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 common, as proximity and fluctuating advantage can encourage diplomacy.
Failing a military outcome, sieges can often be decided by starvation, thirst, or disease, which can afflict either the attacker or defender. This form of siege, though, can take many months or even years, depending upon the size of the stores of food the fortified position holds. The attacking force can circumvallate the besieged place, which is to build a line of earth-works, consisting of a rampart and trench, surrounding it. During the process of circumvallation, the attacking force can be set upon by another force, an ally of the besieged place, due to the lengthy amount of time required to force it to capitulate. A defensive ring of forts outside the ring of circumvallated forts, called contravallation, is also sometimes used to defend the attackers from outside. Ancient cities in the Middle East show archaeological evidence of fortified city walls.
During the Warring States era of ancient China, there is both textual and archaeological evidence of prolonged sieges and siege machinery used against the defenders of city walls. Siege machinery was also a tradition of the ancient Greco-Roman world. 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. Medieval campaigns were generally designed around a succession of sieges. In the Napoleonic era, increasing use of ever more powerful cannons reduced the value of fortifications. In the 20th century, the significance of the classical siege declined. With the advent of mobile warfare, a single fortified stronghold is no longer as decisive as it once was. While traditional 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. Modern sieges are more commonly the result of smaller hostage, militant, or extreme resisting arrest situations.
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| Picture of the siege of Rancagua during the Chilean War of Independence |
Ancient period
The necessity of city walls
The Assyrians deployed large labour forces to build new palaces, temples, and defensive walls. Some settlements in the Indus Valley civilization were also fortified. By about 3500 BC, hundreds of small farming villages dotted the Indus River floodplain. Many of these settlements had fortifications and planned streets. The stone and mud brick houses of Kot Diji were clustered behind massive stone flood dikes and defensive walls, for neighbouring communities quarrelled constantly about the control of prime agricultural land. Mundigak (c. 2500 BC) in present-day south-east Afghanistan has defensive walls and square bastions of sun-dried bricks. City walls and fortifications were essential for the defence of the first cities in the ancient Near East. The walls were built of mudbricks, stone, wood, or a combination of these materials, depending on local availability. They may also have served the dual purpose of showing potential enemies the might of the kingdom. The great walls surrounding the Sumerian city of Uruk gained a widespread reputation. The walls were 9.5 km in length, and up to 12 m in height.
Later, the walls of Babylon, reinforced by towers, moats, and ditches, gained a similar reputation. In Anatolia, the Hittites built massive stone walls around their cities atop hillsides, taking advantage of the terrain. In Shang Dynasty China, at the site of Ao, large walls were erected in the 15th century BC that had dimensions of 20 m in width at the base and enclosed an area of some 1,900 m squared. The ancient Chinese capital for the State of Zhao, Handan, founded in 386 BC, also had walls that were 20 m wide at the base; they were 15 m tall, with two separate sides of its rectangular enclosure at a length of 1,400 m.
The cities of the Indus Valley Civilization showed less effort in constructing defences, as did the Minoan civilization on Crete. These civilizations probably relied more on the defence of their outer borders or sea shores. Unlike the ancient Minoan civilization, the Mycenaean Greeks emphasized the need for fortifications alongside natural defences of mountainous terrain, such as the massive Cyclopean walls built at Mycenae and other adjacent Late Bronze Age (c. 1600-1100 BC) centers of central and southern Greece.
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| Assyrians using siege ladders in a relief of attack on an enemy town during the reign of Tiglath-Pileser III 720-738 BCE from his palace at Kalhu (Nimrud) |
Archaeological evidence
Although there are depictions of sieges from the ancient Near East in historical sources and in art, there are very few examples of siege systems that have been found archaeologically. Of the few examples, several are noteworthy :
- The late 9th-century BC siege system surrounding Tell es-Safi/Gath, Israel, consists of a 2.5 km long siege trench, towers, and other elements, and is the earliest evidence of a circumvallation system known in the world. It was apparently built by Hazael of Aram Damascus, as part of his siege and conquest of Philistine Gath in the late 9th century BC (mentioned in II Kings 12:18).
- The late 8th-century BC siege system surrounding the site of Lachish (Tell el-Duweir) in Israel, built by Sennacherib of Assyria in 701 BC, is not only evident in the archaeological remains, but is described in Assyrian and biblical sources and in the reliefs of Sennacherib's palace in Nineveh.
