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Siege

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Siege of ConstantinopleEnlarge

Siege of Constantinople

(painted 1499)]]

A siege is a prolonged military assault on and blockade of a city or fortress with the intent of conquering by force or attrition. A siege occurs when an attacker encounters a city or fortress that refuses to surrender and cannot be easily taken by a frontal assault. Sieges usually involve surrounding the target and blocking the provision of supplies, typically coupled with artillery bombardment, sapping and mining to reduce fortifications.

Sieges are as old as warfare itself, with towns in the Middle East from the dawn of civilization having city walls. During the Renaissance and the Early Modern period, siege warfare dominated the conduct of war in Europe. Leonardo da Vinci gained as much of his renown from the design of fortifications as from his artwork.

Campaigns were generally designed around a succession of sieges. It was not until the Napoleonic period when dynamic striking columns forced armies into the field and the ever increasing use of, ever more powerful, cannon reduced the value of fortifications. In modern times, trenches replaced walls, and bunkers replaced castles. In the 20th century, the significance of the classical siege has declined. With the advent of mobile warfare, one single fortified stronghold is no longer as decisive as it once was. While sieges do still occur, they are not as common as they once were due to changes in modes of battle, principally the ease by which huge volumes of destructive power can be directed onto a static target.

Table of contents
1 Ancient and medieval siege warfare
2 Mongol siege warfare
3 Sieges in the age of gunpowder
4 Modern warfare
5 Police actions
6 See also
7 References
8 Further reading
9 External links

Ancient and medieval siege warfare

[[TrebuchetEnlarge

[[Trebuchet

at Château des Baux in France.]]

Ancient sources contain many stories of sieges, such as the siege of Jericho in the Old Testament or the siege of Troy described by Homer in the Iliad. An astonishing number and variety of sieges formed the core of Julius Caesar's conquest of Gaul.

The universal method for defending against siege is the use of fortifications, principally walls and ditches. A sufficient supply of food and water is also important to defeat the simplest method of siege warfare: starvation. During a siege, a surrounding army would build earthworks (a line of circumvallation) to completely encircle their target, preventing food and water supplies from reaching the besieged city. If sufficiently desperate as the siege progressed, defenders and civilians might have been reduced to eating anything vaguely edible—horses, family pets, the leather from shoes, and even each other. On occasion, the defenders would drive 'surplus' civilians out to reduce the demands on stored food and water.

To prevent a relief force from breaking the siege, the attackers would also construct a second series of earthworks (a line of contravallation), creating a double ring around the beseiged city. This was immense and expensive work but very likely to succeed, provided no other force intervened.

Disease was another effective siege weapon, although the attackers were often as vulnerable as the defenders.

To end a siege more rapidly various methods were developed in ancient and medieval times to counter fortifications, and a large variety of siege engines were developed for use by besieging armies. Ladders could be used to escalade over the defenses. Battering rams could be used to force through gates or walls, while catapults, ballistae, trebuchets, mangonels, and onagers could be used to launch projectiles in order to break down a city's fortifications and kill its defenders. A siege tower could also be used: a substantial structure built as high, or higher than the walls, it allowed the attackers to fire down upon the defenders and also advance troops to the wall with less danger than using ladders.

In addition to launching projectiles at the fortifications or defenders, it was also quite common to attempt to undermine the fortifications, causing them to collapse. This could be accomplished by digging a tunnel beneath the foundations of the walls, and then deliberately collapsing or exploding the tunnel. This process is known as sapping or mining. The defenders could dig counter-tunnels to cut into the attacks works and collapse them prematurely.

Fire was often used as a weapon when dealing with wooden fortifications. In ancient Japan, where buildings used to store supplies were mostly wooden, a fire could drive opponent to a starvation. The Byzantine Empire invented Greek fire, which contained additives that made it hard to put out. Combined with a primitive flamethrower, it proved an effective offensive and defensive weapon.

[[Cahir CastleEnlarge

[[Cahir Castle

in Ireland was besieged and captured three times: in 1599 by the Earl of Essex, in 1647 by Lord Inchiquin, and in 1650 by Oliver Cromwell.]]

