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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.
A circumvallation is a line of fortifications, built by the attackers around the besieged fortification facing towards an enemy fort to protect the besiegers from sorties by its defenders and to enhance the blockade. [ citation needed ] Lines of circumvallation generally consist of earthen ramparts and entrenchments that encircle the besieged city. The line of circumvallation can be used as a base to launch assaults against the besieged city or to construct further earthworks nearer to the city.The resulting fortifications are known as "lines of circumvallation".
A contravallation may be constructed if the besieging army is threatened by a field army allied to an enemy fort.It is a second line of fortifications outside the circumvallation that faces away from an enemy fort. The contravallation protects the besiegers from attacks by allies of the city's defenders and enhances the blockade of an enemy fort by making it more difficult to smuggle in supplies.
Thucydides notes the role circumvallation played in the Sicilian Expedition and in the Spartan siege of Plataea during the initial stages of the Peloponnesian War in 429 BC.
Julius Caesar in his Commentaries on the Gallic War describes his textbook use of the circumvallation and contravallation to defeat the Gauls under their chieftain, Vercingetorix, at the Siege of Alesia in September 52 BC.
Another example from the pre-modern period is the siege of Siege of Constantinople (717–718).
The caliph of the Umayyad Empire took advantage of the violent anarchy in the Byzantine Empire to prepare a huge host, comprising more than 100,000 troops and 1,800 ships, to take them to the Byzantine capital, Constantinople. Upon arriving outside the city's Theodosian walls, the Arab host had some knowledge that Emperor Leo III the Isaurian had allied with Bulgaria under Khan Tervel, and so, in preparation for the Bulgarian army, built a set of stone walls against the city and against the countryside, with the Arab camp in between.
King Pepin the Short of Francia built a number of fortified camps during his Siege of Bourbon (761) to surround the town completely.He built a complete set of lines of circumvallation and contravallation during the Siege of Bourges (762).
The basic objectives and tactics of a military investment have remained the same in the modern era. During the Second World War, there were many sieges and many investments. One of the best-known sieges of the war, which demonstrated the tactical use of investment, was the Siege of Stalingrad. During the first half of the siege, the Germans were unable to fully encircle the city and so the Soviets got men and supplies in across the Volga River. During the second half of the battle, the complete investment of Stalingrad by the Soviets, including airspace, which prevented the construction by the Germans of an adequately large airbridge, eventually forced the starving Germans in the city to surrender.
In modern times, investments and sieges of cities are often combined with intensive shelling and air strikes.
A siege is a military blockade of a city, or fortress, with the intent of conquering by attrition, or a well-prepared assault. This derives from Latin: sedere, lit. 'to sit'. Siege warfare is a form of constant, low-intensity conflict characterized by one party holding a strong, static, defensive position. Consequently, an opportunity for negotiation between combatants is not uncommon, as proximity and fluctuating advantage can encourage diplomacy. The art of conducting and resisting sieges is called siege warfare, siegecraft, or poliorcetics.
The Battle of Alesia or Siege of Alesia was a military engagement in the Gallic Wars around the Gallic oppidum of Alesia in modern France, a major centre of the Mandubii tribe. It was fought by the Roman army of Julius Caesar against a confederation of Gallic tribes united under the leadership of Vercingetorix of the Arverni. It was the last major engagement between Gauls and Romans, and is considered one of Caesar's greatest military achievements and a classic example of siege warfare and investment; the Roman army built dual lines of fortifications—an inner wall to keep the besieged Gauls in, and an outer wall to keep the Gallic relief force out. The Battle of Alesia marked the end of Gallic independence in modern day territory of France and Belgium.
The siege of La Rochelle was a result of a war between the French royal forces of Louis XIII of France and the Huguenots of La Rochelle in 1627–28. The siege marked the height of the struggle between the Catholics and the Protestants in France, and ended with a complete victory for King Louis XIII and the Catholics.
Encirclement is a military term for the situation when a force or target is isolated and surrounded by enemy forces. The situation is highly dangerous for the encircled force. At the strategic level, it cannot receive supplies or reinforcements, and on the tactical level, the units in the force can be subject to an attack from several sides. Lastly, since the force cannot retreat, unless it is relieved or can break out, it must fight to the death or surrender.
A sally port is a secure, controlled entry way to an enclosure, e.g., a fortification or prison. The entrance is usually protected by some means, such as a fixed wall on the outside, parallel to the door, which must be circumvented to enter and prevents direct enemy fire from a distance. It may include two sets of doors that can be barred independently to further delay enemy penetration.
A redoubt is a fort or fort system usually consisting of an enclosed defensive emplacement outside a larger fort, usually relying on earthworks, although some are constructed of stone or brick. It is meant to protect soldiers outside the main defensive line and can be a permanent structure or a hastily constructed temporary fortification. The word means "a place of retreat". Redoubts were a component of the military strategies of most European empires during the colonial era, especially in the outer works of Vauban-style fortresses made popular during the 17th century, although the concept of redoubts has existed since medieval times. A redoubt differs from a redan in that the redan is open in the rear, whereas the redoubt was considered an enclosed work.