- The siege of Alt-Paphos, Cyprus by the Persian army in the 4th century BC.
Depictions
The earliest representations of siege warfare have been dated to the Protodynastic Period of Egypt, c. 3000 BC. These show the symbolic destruction of city walls by divine animals using hoes.
The first siege equipment is known from Egyptian tomb reliefs of the 24th century BC, showing Egyptian soldiers storming Canaanite town walls on wheeled siege ladders. Later Egyptian temple reliefs of the 13th century BC portray the violent siege of Dapur, a Syrian city, with soldiers climbing scale ladders supported by archers.
Assyrian palace reliefs of the 9th to 7th centuries BC display sieges of several Near Eastern cities. Though a simple battering ram had come into use in the previous millennium, the Assyrians improved siege warfare and used huge wooden tower-shaped battering rams with archers positioned on top.
In ancient China, sieges of city walls (along with naval battles) were portrayed on bronze 'hu' vessels, like those found in Chengdu, Sichuan in 1965, which have been dated to the Warring States period (5th to 3rd centuries BC).
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| The Egyptian siege of Dapur in the 13th century BC, from Ramesseum, Thebes |
Tactics
Offensive
An attacker's first act in a siege might be a surprise attack, attempting to overwhelm the defenders before they were ready or were even aware there was a threat. This was how William de Forz captured Fotheringhay Castle in 1221.
The most common practice of siege warfare was to lay siege and just wait for the surrender of the enemies inside or, quite commonly, to coerce someone inside to betray the fortification. During the medieval period, negotiations would frequently take place during the early part of the siege. An attacker - aware of a prolonged siege's great cost in time, money, and lives - might offer generous terms to a defender who surrendered quickly. The defending troops would be allowed to march away unharmed, often retaining their weapons. However, a garrison commander who was thought to have surrendered too quickly might face execution by his own side for treason.
As a siege progressed, the surrounding army would build earthworks (a line of circumvallation) to completely encircle their target, preventing food, water, and other 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.
The Hittite siege of a rebellious Anatolian vassal in the 14th century BC ended when the queen mother came out of the city and begged for mercy on behalf of her people. The Hittite campaign against the kingdom of Mitanni in the 14th century BC bypassed the fortified city of Carchemish. If the main objective of a campaign was not the conquest of a particular city, it could simply be passed by. When the main objective of the campaign had been fulfilled, the Hittite army returned to Carchemish and the city fell after an eight-day siege.
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| Depiction of various siege machines in the mid-16th century |
Disease was another effective siege weapon, although the attackers were often as vulnerable as the defenders. In some instances, catapults or similar weapons were used to fling diseased animals over city walls in an early example of biological warfare. If all else failed, a besieger could claim the booty of his conquest undamaged, and retain his men and equipment intact, for the price of a well-placed bribe to a disgruntled gatekeeper. The Assyrian siege of Jerusalem in the 8th century BC came to an end when the Israelites bought them off with gifts and tribute, according to the Assyrian account, or when the Assyrian camp was struck by mass death, according to the Biblical account. Due to logistics, long-lasting sieges involving a minor force could seldom be maintained. A besieging army, encamped in possibly squalid field conditions and dependent on the countryside and its own supply lines for food, could very well be threatened with the disease and starvation intended for the besieged.
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 was developed for use by besieging armies. Ladders could be used to escalade over the defenses. Battering rams and siege hooks could also be used to force through gates or walls, while catapults, ballistae, trebuchets, mangonels, and onagers could be used to launch projectiles to break down a city's fortifications and kill its defenders. A siege tower, a substantial structure built to equal or greater height than the fortification's walls, could allow 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 mining. The defenders could dig counter-tunnels to cut into the attackers' works and collapse them prematurely.
Fire was often used as a weapon when dealing with wooden fortifications. The Byzantine Empire used Greek fire, which contained additives that made it hard to extinguish. Combined with a primitive flamethrower, it proved an effective offensive and defensive weapon.
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| Medieval trebuchets could sling about two projectiles per hour at enemy positions. |
Defensive
The universal method for defending against siege is the use of fortifications, principally walls and ditches, to supplement natural features. A sufficient supply of food and water was also important to defeat the simplest method of siege warfare: starvation. On occasion, the defenders would drive 'surplus' civilians out to reduce the demands on stored food and water.
