Breach

Breach, in a military sense, is a gap or opening in any of the defences of a fortress, effected either by mining or by the fire of guns placed in what are called 'breaching-batteries.' The high earthen ramparts of all fortresses are surrounded by deep ditches. In order to support the weight of the rampart, and make the ditch a more formidable obstacle, its sides are built up with retaining walls of masonry, technically called 'revetments,' often 30 feet high and 15 feet thick at the foot. To breach by mining, the explosives are lodged at the back of the revetment and near its foot under the parapet in sufficient quantities to bring down the greater part of the whole bank of earth and retaining wall. The debris falling into the ditch forms a ramp or slope, up which the assaulting party rush into the fortress. At the same time the wall retaining the far side of the ditch, called the 'counterscarp,' is treated in a similar manner to facilitate the descent into the ditch. The same result may be obtained by artillery fire. Heavy howitzers are placed in batteries about 1000 yards from the 'escarp' or revetment of the rampart, upon which they drop shell, at an angle of descent of about 14°, crumbling it away from the top downwards, until a practical breach 20 or 40 yards wide is made. During the Peninsular war there were some formidable examples of breaching. At Badajoz, 14,000 shot brought down 180 feet of wall in 104 hours, from a distance of 450 yards. At St Sebastian, 13,000 shot brought down 100 feet of wall in 62 days, from a distance of 620 yards. It was then calculated that 10,000 24-lb. shot, or 240,000 lb. of iron, would breach 100 feet of wall of average dimensions from a distance of 500 yards. But improvements in modern artillery have greatly reduced these figures; thus, at the siege of Strasburg in 1870, 1000 rounds from a 60-pounder gun brought down 30 yards of a wall 15 feet high from a battery 870 yards distant. See SIEGE.