in their front. At Fort Wagner, Charleston harbor, in 1863, Gen. Gill-more opened his first parallel at 1,360 yards from the works. Accidents of the ground may enable the besieger to place it much closer. Communications are opened from the parallel to the depots in the rear, by trenches of the same general form, so arranged as to avoid an enfilading fire from the fortifications. As the besiegers desire to get as near as they can to the point of attack with as little sacrifice of life as possible, they make their advances by means of trenches similar in form to the parallel. These are pushed forward toward the point of attack, running in zigzag directions, crossing and recrossing the lines of the capitals of the salients, and avoiding enfilading fires from any point of the defences within cannon range. The approaches, called by many writers boyaux or branches, are as a general rule not longer than 100 yards, and, starting at the first parallel with a front of 60 yards, are narrowed to 30 yards at the third parallel. In this position along the capitals of the salients, they are less in the way and less exposed.

These are shown in the plan, one to each salient, or three in this particular case, but there should be more if 'the circumstances require them. When advanced not quite half way between the first parallel and the fortification, they are connected by a second parallel, which in all essential particulars except in extent is like the first. Being constructed within destructive range of case shot, the flying sap is used instead of the simple trench, as more speedy cover for the workmen is obtained by it, and differs from it only in having the interior slope revetted with gabions. Being nearer to the first parallel than to the fortification, it is protected from sorties made against it in its unfinished condition, and its object is to protect the approaches as they are pushed forward from it. Vauban prescribes that there shall be at least three of these parallels. They serve as places of arms in which troops are stationed to protect the workmen and to resist sorties, as communications between the approaches, and to keep these free for the workmen and clear of troops. Only three, and the demi-parallels K, K, are shown in the plan, but there are often many more. At Sebastopol the French constructed seven, and at Fort Wagner Gen. Gillmore used five.

Whatever the number, they should be placed in good tactical relations with each other, not so far in advance that the troops occupying the one in the rear cannot come to their support before they are reached by a sortie from the fortification. The besiegers place in front of the second parallel mortar, ricochet, and counter batteries, which, firing upon the work, break down the palisades, dismount the guns, and drive away the defenders. The use of rifled guns will cause these batteries to be placed further away from the work than is here represented, probably from 2,000 to 3,000 yards, in which case they should be enclosed in small works with a sufficient number of men in each to defend them. From the nearness to the work, the advance from the second parallel can only be made by means of saps. These are the flying, single or full, the double and half double saps, according to the direction and amount of fire to which the approach is exposed, and are constructed by engineer soldiers called sappers.

When the foot of the glacis is reached, from 60 to 30 yards from the salient, the third parallel is constructed, demi-parallels which are long enough to contain troops to protect the workmen, and short enough not to hinder the fire from the batteries, having been made between it and the second parallel. The second period ends with the construction of the third parallel. - Thus far the advance and progress of the siege have been made without any great degree of difficulty or danger. This is now changed, and if the defence is vigorous future progress must be made under a murderous fire from the besieged, accompanied by many difficulties in the construction of the necessary works for protection. The advance on the nearest point of the covered way from the third parallel is by assault or by regular approach. The former is more rapid and more brilliant, but is seldom successful, and ought never to succeed if the besieged are not entirely exhausted and make even an ordinary resistance. It has been shown in recent wars that a single trench, defended by two ranks of infantry armed with the improved weapons of the present day, is almost unassailable by main force.

In an attack by two divisions of infantry on a continuous trench before Petersburg, Va., defended by a single line of infantry, the number of the at-tacking force killed exceeded the total effective strength of the defenders. If it be decided to make the assault, the third parallel is arranged with steps on the inner side to allow a detachment of picked men to sally out at a given signal with a front equal to that of the assaulting column. They are preceded by engineer officers, who mark out the lines for a trench four or five yards from the crest of the glacis, and extending around the salient place of arms, and are followed by a detachment of engineer troops to construct it. When everything is in readiness, all the batteries open fire on the place. At a given signal they cease, and the column of assault rushes forward and takes possession of the covered way. The engineers immediately make the sap, into which the troops retire if successful, and afterward connect it by suitable communications with the third parallel. The execution of this trench around the salient place of arms is called crowning the covered way. In 1708, at the siege of Lille, the covered ways of two of the salients of the front of attack were crowned by assault.

