Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/444

430 FORTIFICATION construction would be greatly increased by having no inter mediate stage between the bottom of the ditch and the top of the parapet. The " berm," or step between the top of the escarp and the bottom of the parapet, is made from 1 foot 6 inches to 4 feet wide, according to the nature of the soil, and it then becomes possible in some cases to increase the slope of the escarp to a base of one-half or two-thirds, or at least to such a slope as shall place the foot of the escarp in the prolongation of the exterior slope of the parapet. The berm is encumbered with obstacles to prevent an enemy from making use of it as a halting place (see fig. 14). The slope of the counterscarp is usually one-third, one-half, or two-thirds, when that of the escarp is one-half, two- thirds, or 1 ; the bottom of the ditch should slope from the sides to the centre, to carry off the water, and obstacles should be provided there to prevent the enemy from col lecting and reforming his men in the ditch, which, in all cases of simple lines, without flanking defences, he would do were it left free from obstructions. FIELD FOETIFICATION. The parapet has been hitherto considered principally in its character as the simplest element of defence, affording at once protection to the soldiers behind it and obstruct ing the advance of their enemies ; but it is now time to consider the manner in which this parapet may be so arranged as to constitute a series of defensive and mutually defending works. If the antiquity of an invention be estimated by its position in the social history of the races of mankind, there can be no doubt that earthworks claim the priority over other forms of defence. In North America vestiges of circular earthen intrenchments, as well as of works of other forms, have been discovered, the antiquity of which is unknown ; and in more recent times small parties of the aboriginal inhabitants encountering greater numbers of a hostile tribe have been known to exca vate hollow spaces in the ground, and, throwing out the earth, to form around them circular intrenchments in which they have defended themselves to the last. In Ireland the ancient inhabitants have left similar relics of their earthen defences ; in Great Britain there are numerous similar remains, the works of the Romans and of people long antecedent to the Romans ; but the consideration of earthen works for the defence of extensive positions will be resumed further on, and such works will be considered here only in connexion with the arrangements adopted by an army in the field for its own immediate security. The art of constructing temporary works in the field for this purpose is called Field Fortification. This art is of very high antiquity ; the Roman soldiers relied much upon such works, and executed them with wonderful rapidity, even in the presence of an enemy. Shelter Trenches. Of this art the simplest form is that in which troops are preserved intact until the moment of attack arrives. At first sight it would seem that this can best be effected by keeping them out of fire. The increase in the range of arms of all kinds has, however, become so great that it is no longer possible to keep troops out of fire and yet in a sufficiently advanced position from which they shall be able to attack promptly ; hence it has become an absolute necessity to provide shelter for them. A very shallow trench with the earth thrown to the front will afford, to men lying in it, cover against artillery fire, and a good rest for their arms when they have occasion to deli/er their own fire. Moreover, it presents no obstacle to the advance of supporting troops, and offers but little mark to the enemy. Such trenches (figs. 27, 28, 29, 30) are called shelter trenches, and may be made of any depth or form according to the time and means avail able. They are very difficult of capture by the front attack, when defended by trained troops with breech-loading rifled . ,. 5.0 - FIG. 27. Shelter Trench, constructed in 25 min. to J-hour. arms, and can be quickly developed into regular intrench ments. The ordinary forms of shelter trench in use in the British army are shown in figs. 28, 29, and 30. The Russians made use of shelter trenches with FIG. 28. Shelter Trench,! hour. effect in the defence of Sebastopol, and since that siege their employment has steadily developed. In more recent times the greatest use of hasty intrench ments, though perhaps in the form rather of a line of FIG. 29. Shelter Trench,! hour. intrenchments than of shelter trenches, was made by the Americans in the war of secession. Wherever they halted, no matter how short the time at their disposal, they threw up shelter. Each man worked for himself, and as if FIG. 30. Shelter Trench, 3i hours. by instinct, and before fires were lit or provisions cooked, an intrenchment of some kind was formed. Probably the Americans had acquired this habit in their campaigns against the neighbouring Indians; and no doubt tlir superiority of rifled small arms, then for the first time freely used, thoroughly imbued them with a sense of the value of the slightest protection. General Sherman s campaign in Atalanta, and the actions in the neighbourhood of Rich mond and Petersburg, furnish numerous instances. With reference to them General Barnard reports that a simple trench defended by two ranks of foot soldiers is an obstacle unassailable by direct attack. General Wright relates that, attacking a handful of infantry, in single rank, behind a parapet and trench, with two divisions in line, the num ber of his casualties exceeded the number of the enemy, and that if the intrenchment had been defended by two ranks of good troops, a whole army corps would not have taken it ; and in summing up his relation, he says that a simple trench, defended by two ranks of foot soldiers, covered by abattis and other obstacles, placed so that the new rifled arms have full scope, is absolutely impregnable except by surprise. After the fall of Nicopolis in August 1877, 28 battalions