Siege
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A siege is a military blockade of a city or fortress with the intent of conquering by attrition or assault. The term derives from sedere, Latin for to sit.[1] Generally speaking, 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.
A siege occurs when an attacker encounters a city or fortress that cannot be easily taken by a coup de main and refuses to surrender. Sieges involve surrounding the target and blocking the reinforcement or escape of troops or provision of supplies (a tactic known as investment[2]), typically coupled with attempts to reduce the fortifications by means of siege engines, artillery bombardment, mining (also known as sapping), or the use of deception or treachery to bypass defences. Failing a military outcome, sieges can often be decided by starvation, thirst or disease, which can afflict either the attacker or defender.
Sieges probably predate the development of cities as large population centres. Ancient cities in the Middle East show archaeological evidence of having had 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 cannon 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 such as the Waco Siege.
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[edit] Ancient era
[edit] The necessity of city walls
The Assyrians deployed large labour forces to build new palaces, temples and defensive walls.[3] 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 quarreled constantly about the control of prime agricultural land.[4] Mundigak (c. 2500 BC) in present-day southeast Afghanistan has defensive walls and square bastions of sun-dried bricks.[3]
City walls and fortifications were essential for the defense of the first cities in the ancient Near East. The walls were built of mud bricks, stone, wood or a combination of these materials depending on local availability. They may also have served the dual purpose of showing presumptive 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 (5.9 mi) in length, and up to 12 m (39 ft) in height.
Later the walls of Babylon, reinforced by towers and moats, gained a similar reputation. In Anatolia, the Hittites built massive stone walls around their cities, taking advantage of the hillsides. In Shang Dynasty China, at the site of Ao, large walls were erected in the 15th century BC that had dimensions of 20 m (66 ft) in width at the base and enclosed an area of some 2,100 yards (1,900 m) squared.[5] The ancient Chinese capital for the State of Zhao, Handan, founded in 386 BC, also had walls that were 20 m (66 ft) wide at the base; they were 15 m (49 ft) tall, with two separate sides of its rectangular enclosure at a length of 1,530 yd (1,400 m).[5]
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 defenses of mountainous terrain, such as the massive Cyclopean walls built at Mycenae during the last half of the 2nd millennium BC.[citation needed]
[edit] 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.
[edit] 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 century BC to 3rd century BC).[6]
[edit] Tactics
[edit] Offensive
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 a siege a 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 Egyptian siege of Megiddo in the 15th century BC lasted for 7 months before its inhabitants surrendered. 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.
The well-known 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.
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 defences. 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 in order 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.[7]
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 gate-keeper.
[edit] 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.[8]
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.[9] 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 protractable, 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.[10]
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.[9]
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 machicolations and murder-holes, as well the preparation of hot or incendiary substances.[11] Arrow slits (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 defences, whether natural or augmented, were also vital to defenders.[12]
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.[citation needed]
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) mortars and howitzers, the traditional methods of defence became less effective against a determined siege.[13]
[edit] 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.
[edit] Greco-Roman era
Alexander the Great's Macedonian army successfully besieged many powerful cities during his astounding 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 (200 ft) 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 a siege train, 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, 10 miles (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.
[edit] Chinese and Mongols
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, with their armies was extremely 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, Hulegu used twenty catapults against the Bab al-Iraq (Gate of Iraq) alone.[14] 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.[citation needed]
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 besieged Crimean city of Kaffa (now Feodosiya). It has been speculated that this operation may have been responsible for the advent of the Black Death in Europe.[15] The Black Death is estimated to have killed 30% – 60% of Europe's population.[16]
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.[17]
However, the Chinese were not completely defenceless, 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.
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' (fei yun pi-li pao). 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...[18]
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 favored 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.[citation needed]
For more see Technology of the Song Dynasty.
[edit] Age of gunpowder
The introduction of gunpowder and the use of cannons brought about a new age in siege warfare. Cannons were first used in Song Dynasty China during the early 13th century, but 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. They could also fire projectiles in a straight line, so that they could destroy the bases of high walls. 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, the capital of the Byzantine Empire, were broken through in just six weeks by the 62 cannons 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 the European wars.
Once siege guns were developed the techniques for assaulting a town or a fortress became well known and ritualized. The attacking army would surround a town. Then the town would be asked to surrender. If they did not comply the besieging army would surround the town with temporary fortifications to stop sallies from the stronghold or relief getting in. The attackers would then build a length of trenches parallel to the defences and just out of range of the defending artillery. They would then dig a trench towards the town in a zigzag pattern so that it could not be enfiladed by defending fire. Once within artillery range another parallel trench would be dug with gun emplacements. This was called sapping.
If necessary using the first artillery fire for cover this process would be repeated until guns were close enough to be laid accurately to make a breach in the fortifications. In order to allow the forlorn hope and support troops to get close enough to exploit the breach, more zigzag trenches could be dug even closer to the walls with more parallel trenches to protect and conceal the attacking troops. After each step in the process the besiegers would ask the besieged to surrender. If the forlorn hope stormed the breach successfully the defenders could expect no mercy.
[edit] Emerging theories
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.
[edit] New fortresses
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 backed, in front and behind, with earth. Towers were reformed into triangular bastions.[19] This design matured into the trace italienne. Star-shaped fortresses surrounding towns and even cities with outlying defences proved very difficult to capture, even for a well equipped army.[20] 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). During World War II trace italienne fortresses could still present a formidable challenge, for example in the last days of World War II, during the Battle in Berlin that saw some of the heaviest urban fighting of the war, the Soviets did not attempt to storm the Spandau Citadel (built between 1559 and 1594) but chose to invest it and negotiate its surrender.[21]
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 Italian Wars. 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. The densely populated areas of Northern Italy and the United Provinces (the Netherlands) were infamous for their high degree of fortification of cities. It made campaigns in these areas very hard to successfully conduct, considering even minor cities had to be captured by siege within the span of the campaigning season. In the Dutch case, the possibility of flooding large parts of the land provided an additional obstacle to besiegers, for example at the Siege of Leiden. 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.
[edit] Marshal Vauban and Van Coehoorn
At the end of the 17th century, two influential military engineers, the French Marshal Vauban and the Dutch military engineer Menno van Coehoorn, 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. Both engineers developed their ideas independently but came to similar general rules regarding defensive construction and offensive action against fortifications. Both were skilled in conducting sieges and defences themselves. Before Vauban and Van Coehoorn, sieges had been somewhat slapdash operations. Vauban and Van Coehoorn refined besieging to a science with a methodical process that, if uninterrupted, would break even the strongest fortifications. Examples of their styles of fortifications are Arras (Vauban) and the no-longer existent fortress of Bergen op Zoom (Van Coehoorn). The main differences between the two lay in the difference in terrain on which Vauban and Van Coehoorn constructed their defences: Vauban in the sometimes more hilly and mountainous terrain of France, Van Coehoorn in the flat and floodable lowlands of the Netherlands.
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 contravallation, 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 circumvallation 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 a