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Sapping is a term used in siege operations to describe the digging of a covered trench (a "sap") to approach a besieged place without danger from the enemy's fire. (verb) The purpose of the sap is usually to advance a besieging army's position towards an attacked fortification. It is excavated by specialised military units, whose members are often called
sapper A sapper, also called a combat engineer, is a combatant or soldier who performs a variety of military engineering duties, such as breaching fortifications, demolitions, bridge-building, laying or clearing minefields, preparing field defenses ...
s. By using the sap, the besiegers could move closer to the walls of a fortress, without exposing the sappers to direct fire from the defending force. To protect the sappers, trenches were usually dug at an angle in zig-zag pattern (to protect against enfilading fire from the defenders), and at the head of the sap a defensive shield made of
gabions A gabion (from Italian language, Italian ''gabbione'' meaning "big cage"; from Italian ''gabbia'' and Latin ''cavea'' meaning "cage") is a Cage (enclosure), cage, cylinder (geometry), cylinder or box filled with rocks, concrete, or sometimes s ...
(or a
mantlet In medieval warfare a mantlet or was a portable wall or shelter used for stopping projectiles. Some versions used wheels for enhanced mobility. A mantlet could protect one or several soldiers. In the First World War (1914-1918) French soldier ...
) could be deployed. Once the saps were close enough, siege engines or
cannon A cannon is a large-caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder during th ...
could be moved through the trenches to get closer to—and enable firing at—the fortification. The goal of firing is to batter a breach in the curtain walls, to allow attacking infantry to get past the walls. Prior to the invention of large pieces of
siege artillery Siege artillery (also siege guns or siege cannons) are heavy guns designed to bombard fortifications, cities, and other fixed targets. They are distinct from field artillery and are a class of siege weapon capable of firing heavy cannonballs or ...
, miners could start to tunnel from the head of a sap to undermine the walls. A fire or gunpowder would then be used to create a crater into which a section of the fortifications would fall, creating a breach. Before the development of explosives, sapping was the undermining of an enemy's fortifications, which would collapse when the sap's supports were removed. Later, explosives were placed surreptitiously in the undermining sap or mine, then detonated, as was done with 450 tons of high explosive in the First World War battle of Messines, the largest planned explosion until the 1945
Trinity atomic bomb test Trinity was the first detonation of a nuclear weapon, conducted by the United States Army at 5:29 a.m. MWT (11:29:21 GMT) on July 16, 1945, as part of the Manhattan Project. The test was of an implosion-design plutonium bomb, or "gadg ...
.


History


Pre-gunpowder

A way to force entry into a fortified structure was to dig a mine or sap under defensive walls, typically shored up by wooden props. On collapsing the tunnel, for example by burning the props, the wall would collapse.


1500s

Sapping trenches, cannons and gunpowder explosives were a potent force against fortifications. However, the
Siege of Godesberg The siege of Godesberg, 18 November – 17 December 1583, was the first major siege of the Cologne War (1583–1589). Seeking to wrest control of an important fortification, Bavarian and mercenary soldiers surrounded the Godesberg, and the vill ...
of 1583 during the
Cologne War The Cologne War (, ''Kölnischer Krieg'', '' Truchsessischer Krieg''; 1583–1588) was a conflict between Protestant and Catholic factions that devastated the Electorate of Cologne, a historical ecclesiastical principality of the Holy Roman Em ...
showed that fortresses could still withstand sapping and explosives to a point. After the attacking force of Ferdinand of Bavaria fired on the fortress with large caliber cannons; this had little impact on the walls. The cannons were firing heavy shot, but the height of the fortress significantly reduced the force of the impact with the walls, which bounced off to little effect, although the fortress dated from the 14th century. To breach the walls, Ferdinand ordered his soldiers to dig into the feldspar supporting the side of the mountain and place an explosive charge. Even after the powder was ignited and a substantial portion of the wall, the gate, and the inner walls were breached, the defenders still held out for three days.


''Trace Italienne'' forts

Sapping became necessary as a response to the development and spread of ''trace Italienne'' in defensive architecture in the 1500s. The Italian style star fort bastion made siege warfare and sapping the ''modus operandi'' of military operations in the late medieval and first decades of the early modern period of warfare. Fortresses with abutments with gentler angles were difficult to breach; cannonballs and mortar shells often had little impact on the walls, or impact that could be readily repaired after night fell. Towers no longer protruded at right angles from the wall; rather, they blended with the wall. These created a two-fold advantage. First, defenders in the towers had a field of fire of 280 degrees or more. This range of fire and the towers' positioning allowed defenders to fire upon the attackers' flank as they advanced, a deadly fire called
enfilade Enfilade and defilade are concepts in military tactics used to describe a military formation's exposure to enemy fire. A formation or position is "in enfilade" if weapon fire can be directed along its longest axis. A unit or position is "in de ...
. Consequently, a hostile force which ranged their cannons was less effective, as the "hostile cannon adto fire from longer range" and defenders could better enfilade attackers.