During the Warring States period in China (481-221 BC), warfare lost its honorable, gentlemen's duty that was found in the previous era of the Spring and Autumn period, and became more practical, competitive, cut-throat, and efficient for gaining victory. The Chinese invention of the hand-held, trigger-mechanism crossbow during this period revolutionized warfare, giving greater emphasis to infantry and cavalry and less to traditional chariot warfare.
The philosophically pacifist Mohists (followers of the philosopher Mozi) of the 5th century BC believed in aiding the defensive warfare of smaller Chinese states against the hostile offensive warfare of larger domineering states. The Mohists were renowned in the smaller states (and the enemies of the larger states) for the inventions of siege machinery to scale or destroy walls. These included traction trebuchet catapults, eight-foot-high ballistas, a wheeled siege ramp with grappling hooks known as the Cloud Bridge (the protractible, folded ramp slinging forward by means of a counterweight with rope and pulley), and wheeled 'hook-carts' used to latch large iron hooks onto the tops of walls to pull them down.
When enemies attempted to dig tunnels under walls for mining or entry into the city, the defenders used large bellows (the type the Chinese commonly used in heating up a blast furnace for smelting cast iron) to pump smoke into the tunnels in order to suffocate the intruders.
Advances in the prosecution of sieges in ancient and medieval times naturally encouraged the development of a variety of defensive countermeasures. 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 machicolations and murder-holes, as well the preparation of hot or incendiary substances. Arrowslits (also called arrow loops or loopholes), sally ports (airlock-like 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 a 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 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 mortars and howitzers (in modern times), the traditional methods of defense became less effective against a determined siege.
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| 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. |
Siege accounts
Although there are numerous ancient accounts of cities being sacked, few contain any clues to how this was achieved. Some popular tales existed on how the cunning heroes succeeded in their sieges. The best-known is the Trojan Horse of the Trojan War, and a similar story tells how the Canaanite city of Joppa was conquered by the Egyptians in the 15th century BC. The Biblical Book of Joshua contains the story of the miraculous Battle of Jericho.
A more detailed historical account from the 8th century BC, called the Piankhi stela, records how the Nubians laid siege to and conquered several Egyptian cities by using battering rams, archers, and slingers and building causeways across moats.
Classical antiquity
During the Peloponnesian War, one hundred sieges were attempted and fifty-eight ended with the surrender of the besieged area.
Alexander the Great's army successfully besieged many powerful cities during his conquests. Two of his most impressive achievements in siegecraft took place in the siege of Tyre and the siege of the Sogdian Rock. His engineers built a causeway that was originally 60 m wide and reached the range of his torsion-powered artillery, while his soldiers pushed siege towers housing stone throwers and light catapults to bombard the city walls.
Most conquerors before him had found Tyre, a Phoenician island-city about 1 km from the mainland, impregnable. The Macedonians built a mole, a raised spit of earth across the water, by piling stones up on a natural land bridge that extended underwater to the island, and although the Tyrians rallied by sending a fire ship to destroy the towers, and captured the mole in a swarming frenzy, the city eventually fell to the Macedonians after a seven-month siege. In complete contrast to Tyre, Sogdian Rock was captured by stealthy attack. Alexander used commando-like tactics to scale the cliffs and capture the high ground, and the demoralized defenders surrendered.
The importance of siege warfare in the ancient period should not be underestimated. One of the contributing causes of Hannibal's inability to defeat Rome was his lack of siege engines, thus, while he was able to defeat Roman armies in the field, he was unable to capture Rome itself. The legionary armies of the Roman Republic and Empire are noted as being particularly skilled and determined in siege warfare. An astonishing number and variety of sieges, for example, formed the core of Julius Caesar's mid-1st-century BC conquest of Gaul (modern France).
In his Commentarii de Bello Gallico (Commentaries on the Gallic War), Caesar describes how, at the Battle of Alesia, the Roman legions created two huge fortified walls around the city. The inner circumvallation, 16 km, held in Vercingetorix's forces, while the outer contravallation kept relief from reaching them. The Romans held the ground in between the two walls. The besieged Gauls, facing starvation, eventually surrendered after their relief force met defeat against Caesar's auxiliary cavalry.
The Sicarii Zealots who defended Masada in AD 73 were defeated by the Roman legions, who built a ramp 100 m high up to the fortress's west wall.
During the Roman-Persian Wars, siege warfare was extensively being used by both sides.
