Page:The American Cyclopædia (1879) Volume XV.djvu/37

 SIEGE 29 advanced point of the fortification, from 3 to 4 ft. deep and 10 to 12 yards wide, and throw- ing 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 thosl 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 trouble- some ; but the distance will be materially af- fected by irregularity of site and the size and kind of cannon used. At Sebastopol in 1854 the French established their first paral- lels, 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 Wag- ner, 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 siegers 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 par- allel. 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 wri- ters 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 nar- rowed 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 re- quire them. When advanced not quite half way between the first parallel and the fortifi- cation, they are connected by a second parallel, which in all essential particulars except in ex- tent 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 forti- fication,^ 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 par- allels. They serve as places of arms in which troops are stationed to protect the workmen and to resist sorties, as communications be- tween the approaches, and to keep these free for the workmen and clear of troops. Only th'ree, and the demi-parallels K, K, are shown in the plan, but there are often many more. At Sebastopol the French constructed sev- en, 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, dis- mount 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 en- closed 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 ap- proach is exposed, and are constructed by en- gineer soldiers called sappers. When the foot of the glacis is reached, from 60 to 30 yards from the salient, the third parallel is con- structed, 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 th'e 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 be- sieged, accompanied by many difficulties in the construction of the necessary works for pro- tection. 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 im- proved 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