The attack was made at nightfall by 10,450 men, not counting the troops in the trenches; they lost 2,000 killed and 4,000 wounded. The best engineering authorities are opposed to an assault except in case of urgent necessity, when a day gained may decide the fate of the besiegers themselves, or the time saved by it compensates for the immense loss of life that must accompany it. If the advance is to be made by regular approaches, they are started from the third parallel by saps, which when within 30 yards of the salient are spread out in a circular form to enclose it, and high mounds of earth, called trench cavaliers, are thrown up, by which a command over the covered way is obtained. Protected by them, the engineers advance their saps to the salients and extend them to the right and left along the faces, at least as far as the traverses, as in the case when the assault was. made. As soon as this is done, they proceed to establish counter and breaching batteries to fire against the demilune and bastion. The former are placed around the salients so as to fire in the direction of the ditches against the portion of the work by which they are swept, while the latter are placed near the counter batteries and nearly opposite to the points where the breaches are to be made.

Underground galleries are also constructed, by means of which a descent into the ditch can be effected. A breach is considered practicable for assault when the interior of the work is exposed for a width equal to the front of the column of attack and the debris forms a slope of easy ascent. If breaches are to be made at several points, the operations should be carried on and the assaults made simultaneously. The breach in the demilune will be carried by assault or by regular approach, and in all essential things there will be no difference in the mode of taking it from that described for the covered way. As soon as the breach is gained, it is crowned, or a lodgment made by encircling it with a trench in which troops are placed to prevent the besieged from regaining possession of the work. The demilune being taken, advances are made against the reentrant places of arms and salient of the covered way of the bastion, if they have not already been crowned. Other batteries are established against the faces and flanks of the bastion, and operations similar to those already described are carried on against the main work.

A capitulation will ordinarily follow the crowning of the breach in the bastion, unless there are interior retrenchments, in which case the same method of attack will be followed until there is no longer any defence between the besieger and besieged. The breaches are supposed to have been made by battering the ramparts with artillery fire. The other method is by means of mines, which are rarely used because of the slowness of the operation and the uncertainty of the result. The explosion of the mine gives no practicable slope for the use of the assaulting column, and this must be made by workmen before it can be used, which is very difficult and dangerous. To resist the approach of the besiegers, the defence make use of mines; to destroy these, and to advance their works, the besiegers also employ them. They will be most largely used between the third parallel and the main work. The passage of the ditch is a difficult and dangerous operation, rendered doubly so when the besieged have a wet ditch, or can make use of water in their defence. In an actual siege, a daily record is made by the engineers of the amount of work done and the time required, which is transmitted to headquarters and preserved.

By comparisons of these records and the results obtained in engineering schools, the time necessary to complete all these works has been calculated. This time has been used in comparing the relative value of different systems or methods of fortification, by submitting them to a fictitious siege. It is of no value in practice, for the duration of sieges depends on laws which no method of calculation can determine. In order that the besiegers should be successful, their numbers and their armament should be in excess of those brought to resist them, and no fixed rules can be stated for this excess. As a general rule, supposing the investment to be complete, the besiegers should be about six times as numerous as the besieged, and should be kept so by sending the wounded and sick to the rear and replacing them by fresh troops. As the defence have not this resource, their numbers constantly dwindle until they are exhausted or overpowered. - Among the most celebrated sieges in history are those of Babylon, Tyre, Syracuse, Carthage, Numantia, and Jerusalem in ancient times, and of Constantinople, Antwerp, Ber-gen-op-Zoom, Stralsund, Candia, Lille, Buda, Schweidnitz, Saragossa, Sebastopol, Vicksburg, Strasburg, Metz, and Paris since the introduction of gunpowder.

1. Half of Plan of regular Approaches against a Front of Attack. A. Point of attack. B. Adjacent bastion. D. Demilune of front of attack. C. Collateral demilune. E. V. Trench connecting first and second parallels. K. K. Demi-parallels. M, M, M. Enfilading, counter, and mortar batteries. T, T. Troops, called guards of the trenches, protecting the workmen on opening the first parallel.

2. Section showing Slopes and Dimensions of Profile of Approach by simple Trench.

A bastion corresponding to B, demilunes to C and D, and approaches on the left of A, are supposed to be indicated and to form the whole front of attack.