Asiege (Latin:sedere,lit. 'to sit')^[1] is amilitaryblockade of a city, orfortress, with the intent of conquering by attrition, or by well-prepared assault.Siege warfare (also calledsiegecrafts orpoliorcetics) is a form of constant, low-intensity conflict characterized by one party holding a strong, static, defensive position. Consequently, an opportunity fornegotiation between combatants is common, as proximity and fluctuating advantage can encouragediplomacy.

A siege occurs when an attacker encounters a city or fortress that cannot be easily taken by a quick assault, and which refuses tosurrender. Sieges involve surrounding the target to block provision of supplies and reinforcement or escape of troops (a tactic known as "investment").^[2] This is typically coupled with attempts to reduce the fortifications by means ofsiege engines,artillery bombardment,mining (also known as sapping), or the use of deception or treachery to bypass defenses.

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 arampart 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 showarchaeological evidence of fortifiedcity walls. During theWarring States period ofancient China, there is both textual and archaeological evidence of prolonged sieges and siege machinery used against thedefenders of city walls. Siege machinery was also a tradition of the ancientGreco-Roman world. During theRenaissance and theearly modern period, siege warfare dominated the conduct of war in Europe.Leonardo da Vinci gained some of his renown from design of fortifications.Medieval campaigns were generally designed around a succession of sieges. In theNapoleonic era, increasing use of ever more powerfulcannons reduced the value of fortifications. In the 20th century, the significance of the classical siege declined. With the advent ofmobile 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 extremeresisting arrest situations.

TheAssyrians deployed large labour forces to build new palaces, temples, and defensive walls.^[3] Some settlements in theIndus Valley civilization were also fortified. By about 3500 BC, hundreds of small farming villages dotted theIndus River floodplain. Many of these settlements had fortifications and planned streets.

The stone and mud brick houses ofKot Diji were clustered behind massive stone flood dikes and defensive walls, for neighbouring communities quarrelled constantly about the control of prime agricultural land.^[4]Mundigak (c. 2500 BC) in present-day south-eastAfghanistan has defensive walls and square bastions ofsun-dried bricks.^[3]

City walls and fortifications were essential for the defence of the first cities in theancient 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 theSumerian city ofUruk 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 ofBabylon, reinforced by towers, moats, and ditches, gained a similar reputation. InAnatolia, theHittites built massive stone walls around their cities atop hillsides, taking advantage of the terrain. InShang 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 1,900 m (2,100 yd) squared.^[5] The ancient Chinese capital for theState 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 1,400 m (1,530 yd).^[5]

The cities of the Indus Valley Civilization showed less effort in constructing defences, as did theMinoan civilization onCrete. These civilizations probably relied more on the defence of their outer borders or sea shores. Unlike the ancient Minoan civilization, theMycenaean Greeks emphasized the need for fortifications alongside natural defences of mountainous terrain, such as the massiveCyclopean walls built atMycenae and other adjacent Late Bronze Age (c. 1600–1100 BC) centers of central and southern Greece.^[6]

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 surroundingTell es-Safi/Gath,Israel, consists of a 2.5 km (1.6 mi) long siege trench, towers, and other elements, and is the earliest evidence of acircumvallation system known in the world. It was apparently built byHazael ofAram Damascus, as part of his siege and conquest ofPhilistine Gath in the late 9th century BC (mentioned inII Kings 12:18).
• The late 8th-century BC siege system surrounding the site ofLachish (Tell el-Duweir) in Israel, built bySennacherib ofAssyria in 701 BC, is not only evident in the archaeological remains, but is described in Assyrian andbiblical sources and in the reliefs of Sennacherib's palace inNineveh.
• The siege of Alt-Paphos,Cyprus by thePersian army in the 4th century BC.

