The New Student's Reference Work/Fortification

For'tifica'tion is the military art of strengthening a place against the attack of troops. There are two branches, called field and permanent fortification. Field-fortification includes such slight intrenchments and field-defenses as can be thrown up by the troops themselves during the few hours before a battle, as well as fieldworks requiring days or weeks to build. Permanent fortification deals with engineering works for the defense of points of importance. Years may be spent in finishing them, and iron and masonry are largely used in building them. Field-fortification, while aiming at giving the defenders of a chosen position all the advantages of cover from the enemy's fire and of forcing him to advance over open ground swept by their fire, must also allow free movement for countercharges. A position is made ready for attack by loopholing any buildings, which may stand on it, and the walls around them, strengthening the cover afforded by ditches and hedges along the front or by throwing up breastworks and digging rifle-pits, with deep trenches in the rear for supports and gun-pits for artillery. Parts of this line should be so placed as to flank an attack on the front, and no cover should be left for the enemy during his advance. Hollows, which cannot be seen from the front, should be filled with brushwood. To oppose the advance of the enemy an abattis is often used. This is a row of tree-branches, sharpened and laid with points outward. Entanglements are also used; either of brushwood cut halfway through and woven together with wire run through it or of several lines of barbed wire fastened to stakes. Only the more important points of such a position are really fortified by building field-redoubts, usually in the form of a square, forming strong points in the main line, advanced posts in its front or a second line of works in the rear. Often redoubts have only two sides meeting at a point in front; or they may be five-sided—two in front called the faces, two on the flanks and in the rear a lower side called the gorge. The faces and flanks are formed by parapets (meaning "guard the breast"), twelve to sixteen feet thick, to resist artillery. The gorge is shut in usually by a light parapet, say three feet thick, or by a stockade (a wall of bullet-proof timber). In building a redoubt a ditch is made in front. Sometimes sharp palings, called palisades, are planted in the bottom. The top or crest of the parapet is never more than twelve feet above the ground in a field-redoubt. Fieldworks of this kind can be built in from eighteen to twenty-four hours, and are able to withstand the fire of field-guns. Blockhouses are now only used in mountain-warfare, where artillery could not be used and timber is plentiful.

Permanent fortification, for the defense of cities, harbors, tracts of country, bridges, roads and the like goes back to the earliest times. Its aim formerly was to keep out the enemy, unaccompanied by counterattacks, except sorties to destroy siege-works and batteries. Since 1859 detached works and free maneuvering ground between them for counter-attack have been used for permanent works as well as for field-intrenchments. This is due to the great improvement in artillery and small arms, cannon easily destroying the strongest works at long range and the breech-loading rifle increasing the power of armies in the open field.

In Greek history we read of cities surrounded with walls of brick, stone and rubble. Babylon had a wall of enormous length, 100 feet high and 32 feet thick, surmounted by towers. Jerusalem at the time of Vespasian's siege had like walls. But the square and round towers which had been defense enough against arrows, and the walls which had withstood battering rams, were soon found to be useless against cannon. Early in the i5th century the Italians began to flank their walls with bastions (built like the outer faces of a redoubt). This form of defense was carried to great perfection by the great Vauban, the engineer of Louis XIV. He built 33 new fortresses, improved over one hundred and himeslf carried on more than fifty sieges. Vauban's forts were in the shape of a polygon. The main body of the place is called the enceinte. Bastions are built out, and joined by a parapet called a curtain. A rampart is formed of the earth dug from the ditch, and a parapet is built on it. To protect the flanks an outwork on the far side of the main ditch is built, called the ravelin. As cannon became more powerful, the masonry had to be covered

by what are called counter-guards. The enceinte or main fortification at Antwerp is a good example of the best modern modification of the old system of Vauban. The fortifications at Antwerp also show how the science has changed, outworks close to the enceinte being replaced by a chain of detached forts three to five miles from it. At Antwerp the forts are about a mile and a quarter apart and two to three miles in front. Each has 700 yards of front, 120 guns, 15 mortars and a garrison of 1,000 men. They are in the shape of square redoubts. If attacked, supporting batteries would be thrown up between them, and, before the main fortress can be reached, at least two must be captured, which would be very difficult in the face of an army which could be gathered in the 200 square miles shut in by the chain of forts. These forts are joined by a circular railroad. Since the war of 1870 the whole of France has been fortified in this way, making it a camp-fortress, as the Austrians say.

A seaport or dockyard must be fortified in a different way from an inland town, as the heaviest guns can be brought against it by the enemy's ships, and it can now be bombarded at a distance of ten or more miles. The first line of defense is made of submarine mines. To protect these, shore batteries are thrown up, able to drive back a landing party. Electric lights to discover the position of the enemy, guard-boats, swift steamers to scout in front and torpedo-boats are necessary. For the real defense the heaviest guns to be had are mounted. See Military Engineering by Prof. D. H. Mahan.