Advances in the prosecution of sieges in ancient and medieval times naturally encouraged the development of a variety of defensive counter-measures. In particular, medieval fortifications became progressively stronger—for example, the advent of the concentric castle from the period of the Crusades—and more dangerous to attackers—witness the increasing use of machiolations and murder-holes, as well the preparation of boiling oil, molten lead or hot sand. Arrow slits, concealed doors for sallies, and deep water wells were also integral means of resisting siege at this time. Particular attention would be paid to defending entrances, with gates protected by drawbridges, portcullises and barbicans. moats and other water defenses, whether natural or augmented, were also vital to defenders.

In the European Middle Ages, virtually all large cities had city walls—Dubrovnik in Dalmatia is an impressive and well-preserved example—and more important cities had citadels, forts or castles. Great effort was expended to ensure a good water supply inside the city in case of siege. In some cases, long tunnels were constructed to carry water into the city. Complex systems of underground tunnels were used for storage and communications in medieval cities like Tábor in Bohemia (similar to those used much later in Vietnam during the Vietnam War).

Until the invention of gunpowder-based weapons (and the resulting higher-velocity projectiles), the balance of power and logistics definitely favored the defender. With the invention of gunpowder, cannon and (in modern times) mortarss and howitzers, the traditional methods of defense became less and less effective against a determined siege.

Mongol siege warfare

In the Middle Ages, the Mongol Empire's campaign against China by Genghis Khan and his army was extremely effective, allowing the Mongol hordes to sweep through large areas. Even if they could not enter some of the more well-fortified cities, they used innovative battle tactics to grab hold of the land and the people:

"By concentrating on the field armies, the strongholds had to wait. Of course, smaller fortresses, or ones easily surprised, were taken as they came along. This had two effects. First, it cut off the principal city from communicating with other cities where they might expect aid. Secondly, refugees from these smaller cities would flee to the last stronghold. The reports from these cities and the streaming hordes of refugees not only reduced the morale of the inhabitants and garrison of the principle city, it also strained their resources. Food and water reserves were taxed by the sudden influx of refugees. Soon, what was once a formidable undertaking became easy. The Mongols were then free to lay siege without interference of the field army as it had been destroyed... At the siege of Aleppo, Hulegu used twenty catapults against the Bab al-Iraq (Gate of Iraq) alone. In Jûzjânî, there are several episodes in which the Mongols constructed hundreds of siege machines in order to surpass the number which the defending city possessed. While Jûzjânî surely exaggerated, the improbably high numbers which he used for both the Mongols and the defenders do give one a sense of the large numbers of machines used at a single siege." 1

Another Mongol tactic was to use catapults to launch corpses of plague victims into besieged cities. The disease-carrying fleas from the person's body would then infest the city, and the plague would spread allowing the city to be easily captured, although this transmission mechanism was not known at the time.

On the first night while sieging a city, the leader of the Mongol forces would lead from a white tent: if the city surrendered, all would be spared. On the second day, he would use a red tent: if the city surrendered, the men would all be killed, but the rest would be spared. On the third day, he would use a black tent: no quarter would be given.

This attitude was common to most armies. A city that surrendered could expect to negotiate terms to avoid a sack. A city broken by siege or assault could suffer extreme retribution, even in the 19th century.

Sieges in the age of gunpowder

The introduction of gunpowder and the use of siege cannons brought about a new age in siege warfare. Cannon were first used in the early 13th century, they did not become significant weapons for another 150 years or so. By the 16th century, they were an essential and regularized part of any campaigning army, or castle's defences.

The greatest advantage of cannons over other siege weapons was the ability to fire a heavier projectile, further, faster and more often than previous weapons. Thus, 'old fashioned' walls—that is high and, relatively, thin—were excellent targets and, over time, easily demolished. In 1453, the great walls of Constantinople were broken through in just six weeks by the 62 cannon of Mehmet II's army.

However new fortifications, designed to withstand gunpowder weapons, were soon constructed throughout Europe. During the Renaissance and the Early Modern period, siege warfare continued to dominate the conduct of war in Europe.

Emerging theories on improving fortifications

The castles that in earlier years had been formidable obstacles were easily breached by the new weapons. For example, in Spain, the newly equipped army of Ferdinand and Isabella was able to conquer Moorish strongholds in Granada in 1482–92 that had held out for centuries before the invention of cannons.

In the early 15th century, Italian architect Leon Battista Alberti wrote a treatise entitled De Re aedificatoria which theorized methods of building fortifications capable of withstanding the new guns. He proposed that walls be "built in uneven lines, like the teeth of a saw." He proposed star-shaped fortresses with low thick walls.