The earliest representations of siege warfare have been dated to theProtodynastic 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 stormingCanaanite town walls on wheeled siege ladders. Later Egyptian temple reliefs of the 13th century BC portray the violentsiege 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 onbronze'hu' vessels, like those found inChengdu,Sichuan in 1965, which have been dated to theWarring States period (5th to 3rd centuries BC).^[7]

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 howWilliam de Forz capturedFotheringhay Castle in 1221.^[8]

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.^[8]

As a siege progressed, the surrounding army would buildearthworks (a line ofcircumvallation) 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 eveneach other.

TheHittite 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 ofMitanni in the 14th century BC bypassed the fortified city ofCarchemish. 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.

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 ofbiological 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-placedbribe to a disgruntled gatekeeper. TheAssyrian siege of Jerusalem in the 8th century BC came to an end when theIsraelites bought them off with gifts and tribute, according to theAssyrian account, or when the Assyrian camp was struck by mass death, according to theBiblical 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 ofsiege engines was developed for use by besieging armies. Ladders could be used toescalade over the defenses.Battering rams andsiege hooks could also be used to force through gates or walls, whilecatapults,ballistae,trebuchets,mangonels, andonagers could be used to launch projectiles to break down a city's fortifications and kill its defenders. Asiege 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 thefoundations of the walls, and then deliberately collapsing or exploding the tunnel. This process is known asmining. 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. TheRoman Empire usedGreek fire, which contained additives that made it hard to extinguish. Combined with a primitiveflamethrower, it proved an effective offensive and defensive weapon.^[9] A sallying out might also occur with such weapons, or if the siege was of a location on a coastline, from ships launched from the harbor of the location.

The universal method for defending against siege is the use of fortifications, principally walls andditches, 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.^[10]

During theWarring States period in China (481–221 BC), warfare lost its honorable, gentlemen's duty that was found in the previous era of theSpring and Autumn period, and became more practical, competitive, cut-throat, and efficient for gaining victory.^[11] The Chinese invention of the hand-held, trigger-mechanismcrossbow during this period revolutionized warfare, giving greater emphasis to infantry and cavalry and less to traditionalchariot warfare.

The philosophicallypacifistMohists (followers of the philosopherMozi) 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 trebuchetcatapults, 8-foot (2.4 m) highballistas, a wheeled siege ramp withgrappling 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.^[12]

When enemies attempted to dig tunnels under walls for mining or entry into the city, the defenders used largebellows (the type the Chinese commonly used in heating up ablast furnace for smeltingcast iron) to pump smoke into the tunnels in order to suffocate the intruders.^[11]

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 theconcentric castle from the period of theCrusades—and more dangerous to attackers—witness the increasing use ofmachicolations andmurder-holes, as well the preparation ofhot or incendiary substances.^[13]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 bydrawbridges,portcullises, andbarbicans.Moats and other water defenses, whether natural or augmented, were also vital to defenders.^[14]

In the EuropeanMiddle Ages, virtually all large cities had city walls—Dubrovnik inDalmatia is a well-preserved example—and more important cities hadcitadels,forts, orcastles. 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 likeTábor inBohemia, similar to those used much later inVietnam during theVietnam War.^{[citation needed]}

Until the invention ofgunpowder-based weapons (and the resulting higher-velocity projectiles), the balance of power and logistics definitely favored the defender. With the invention of gunpowder, cannon andmortars andhowitzers (in modern times), the traditional methods of defense became less effective against a determined siege.^[15]

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 theTrojan Horse of theTrojan War, and a similar story tells how theCanaanite city ofJoppa was conquered by the Egyptians in the 15th century BC. The BiblicalBook of Joshua contains the story of the miraculousBattle of Jericho.

A more detailed historical account from the 8th century BC, called thePiankhi stela, records how theNubians laid siege to and conquered several Egyptian cities by using battering rams, archers, and slingers and buildingcauseways across moats.