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| Roman siege machines |
Medieval period
Arabia during Muhammad's era
The early Muslims, led by the Islamic prophet Muhammad, made extensive use of sieges during military campaigns. The first use was during the Invasion of Banu Qaynuqa. According to Islamic tradition, the invasion of Banu Qaynuqa occurred in 624 AD. The Banu Qaynuqa were a Jewish tribe expelled by Muhammad for allegedly breaking the treaty known as the Constitution of Medina by pinning the clothes of a Muslim woman, which led to her being stripped naked. A Muslim killed a Jew in retaliation, and the Jews in turn killed the Muslim man. This escalated to a chain of revenge killings, and enmity grew between Muslims and the Banu Qaynuqa, leading to the siege of their fortress. The tribe eventually surrendered to Muhammad, who initially wanted to kill the members of Banu Qaynuqa but ultimately yielded to Abdullah ibn Ubayy's insistence and agreed to expel the Qaynuqa.
The second siege was during the Invasion of Banu Nadir. According to The Sealed Nectar, the siege did not last long; the Banu Nadir Jews willingly offered to comply with the Muhammad's order and leave Madinah. Their caravan counted 600 loaded camels, including their chiefs, Huyai bin Akhtab, and Salam bin Abi Al-Huqaiq, who left for Khaibar, whereas another party shifted to Syria. Two of them embraced Islam, Yameen bin ‘Amr and Abu Sa‘d bin Wahab, and so they retained their personal wealth. Muhammad seized their weapons, land, houses, and wealth. Amongst the other booty he managed to capture, there were 50 armours, 50 helmets, and 340 swords. This booty was exclusively Muhammad's because no fighting was involved in capturing it. He divided the booty at his own discretion among the early Emigrants and two poor Helpers, Abu Dujana and Suhail bin Haneef.
Other examples include the Invasion of Banu Qurayza in February-March 627 and the siege of Ta'if in January 630.
Mongols and Chinese
In the Middle Ages, the Mongol Empire's campaign against China (then comprising the Western Xia Dynasty, Jin Dynasty, and Southern Song dynasty) by Genghis Khan until Kublai Khan, who eventually established the Yuan Dynasty in 1271, was very effective, allowing the Mongols 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 principal 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, Hulagu 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.
Another Mongol tactic was to use catapults to launch corpses of plague victims into besieged cities. The disease-carrying fleas from the bodies 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. In 1346, the bodies of Mongol warriors of the Golden Horde who had died of plague were thrown over the walls of the Crimean city of Kaffa (now Feodosiya) during the siege of Caffa. It has been speculated that this operation may have been responsible for the advent of the Black Death in Europe. The Black Death is estimated to have killed 30%-60% of Europe's population.
On the first night while laying siege to 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.
However, the Chinese were not completely defenseless, and from AD 1234 until 1279, the Southern Song Chinese held out against the enormous barrage of Mongol attacks. Much of this success in defense lay in the world's first use of gunpowder (i.e. with early flamethrowers, grenades, firearms, cannons, and land mines) to fight back against the Khitans, the Tanguts, the Jurchens, and then the Mongols.
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| Chinese and Korean troops assault the Japanese forces of Hideyoshi in the siege of Ulsan Castle during the Imjin War (1592-1598). |
The Chinese of the Song period also discovered the explosive potential of packing hollowed cannonball shells with gunpowder. Written later around 1350 in the Huo Long Jing, this manuscript of Jiao Yu recorded an earlier Song-era cast-iron cannon known as the 'flying-cloud thunderclap eruptor'. The manuscript stated that (Wade-Giles spelling) :
- The shells (phao) are made of cast iron, as large as a bowl and shaped like a ball. Inside they contain half a pound of 'magic' gunpowder (shen huo). They are sent flying towards the enemy camp from an eruptor (mu phao); and when they get there a sound like a thunder-clap is heard, and flashes of light appear. If ten of these shells are fired successfully into the enemy camp, the whole place will be set ablaze...
During the Ming Dynasty (AD 1368-1644), the Chinese were very concerned with city planning in regards to gunpowder warfare. The site for constructing the walls and the thickness of the walls in Beijing's Forbidden City were favoured by the Chinese Yongle Emperor (r. 1402-1424) because they were in pristine position to resist cannon volley and were built thick enough to withstand attacks from cannon fire.
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