1600s

During the English Civil War, there was a siege of
Newark-on-Trent Newark-on-Trent () or Newark is a market town and civil parish in the Newark and Sherwood district in Nottinghamshire, England. It is on the River Trent, and was historically a major inland port. The A1 road (Great Britain), A1 road bypasses th ...
which took place from 6 March 1645 – 8 May 1646. A detailed map of the
Cavalier The term ''Cavalier'' () was first used by Roundheads as a term of abuse for the wealthier royalist supporters of Charles I of England and his son Charles II of England, Charles II during the English Civil War, the Interregnum (England), Int ...
s defences of Newark and the lines of
circumvallation Investment is the military process of surrounding an enemy fort (or town) with armed forces to prevent entry or escape. It serves both to cut communications with the outside world and to prevent supplies and reinforcements from being introduced ...
and
contravallation Investment is the military process of surrounding an enemy fort (or town) with armed forces to prevent entry or escape. It serves both to cut communications with the outside world and to prevent supplies and reinforcements from being introduced ...
along with the besiegers redoubts and fortified camps was drawn up by R Clampe, the besieging
Roundhead Roundheads were the supporters of the Parliament of England during the English Civil War (1642–1651). Also known as Parliamentarians, they fought against King Charles I of England and his supporters, known as the Cavaliers or Royalists, who ...
s' chief engineer. It includes a zig-zag sap emerging from a bastion of the circumvallation. The zig-zags are at such angles and positions that the defenders were unable to bring enfilade fire to bear. Once the sap was completed four cannons were placed much closer to a gateway than those in bastions of the circumvallation.


American Civil War

In the
American Civil War The American Civil War (April 12, 1861May 26, 1865; also known by Names of the American Civil War, other names) was a civil war in the United States between the Union (American Civil War), Union ("the North") and the Confederate States of A ...
, troops advanced their sap under cover of a sap roller or mantlet by forming a parapet on the engaged side of the trench one
gabion A gabion (from Italian ''gabbione'' meaning "big cage"; from Italian ''gabbia'' and Latin ''cavea'' meaning "cage") is a cage, cylinder or box filled with rocks, concrete, or sometimes sand and soil for use in civil engineering, road building ...
at a time and filling it with earth taken from the trench.


First World War

During First World War trench warfare, the combatant's sappers, who were often experienced civilian miners who had been rejected for combat duties due to age or ill-health, strived to undermine each other's positions, working silently to avoid detection. After completing a mine it was filled with explosives, sometimes hundreds of tons, and detonated, followed by an attack on the surprised survivors from the destroyed position.


Russian sap

A ''Russian sap'' is a tunnel dug at a shallow depth under no man's land towards an enemy position. It allows the attacking infantry to approach an enemy position without being detected and safe from enemy fire. For the attack, the tunnel is opened and the infantry attacks the enemy position at comparatively short range. Russian saps were widely used in the
First World War World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
, for example during the
Battle of the Somme The Battle of the Somme (; ), also known as the Somme offensive, was a battle of the First World War fought by the armies of the British Empire and the French Third Republic against the German Empire. It took place between 1 July and 18 Nove ...
, when four of them were further equipped with
Livens Large Gallery Flame Projector Livens Large Gallery Flame Projectors were large experimental flamethrowers used by the British Army in World War I, named after their inventor, Royal Engineers officer William Howard Livens. History Four Livens Large Gallery Flame Projectors wer ...
s. Similar tactics were used in the
Korean War The Korean War (25 June 1950 – 27 July 1953) was an armed conflict on the Korean Peninsula fought between North Korea (Democratic People's Republic of Korea; DPRK) and South Korea (Republic of Korea; ROK) and their allies. North Korea was s ...
by the Chinese
People's Volunteer Army The People's Volunteer Army (PVA), officially the Chinese People's Volunteers (CPV), was the armed expeditionary forces China in the Korean War, deployed by the History of the People's Republic of China (1949–1976), People's Republic of Chi ...
, when they dug under the
Yalu River The Yalu River () or Amnok River () is a river on the border between China and North Korea. Together with the Tumen River to its east, and a small portion of Paektu Mountain, the Yalu forms the border between China and North Korea. Its valle ...
to attack US troops, and by
Hamas The Islamic Resistance Movement, abbreviated Hamas (the Arabic acronym from ), is a Palestinian nationalist Sunni Islam, Sunni Islamism, Islamist political organisation with a military wing, the Qassam Brigades. It has Gaza Strip under Hama ...
, when carrying out tunnel warfare from the Gaza Strip against
Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...
.


See also

*
Mining (military) Tunnel warfare refers to aspects of War, warfare relating to Tunnel, tunnels and other underground cavities. It includes the construction of underground facilities in order to attack or defend, and the use of existing natural caves and arti ...


References

;Notes ;Bibliography * * *


External links


The Civil War Field Fortifications Website
{{Man-made and man-related Subterranea Military engineering