During thePeloponnesian War, one hundred sieges were attempted and fifty-eight ended with the surrender of the besieged area.^[16]

Alexander the Great's army successfully besieged many powerful cities during his conquests. Two of his most impressive achievements in siegecraft took place in thesiege of Tyre and thesiege of the Sogdian Rock. Hisengineers built acauseway that was originally 60 m (200 ft) wide and reached the range of his torsion-powered artillery, while his soldiers pushedsiege towers housing stone throwers and light catapults to bombard the city walls.

Most conquerors before him had foundTyre, aPhoenician island-city about 1 km (1,100 yd) from the mainland, impregnable. The Macedonians built amole, a raised spit of earth across the water, by piling stones up on a naturalland bridge that extended underwater to the island, and although the Tyrians rallied by sending afire 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 thedemoralized defenders surrendered.

The importance of siege warfare in the ancient period should not be underestimated. One of the contributing causes ofHannibal's inability to defeat Rome was his lack ofsiege engines, thus, while he was able to defeat Roman armies in the field, he was unable to capture Rome itself. The legionary armies of theRoman Republic andEmpire are noted as being particularly skilled and determined in siege warfare. An astonishing number and variety of sieges, for example, formed the core ofJulius Caesar's mid-1st-century BC conquest ofGaul (modern France).

In hisCommentarii de Bello Gallico (Commentaries on the Gallic War), Caesar describes how, at theBattle of Alesia, theRoman legions created two huge fortified walls around the city. The inner circumvallation, 16 km (10 mi), held inVercingetorix's forces, while the outercontravallation 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.

TheSicariiZealots who defendedMasada in AD 73 were defeated by the Roman legions, who built a ramp 100 metres (330 ft) high up to the fortress's west wall.

During theRoman–Persian Wars, siege warfare was extensively being used by both sides.

In the Middle Ages, theMongol Empire's campaign against China (then comprising theWestern Xia dynasty,Jin dynasty, andSouthern Song dynasty) byGenghis Khan untilKublai Khan, who eventually established theYuan 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 ofAleppo,Hulagu used twenty catapults against theBab al-Iraq (Gate of Iraq) alone.^[17]

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 ofplague victims into besieged cities. The disease-carryingfleas from the bodies would then infest the city, and the plague would spread, allowing the city to be easily captured, although thistransmission mechanism was not known at the time. In 1346, the bodies of Mongol warriors of theGolden Horde who had died of plague were thrown over the walls of theCrimean city of Kaffa (nowFeodosiya) during thesiege of Caffa. It has been speculated that this operation may have been responsible for the advent of theBlack Death in Europe.^[18] The Black Death is estimated to have killed 30%–60% of Europe's population.^[19]

On the first night while laying siege to a city, the leader of the Mongol forces would lead from a whitetent: 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.^[20]

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 earlyflamethrowers,grenades,firearms, cannons, andland mines) to fight back against theKhitans, theTanguts, theJurchens, and then the Mongols.

The Chinese of the Song period also discovered the explosive potential of packing hollowed cannonball shells with gunpowder. Written laterc. 1350 in theHuo Long Jing, this manuscript ofJiao 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...^[21]

During theMing 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'sForbidden City were favoured by the ChineseYongle 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.^[22]

For more, seeTechnology of the Song dynasty.

The introduction of gunpowder and the use ofcannons brought about a new age in siege warfare. Cannons were first used inSong dynasty China during the early 13th century, but did not become significant weapons for another 150 years or so. In early decades, cannons could do little against strong castles and fortresses, providing little more than smoke and fire. By the 16th century, however, 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, farther, 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, theTheodosian Walls ofConstantinople, the capital of theRoman Empire, were broken through injust six weeks by the 62 cannons ofMehmed II's army, although in the end the conquest was a long and extremely difficult siege with heavy Ottoman casualties due to the repeated attempts at taking the city by assault.