However, few rulers paid any attention to his theories. A few towns in Italy began building in the new style late in the 1480s, but it was only with the French invasion of the Italian peninsula in 1494–95 that the new fortifications were built on a large scale. Charles VIII invaded Italy with an army of 18,000 men and a horse-drawn siege-train. As a result he could defeat virtually any city or state, no matter how well defended. In a panic, military strategy was completely rethought throughout the Italian states of the time, with a strong emphasis on the new fortifications that could withstand a modern siege.

New styles of fortresses employed

The most effective way to protect walls against cannon fire proved to be depth (increasing the width of the defences) and angles (ensuring that attackers could only fire on walls at an oblique angle, not square on). Initially walls were lowered and baked, in front and behind, with earth. Towers were reformed into triangular bastions.

This design matured into the trace italienne. Star-shaped fortresses surrounding towns and even cities with outlying defenses proved very difficult to capture, even for a well equipped army. Fortresses built in this style throughout the 16th century did not become fully obsolete until the 19th century, and were still in use throughout World War I (though modified for 20th century warfare).

However, the cost of building such vast modern fortifications was incredibly high, and was often too much for individual cities to undertake. Many were bankrupted in the process of building them; others, such as Siena, spent so much money on fortifications that they were unable to maintain their armies properly, and so lost their wars anyway. Nonetheless, innumerable large and impressive fortresses were built throughout northern Italy in the first decades of the 16th century to resist repeated French invasions that became known as the Wars of Italy. Many stand to this day.

In the 1530s and 1540s, the new style of fortification began to spread out of Italy into the rest of Europe, particularly to France, the Netherlands, and Spain. Italian engineers were in enormous demand throughout Europe, especially in war-torn areas such as the Netherlands, which became dotted by towns encircled in modern fortifications. For many years, defensive and offensive tactics were well balanced leading to protracted and costly wars such as Europe had never known, involving more and more planning and government involvement.

The new fortresses ensured that war rarely extended beyond a series of sieges. Because the new fortresses could easily hold 10,000 men, an attacking army could not ignore a powerfully fortified position without serious risk of counterattack. As a result, virtually all towns had to be taken, and that was usually a long drawn out affair, potentially lasting from several months to years, while the members of the town were starved to death. Most battles in this period were between besieging armies and relief columns sent to rescue the besieged.

Marshall Vauban

A pentagonal Vauban fortressEnlarge

A pentagonal Vauban fortress

At the end of the 17th century, Marshal Vauban, a French military engineer, developed modern fortification to its pinnacle, refining siege warfare without fundamentally altering it: ditches would be dug; walls would be protected by glacis; and bastions would enfilade an attacker. He was also a master of planning sieges themselves. Before Vauban, sieges had been somewhat slapdash operations. Vauban refined besieging to a science with a methodical process that, if uninterrupted, would break even the strongest fortifications.

Planning and maintaining a siege is just as difficult as fending one off. A besieging army must be prepared to repel both sorties from the besieged area and also any attack that may try to relieve the defenders. It was thus usual to construct lines of trenches and defenses facing in both directions. The outermost lines, known as the lines of circumvallation, would surround the entire besieging army and protect it from attackers. This would be the first construction effort of a besieging army, built soon after a fortress or city had been invested. A line of contravallation would also be constructed, facing in towards the besieged area, to protect against sorties by the defenders and to prevent the besieged from escaping.

The next line, which Vauban usually placed at about 600 meters from the target, would contain the main batteries of heavy cannons so that they could hit the target without being vulnerable themselves. Once this line was established, work crews would move forward creating another line at 250 meters. This line contained smaller guns. The final line would be constructed only 30 to 60 meters from the fortress. This line would contain the mortars and would act as a staging area for attack parties once the walls were breached. It would also be from there that sappers working to undermine the fortress would operate.

The trenches connecting the various lines of the besiegers could not be built perpendicular to the walls of the fortress, as the defenders would have a clear line of fire along the whole trench. Thus, these lines (known as saps) needed to be sharply jagged.

Another element of a fortress was the citadel. Usually a citadel was a "mini fortress" within the larger fortress, sometimes designed as a last bastion of defense, but more often as a means of protecting the garrison from potential revolt in the city. The citadel was used in wartime and peacetime to keep the residents of the city in line.

