field fortification

(′fēld förd·ə·fə′kā·shən)

(ordnance) Fortification constructed in the field to strengthen the natural defenses of the ground features, including foxholes, obstacles, trenches, gun emplacements, and so forth.

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Field fortification is designed to provide defence against a tactical threat expected to be of limited duration. It is commonly used by troops intending to hold a position against an advancing enemy, by rearguards covering a retreat, or by advanced parties while they wait to be reinforced. The term also covers the works constructed to defend camps and isolated posts, as well as those used for the protection of those besieging a fortress. The components are therefore basic materials that can be quickly put into place by the use of simple tools and as easily dismantled or abandoned when no longer needed. Some systems and methods have remained virtually unchanged from the beginning of organized warfare until the present day.

The most elementary field fortification is a ditch, which in itself will impede the progress of an enemy. Throwing the excavated soil behind it doubles the height of the obstacle the attacker has to cross, while at the same time providing a rampart for the protection of the defenders. Where the protection required is against missile rather than shock action, the ditch can be occupied for use as a trench, and part of the excavated material thrown in front of it, to serve as a parapet over which the defenders can shoot. The soil behind them then becomes a parados, so that the heads of entrenched defenders do not appear in silhouette against a background. An even simpler form of excavated field fortification is the pit. If intended for occupation, it gives the defender cover from fire and view. An alternative purpose is to act as a trou de loup, with the bottom of the pit containing a sharpened stake, and the top concealed by vegetation. More sophisticated field works can be built using earth in containers such as, in modern times, sandbags or oil drums, or, in earlier periods, wicker gabions (cylindrical open baskets). In the 1990s a modern version—‘bastion walling’ invented by an unemployed British miner—used wire mesh and ‘geo-textile’ to form the basket. It was extensively used in the Gulf and Bosnia.

'Digging in' is a prominent part of every soldier's life. Field fortifications can significantly slow the enemy's progress. In ancient times field fortifications were widely used in siege warfare — like Julius Caesar's fortifications at Alesia — and in the field. The appearance of rifled small arms in the mid-19th century was accompanied by a revival of digging. The future war theorist Ivan Bloch correctly noted, in 1898, that in future the spade would be as essential to the soldier as his rifle. He was not wrong
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Revetments to keep the earth in place were generally constructed of local timber, hurdles, turf, and similar natural materials, supplemented from the late 19th century onwards by sheets of corrugated iron. Abatis are made up of trees and bushes, felled with their branches pointing away from the position to be fortified, and their trunks secured in position by ropes and stakes. In desert regions, the corresponding form of field fortification is the zariba, an enclosure protected by thorn bushes. In rocky terrain, where digging is difficult, boulders are used to build sangars, which serve the same purpose. Inundations are formed by blocking up streams and sluices so as to flood the surrounding areas. Palisades consist of stakes planted upright and fastened together to form a fence. Roman legionaries each carried a stake with which to form the palisade of the camp they constructed at the end of each day's march when on campaign. In the medieval period, archers similarly carried a stake to protect their position against cavalry. Fraises are sharp stakes placed as near to the horizontal as possible in the side of steep slopes. Slopes and ditches may also be lined with flints, broken glass, agricultural harrows, and similar pointed or sharp-edged objects. Chevaux de frise (‘horses of Friesland’) are made by fastening stakes or metal spikes to a heavy beam, at right angles to each other. In modern French, the term has come to be used for portable barbed wire entanglements. Barbed wire first made its appearance on the battlefield during the American civil war. Barricades, used to block a street or bridge, can be made of any easily assembled material, wheeled vehicles, industrial containers, furniture, rubble, etc. Caltrops or crows'-feet, made of four spikes joined so that one always points upwards, were an effective protection against cavalry in the field and were also used at fords where infantry were expected to cross. They were a precursor to modern mines, high-explosive devices that can be detonated by the completion of an electrical circuit, by pressure, or by a tripwire. The earliest explosive mines took the form of fougasses, buried gunpowder charges sprung by the defenders when the need arose.

If sufficient labour, time, and materials were available, larger field fortifications such as redoubts (miniature forts open at the back, capable of holding both artillery and infantry), could be constructed and sited to support the main battle line. Domestic buildings in the right place could be fortified by having their walls pierced by loopholes, their floors either removed or strengthened, and their doors and windows blocked. Ideally, thatch roofing and other combustibles were removed. Both at the farm of Hougoumont in the battle of Waterloo and at the mission station of Rorke's Drift in the Zulu war, the position of the British defenders was threatened when the thatch caught fire. Fortified domestic buildings reappeared in Bosnia in the 1990s where stout timber walls filled with gravel proved effective temporary fortifications. Stockades, walls of stout timber uprights, disappeared from European battlefields with the advent of field artillery but continued in North American and colonial campaigns, where they provided protection against ill-armed native opponents. Blockhouses, isolated defence works with roofed accommodation for a small garrison, were also used most characteristically in colonial warfare. In siege warfare, field fortifications of various types protected the besiegers against sallies by the garrison, and sheltered them as they began their approach to the walls. Although not intended as permanent features, some field fortifications remain visible long after their military purpose no longer exists. Among the oldest of these is the legionary camp built for the siege of Masada in Roman Judaea (now Israel). The most impressive include the Lines of Torres Vedras, constructed by Wellington's engineers in 1810 to stop the French from reaching Lisbon. In France, sections of the complicated field defences that played so important a part in the positional warfare of the western front from 1914 to 1918 are deliberately preserved. During the decades after WW I, ‘in the trenches’ was used as a synonym for warfare itself.

Bibliography

• Duffy, Christopher, Siege Warfare (London, 1979).
• Lewis, J. F. (ed.), Text Book of Fortification and Military Engineering (London, 1892).
• Muller, John, The Attack and Defence of Fortified Places (London, 1791)

— Tony Heathcote