However, new fortifications, designed to withstand gunpowder weapons, were soon constructed throughout Europe. During theRenaissance and theearly 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 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 stopsallies from the stronghold or relief getting in. The attackers would next build a length of trenches parallel to the defenses (these are known as the "first parallel") and just out of range of the defending artillery. They would dig a trench (known as a forward) towards the town in azigzag pattern so that it could not beenfiladed by defending fire. Once they were within artillery range, they would dig another parallel (the "second parallel") trench and fortify it with gun emplacements. This technique is commonly called entrenchment.

If necessary, using the first artillery fire for cover, the forces conducting the siege would repeat the process until they placed their guns close enough to be laid (aimed) accurately to make a breach in the fortifications. In order to allow theforlorn 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.

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 ofFerdinand and Isabella was able to conquerMoorish strongholds inGranada in 1482–1492 that had held out for centuries before the invention of cannons.

In the early 15th century, Italian architectLeon Battista Alberti wrote a treatise entitledDe 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 1494–1495 that the new fortifications were built on a large scale.Charles VIII invaded Italy with an army of 18,000 men and a horse-drawnsiege-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.

The most effective way to protect walls against cannon fire proved to be depth (increasing the width of the defenses) 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.^[23] This design matured into thetrace italienne.Star-shaped fortresses surrounding towns and even cities with outlying defenses proved very difficult to capture, even for a well-equipped army.^[24] 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 theBattle in Berlin, that saw some of the heaviest urban fighting of the war, the Soviets did not attempt to storm theSpandau Citadel (built between 1559 and 1594), but chose toinvest it and negotiate its surrender.^[25]

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 asSiena, 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 theItalian 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 ofNorthern Italy and theUnited 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 thesiege 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.

At the end of the 17th century, two influential military engineers, the FrenchMarshalVauban and the Dutch military engineerMenno van Coehoorn, developed modern fortification to its pinnacle, refining siege warfare without fundamentally altering it: ditches would be dug; walls would be protected byglacis; andbastions wouldenfilade 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 defenses 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 areArras (Vauban) and the no-longer-existent fortress ofBergen op Zoom (Van Coehoorn). The main differences between the two lay in the difference in terrain on which Vauban and Van Coehoorn constructed their defenses: 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 bothsorties 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 ofcontravallation, 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 about 600 metres (2,000 ft) 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 metres (1,000 ft). This line contained smaller guns. The final line would be constructed only 30 to 60 metres (100 to 200 ft) from the fortress. This line would contain themortars and would act as astaging area for attack parties once the walls were breached. Van Coehoorn developed a small and easily movable mortar named thecoehorn, variations of which were used in sieges until the 19th century. It would also be from this line that miners 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 assaps) needed to be sharply jagged.

Another element of a fortress was thecitadel. Usually, a citadel was a "mini fortress" within the larger fortress, sometimes designed as areduit, 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, especiallytyphus, 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 ofstrategy for the besieging army was whether or not to allow the encamped city to surrender. Usually, it was preferable to graciously allow asurrender, 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. Moreover, if an attacking army had a reputation of killing and pillaging regardless of a surrender, then other cities' defensive efforts would be redoubled. Usually, a city would surrender (with no honour lost) when its inner lines of defense were reached by the attacker. In case of refusal, however, the inner lines would have to be stormed by the attacker and the attacking troops would be seen to be justified in sacking the city.

Siege warfare dominated in Western Europe for most of the 17th and 18th centuries. An entire campaign, or longer, could be used in a single siege (for example,Ostend in 1601–1604;La Rochelle in 1627–1628). This resulted in extremely prolonged 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 relieving armies, but the principle was a slow, grinding victory by the greater economic power. The relatively rare attempts at forcingpitched battles (Gustavus Adolphus in 1630; the French against the Dutch in 1672 or 1688) were almost always expensive failures.