A bastion fort or trace italienne is a fortification in a style that evolved during the early modern period of gunpowder when the cannon came to dominate the battlefield. It was first seen in the mid-fifteenth century in Italy. Some types, especially when combined with ravelins and other outworks, resembled the related star fort of the same era.
The Three Cities is a collective description of the three fortified cities of Birgu, Senglea and Cospicua in Malta. The oldest of the Three Cities is Birgu, which has existed since prior to the Middle Ages. The other two cities, Senglea and Cospicua, were both founded by the Order of Saint John in the 16th and 17th centuries. The Three Cities are enclosed by the Cottonera Lines, along with several other fortifications. The term Cottonera is synonymous with the Three Cities, although it is sometimes taken to also include the nearby town of Kalkara.
Vallum is either the whole or a portion of the fortifications of a Roman camp. The vallum usually comprised an earthen or turf rampart (Agger) with a wooden palisade on top, with a deep outer ditch (fossa). The name is derived from vallus, and properly means the palisade which ran along the outer edge of the top of the agger, but is usually used to refer to the whole fortification.
The siege of Maastricht was fought between 9 June and 22 August 1632, when the Dutch commander Frederick Henry, Prince of Orange, eventually captured the city from Habsburg forces.
The siege of Carlisle occurred during the First English Civil War when the allied forces of the Scottish Covenanters and the English Parliamentarians besieged Carlisle Castle which was held at the time by the English Royalist forces loyal to King Charles I. The siege took place in Carlisle, Cumbria from October 1644 to 25 June 1645.
Sapping is a term used in siege operations to describe the digging of a covered trench to approach a besieged place without danger from the enemy's fire. 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 sappers.
The siege of Grol in 1627 was a battle between the Army of the Dutch Republic, commanded by Frederick Henry, Prince of Orange, and the Spanish-controlled fortified city of Grol, during the Eighty Years War and the Anglo–Spanish War in 1627. The Spanish Army, led by Hendrik van den Bergh, came to relieve Grol but too late. The siege lasted from 20 July until 19 August 1627, resulting in the surrender of the city to the Dutch army.
The fifth siege of Breda was an important siege in the Eighty Years' War in which stadtholder Frederick Henry, Prince of Orange retook the city of Breda, which had last changed hands in 1625 when the Spanish general Ambrogio Spinola conquered it for the Spanish Habsburgs. Hereafter, the city would remain in the hands of the Dutch Republic until the end of the war.
The fortified region of Belfort(place fortifiée de Belfort) formed the first line of defense in the Séré de Rivières system of fortifications in the Belfort Gap. Located in northeastern France between Épinal and Besançon, the primary line was built in the late 19th century to deal with advances in artillery that had made older defensive systems obsolete.
The fourth siege of Badajoz took place from July to October 1658 during the Portuguese Restoration War. It was an attempt by a huge Portuguese army under the command of Joanne Mendes de Vasconcelos, governor of Alentejo, to capture the Spanish city of Badajoz, which was the headquarters of the Spanish Army of Extremadura. The fortifications of Badajoz were essentially medieval and considered vulnerable by the Portuguese, and had already been attacked by them three times during this war.
The Siege of Dunkirk in 1658 was a military operation by the allied forces of France and Commonwealth England intended to take the fortified port city of Dunkirk, Spain's greatest privateer base, from the Spanish and their confederates: the English royalists and French Fronduers. Dunkirk was a strategic port on the southern coast of the English Channel in the Spanish Netherlands that had often been a point of contention previously and had changed hands a number of times. Privateers operating out of Dunkirk and other ports had cost England some 1,500 to 2,000 merchant ships in the past year. The French and their English Commonwealth allies were commanded by Marshal of France Turenne. The siege would last a month and featured numerous sorties by the garrison and a determined relief attempt by the Spanish army under the command of Don Juan of Austria and his confederate English royalists under Duke of York and rebels of the French Fronde under the Great Condé that resulted in the battle of the Dunes.
Counter-castles were built in the Middle Ages to counter the power of a hostile neighbour or as a siege castle, that is, a fortified base from which attacks could be launched on a nearby enemy castle.
The Siege of Bourges was a Frankish siege of the Aquitanian fortress town of Bourges in 762 during the Aquitanian War. The Frankish army under King Pepin the Short invested the fort with lines of circumvallation, contravallation and siege engines. The walls were breached and the fort taken. Count Chunibert of Bourges swore his loyalty to Pepin along with his Gascon levies and their families. Pepin appointed several counts of his own to garrison the place and the Frankish army went on to besiege Thouars.