As in ages past, most sieges were decided with very little fighting between the opposing armies. An attacker's army was poorly served incurring the high casualties that a direct assault on a fortress would entail. Usually they would wait until supplies inside the fortifications were exhausted or disease had weakened the defenders to the point that they were willing to surrender. At the same time, diseases, especially typhus were a constant danger to the encamped armies outside the fortress, and often forced a premature retreat. Sieges were often won by the army that lasted the longest.

An important element of strategy for the besieging army was whether or not to allow the encamped city to surrender. Usually it was preferable to graciously allow a surrender, both to save on casualties, and to set an example for future defending cities. A city that was allowed to surrender with minimal loss of life was much better off than a city that held out for a long time and was brutally butchered at the end. However, if an attacking army had a reputation of killing and pillaging regardless of a surrender, then other cities' defensive efforts would be redoubled.

Advent of mobile warfare

Siege warfare dominated in Western Europe for most of the seventeenth and eighteenth centuries. An entire campaign, or longer, could be used in a single siege (for example, Ostend in 1601–04; La Rochelle in 1627–28). This resulted in extremely elongated conflicts. The balance was that while siege warfare was extremely expensive and very slow, it was very successful—or, at least, more so than encounters in the field. Battles arose through clashes between besiegers and punative relieving armies, but the prinicple was a slow grinding victory by the greater economic power. The relatively rare attempts at forcing pitched battles (Gustavus Adolphus in 1630; the French against the Dutch in 1672 or 1688) were almost always expensive failures.

However, this pattern was eradicated by the French Revolutionary and Napoleonic Wars. New techniques stressed rapidly moving armies that would clash on the open field of battle, and one single fortified stronghold was no longer as decisive as it used to be. Advances in artillery made previously impregnable defenses useless. For example, the walls of Vienna that had held off the Turks in the mid-seventeenth century were no obstacle to Napoleon in the late eighteenth. Where sieges occurred, the attackers were usually able to defeat the defences within a matter of days or weeks, rather than weeks or months as previously. This era of rapidly moving armies continued through the 19th century, reaching its peak in the Franco-Prussian War. For example, the great Swedish white-elephant fortress of Karlsborg was built in the tradition of Vauban and intended as a reserve capital for Sweden, but it was obsolete before it was completed in 1869.

Modern warfare

siege at PetersburgEnlarge

siege at Petersburg

(18441845) in the American Civil War]]

Mainly as a result of the increasing firepower (such as machine guns) available to defensive forces, First World War trench warfare briefly revived a form of siege warfare. Although siege warfare had moved out from an urban setting because city walls had become ineffective against modern weapons, trench warfare was nonetheless able to utilize many of the techniques of siege warfare in its prosecution (sapping, mining, barrage and, of course, attrition) but on a much larger scale and on a greatly extended front. The development of the armoured tank at the end of World War I swung the pendulum back in favour of maneuver.

The Blitzkrieg of the Second World War truly showed that fixed fortifications are easily defeated by maneuver instead of frontal assault or long sieges. Battles that would have taken weeks of siege could now be avoided with the careful application of air power (such as the German paratrooper capture of Fort Eban, Belgium, early in World War II). The most important sieges of the Second World War were on the Eastern Front where bloody urban warfare marked the battles of Leningrad and Stalingrad. In these battles, the ruins of an urban landscape proved to be just as effective an obstacle to an advancing army as any fortifications.

During the Vietnam War the battles of Dien Bien Phu (1954) and Khe Sanh (1968) possessed siege-like characteristics. In both cases, the Vietcong were able to cut off the opposing army by capturing the surrounding rugged terrain. At Dien Bien Phu, the French were unable to use air power to overcome the siege and were defeated. But at Khe Sanh a mere 14 years later, advances in air power allowed the United States to overcome the siege and win the battle.

Police actions

Despite the overwhelming might of the modern state, siege tactics continue to be employed in police conflicts. This has been due to a number of factors, primarily risk to life, whether that of the police, the besieged, bystanders or hostages. Police make use of trained negotiators, psychologists and, if necessary, force, generally being able to rely on the support of their nation's armed forces if required. Unlike traditional military sieges, police sieges tend to last for hours or days rather than weeks, months or years.

See also

References

  1. May, Timothy. "Mongol Arms." Explorations in Empire, Pre-Modern Imperialism Tutorial: the Mongols. University of Wisconsin-Madison. 27 June 2004.

Further reading

External links