The exception to this rule were the English.^[26] During theEnglish Civil War, anything which tended to prolong the struggle, or seemed like want of energy and avoidance of a decision, was bitterly resented by the men of both sides. In France and Germany, the prolongation of a war meant continued employment for the soldiers, but in England, both sides were looking to end the war quickly. Even when in the end theNew Model Army—a regular professional army—developed the original decision-compelling spirit permeated the whole organisation, as was seen when pitched against regular professional continental troops theBattle of the Dunes during theInterregnum.^[27]

Experienced commanders on both sides in the English Civil War recommended the abandonment of garrisoned fortifications for two primary reasons. The first, as for example proposed by the RoyalistSir Richard Willis to King Charles, was that by abandoning the garrisoning of all but the most strategic locations in one's own territory, far more troops would be available for the field armies, and it was the field armies which would decide the conflict. The other argument was that by slighting potential strong points in one's own territory, an enemy expeditionary force, or local enemy rising, would find it more difficult to consolidate territorial gains against an inevitable counterattack. SirJohn Meldrum put forward just such an argument to the ParliamentaryCommittee of Both Kingdoms, to justify his slighting ofGainsborough in Lincolnshire.^[28][29]

Sixty years later, during theWar of the Spanish Succession, theDuke of Marlborough preferred to engage the enemy in pitched battles, rather than engage in siege warfare, although he was very proficient in both types of warfare.

On 15 April 1746, the day before theBattle of Culloden, atDunrobin Castle, a party ofWilliam Sutherland's militia conducted the last siege fought on the mainland of Great Britain against Jacobite members ofClan MacLeod.

In theFrench Revolutionary andNapoleonic Wars, new techniques stressed the division of armies into all-arms corps that would march separately and only come together on the battlefield. The less-concentrated army could now live off the country and move more rapidly over a larger number of roads.

Fortresses commanding lines of communication could be bypassed and would no longer stop an invasion. Since armies could not live off the land indefinitely,Napoleon Bonaparte always sought a quick end to any conflict by pitched battle. This military revolution was described and codified byClausewitz.

Advances in artillery made previously impregnable defenses useless. For example, the walls ofVienna that had held off theTurks in the mid-17th century were no obstacle toNapoleon in the early 19th.

Where sieges occurred (such as thesiege of Delhi and thesiege of Cawnpore during theIndian Rebellion of 1857), the attackers were usually able to defeat the defenses within a matter of days or weeks, rather than weeks or months as previously. The great Swedish white-elephant fortress ofKarlsborg 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.

Railways, when they were introduced, made possible the movement and supply of larger armies than those that fought in the Napoleonic Wars. It also reintroduced siege warfare, as armies seeking to use railway lines in enemy territory were forced to capture fortresses which blocked these lines.

During theFranco-Prussian War, the battlefield front lines moved rapidly through France. However, the Prussian and other German armies were delayed for months at thesiege of Metz and thesiege of Paris, due to the greatly increased firepower of the defending infantry, and the principle of detached or semi-detached forts with heavy-caliberartillery. This resulted in the later construction of fortress works across Europe, such as the massive fortifications atVerdun. It also led to the introduction of tactics which sought to induce surrender by bombarding the civilian population within a fortress, rather than the defending works themselves.

Thesiege of Sevastopol during theCrimean War and thesiege of Petersburg (1864–1865) during theAmerican Civil War showed that modern citadels, when improved by improvised defences, could still resist an enemy for many months. Thesiege of Plevna during theRusso-Turkish War (1877–1878) proved that hastily constructed field defenses could resist attacks prepared without proper resources, and were a portent of the trench warfare of World War I.

Advances in firearms technology without the necessary advances in battlefield communications gradually led to the defense again gaining the ascendancy. An example of siege during this time, prolonged during 337 days due to the isolation of the surrounded troops, was thesiege of Baler, in which a reduced group of Spanish soldiers was besieged in a small church by thePhilippine rebels in the course of thePhilippine Revolution and theSpanish–American War, until months after theTreaty of Paris, the end of the conflict.

Furthermore, the development ofsteamships availed greater speed toblockade runners, ships with the purpose of bringing cargo, e.g. food, to cities under blockade, as withCharleston, South Carolina, during the American Civil War.

