Early Walls and Fortifications
The records of history and the vestiges of remote civilization show that the art of fortification, in some guise or another, has been in practice throughout all nations, even in the lowest stages of social progress; and that, wherever it has been cultivated, its character has been more or less influenced, not only by the natural features of the country, but by the political and social conditions of its inhabitants. In its earliest applications, men resorted to one or more simple enclosures of earthen walls; or of these surmounted by stakes placed in juxtaposition; or of stakes alone firmly planted in the ground, with a strong wattling between them; or of timber in its natural state, having its branches and the undergrowth strongly interlaced to form an impervious obstruction, with tortuous paths through it only known to the defenders.
The wall built by the Komans, between Carlisle and Newcastle, to restrain the incursions of the Picts into the southern portions of the island, was sixteen miles in extent, about twelve feet in height, and nine feet in thickness. The extent and dimensions of this work sink almost into insignificance when compared with those of the celebrated wall of China, built to restrain the incursions of the Tartars. This structure is about 1500 English miles in length; has a height of 27 feet; its thickness at top is 14 feet. The lower portion of it is built of dressed stone, the upper of wellburned brick. It is flanked at distances of about 80 yards apart by towers in which iron cannon are found.
The walls of fortified places in the Middle Ages consisted of curtains and towers; the curtains high enough to make fortification, escalade difficult, and with a width of 2 or 3 yards only at the top, made up of the battlemented parapet wall with a narrow path behind it; the towers higher and more massive, projecting in front of the curtain and flanking both the face and the top of it.
"The Ancients," says Vegetius, "did not think it well that Flank the wall enclosing a place should be carried straight, and so lend defence, itself to the blows of the battering rams, but preferred to make it alternately salient and re-entering, and built numerous towers at the angles. Hence, if any one attempts to bring up ladders or engines against a wall so constructed, he is hemmed in, and assailed not only in front, but also on the flanks, and almost in rear."
Consequently, besiegers preferred to attack acute salients, which, owing to the short range of the engines for hurling projectiles, were necessarily ill flanked. While, therefore, such salient angles were avoided as much as possible in fortifying a Elace, where they were unavoidable the corner tower was made irger and higher than others; its front was made to jut outwards so as to form a horn or beak, offering greater resistance to the ram or sap, and admitting of better defence from the curtains; obstacles were multiplied in front of it, and arrangements made for retrenching in rear of it in case of its capture.
It was the feudal castles, rather than the cities, that most often defied capture. Cities were more amenable to blockade, and, besides, their sites had not usually been chosen with a single eye to defence. The castles were placed on commanding bluffs, or spurs, with steep slopes, altogether inaccessible by the engines of the besieger, and were usually approachable only on one side, perhaps by a narrow ridge.
The improvements in the construction of guns and of their carriages, and the substitution of cast-iron for stone shot, in the latter part of the fifteenth century, made artillery much more formidable. The bold heights whose steep slopes gave security against the cat, the beffroi, and the trebuchet, could give no such security against the cannon shot; and the new dangers of the mine made it necessary to come down from the hills, and to seek safety, not by rising above the ground, but by sinking into it.
"If the walls be made high," says Machiavelli, "they be too much subject to the blows of the artillery; if they be made low they be most easy to scale." How to escape this dilemma was the problem to be solved. For the wall itself various methods of construction were adopted in new works. Some engineers relied upon mere bulk of masonry, others more skilfully disposed their material in a comparatively thin face wall with long counterforts, and others again had recourse to arched construction. The face of the wall was usually scarped or sloping at the lower part, and vertical at the upper part; but sometimes this was reversed to make shots ricochet, and to make escalade more difficult; sometimes, too, it was wholly vertical, and sometimes wholly inclined. The counter-forts, commonly vertical, were occasionally horizontal, serving as substitutes for the more perishable layers of brushwood in the rampart.
The narrow curtains of the old walls afforded no room for artillery, and the towers themselves were not well suited for it. If the guns were placed on the platforms of the towers, the space was very limited, and the vaults sometimes gave way: if they were placed in the floors below, the service was hindered by the smoke. High mounds were made for them inside the walls, where it could conveniently be done; but often the best place for them was in the bulwarks outside. Here they were able to flank the walls and give a reverse fire upon the breaches; and before long bulwarks began to be made with this special object, and placed at intervals suitable for it.
Sebastien'le Pretre de Vauban was born in 1633, at Vauban. St. Leger de Foucheret, near Avallon. His energy and talent induced Cardinal Mazarin to persuade him to enter the service of his sovereign, in which he continued till his death in 1707. He was created a Marshal of France in 1703. He repaired or constructed more than 160 places; took part in 48 sieges, 40 of which he directed as chief engineer, without a single failure; twice defended fortresses, and was present in more than 130 actions. The most remaikable changes introduced by him into the operations of military engineers related to the attack of fortresses. By systematising the whole process of attack he greatly reduced the duration of sieges, and increased the certainty of success. Vauban's later systems, or rather the tower-bastions which constituted their chief feature, did not find much favour among the French engineers, and were never applied after his death. But such was the prestige of his name, that it was thought better to bring forward new proposals as amendments in the details of his trace, than as rival systems. They exhibit the science of attack and defence nearly as it remained until the introduction of rifled weapons.
The system of defence initiated by Vauban developed with time and received an additional impulse by the invention of rifled artillery, which was first usod for a siege at Sebastopol in 1855-56. It may be considered to have culminated in the immense forts constructed for the defence of the fortress of Antwerp, which was begun in 1859, though this place has also a powerful enceinte.
The development of artillery which commenced in about the year 1879 ended the reign of the detached fort as the single means of defence, by necessitating the removal of at least part of its guns to intermediate batteries, and has at the same time given the final blow to the old enceinte as an essential part of a fortress. What became the type was a ring of redoubts, lines, and batteries, combined together so as to afford one another mutual support and assistance, but without any one work containing all the elements of defence in itself.
The new systems of defence proposed by Continental writers were very numerous. Almost all, however, appeared to be chiefly guided by the three following considerations: that works should be as little visible as possible; that cement concrete cannot be seriously injured by high-angle fire; that guns in cupolas will outlast a great deal of hammering, even if they may at last succumb. The intervals between the forts were proposed to be defended, in some cases, by open batteries; in others, with guns in cupolas, or on railway trucks carrying disappearing mountings, or the Royal Engineers wrote in 1892 "on trucks which are themselves armoured" - that is, a tank.
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