Mainly as a result of the increasing firepower (such asmachine guns) available to defensive forces,First World Wartrench 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 use 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.

More traditional sieges of fortifications took place in addition to trench sieges. Thesiege of Tsingtao was one of the first major sieges of the war, but the inability for significant resupply of the German garrison made it a relatively one-sided battle. The Germans and the crew of an Austro-Hungarianprotected cruiser put up a hopeless defense and, after holding out for more than a week, surrendered to the Japanese, forcing the GermanEast Asia Squadron to steam towards South America for a new coal source.^{[dubious –discuss]}

The other major siege outside Europe during the First World War was inMesopotamia, at thesiege of Kut. After a failed attempt to move on Baghdad, stopped by the Ottomans at the bloodyBattle of Ctesiphon, the British and their large contingent of Indiansepoy soldiers were forced to retreat to Kut, where the Ottomans under German GeneralBaron Colmar von der Goltz laid siege. The British attempts to resupply the force via theTigris river failed, and rationing was complicated by the refusal of many Indian troops to eat cattle products. By the time the garrison fell on 29 April 1916, starvation was rampant. Conditions did not improve greatly under Turkish imprisonment. Along with the battles ofTanga,Sandfontein,Gallipoli, andNamacurra, it would be one of Britain's numerous embarrassing colonial defeats of the war.

The largest sieges of the war, however, took place in Europe. The initial German advance into Belgium produced four major sieges: theBattle of Liège, thesiege of Namur, thesiege of Maubeuge, and thesiege of Antwerp. All four would prove crushing German victories, at Liège and Namur against the Belgians, at Maubeuge against the French and at Antwerp against a combined Anglo-Belgian force. The weapon that made these victories possible were the GermanBig Berthas and theSkoda 305 mm Model 1911 siege mortars, one of the best siege mortars of the war,^[30] on loan from Austria-Hungary. These huge guns were the decisive weapon of siege warfare in the 20th century, taking part at Przemyśl, the Belgian sieges, on the Italian Front and Serbian Front, and even being reused in World War II.

At thesiege of Przemyśl, during World War I, theAustro-Hungarian garrison showed excellent knowledge of siege warfare, not only waiting for relief, but sending sorties into Russian lines and employing an active defense that resulted in the capture of the Russian GeneralLavr Kornilov. Despite its excellent performance, the garrison's food supply had been requisitioned for earlier offensives, a relief expedition was stalled by the weather, ethnic rivalries flared up between the defending soldiers, and a breakout attempt failed. When the commander of the garrison Hermann Kusmanek finally surrendered, his troops were eating their horses and the first attempt of large-scale air supply had failed. It was one of the few great victories obtained by either side during the war; 110,000 Austro-Hungarian prisoners were marched back to Russia. Use of aircraft for siege running, bringing supplies to areas under siege, would nevertheless prove useful in many sieges to come.

The largest siege of the war, and arguably the roughest, most gruesome battle in history, was theBattle of Verdun. Whether the battle can be considered true siege warfare is debatable. Under the theories ofErich von Falkenhayn, it is more distinguishable as purely attrition with a coincidental presence of fortifications on the battlefield. When considering the plans ofCrown Prince Wilhelm, purely concerned with taking the citadel and not with French casualty figures, it can be considered a true siege. The main fortifications wereFort Douaumont,Fort Vaux, and the fortified city of Verdun itself. The Germans, through the use of huge artillery bombardments, flamethrowers, and infiltration tactics, were able to capture both Vaux and Douaumont, but were never able to take the city, and eventually lost most of their gains. It was a battle that, despite the French ability to fend off the Germans, neither side won. The German losses were not worth the potential capture of the city, and the French casualties were not worth holding the symbol of her defense.

The development of the armoredtank and improvedinfantrytactics at the end of World War I swung the pendulum back in favor of maneuver, and with the advent of Blitzkrieg in 1939, the end of traditional siege warfare was at hand. TheMaginot Line would be the prime example of the failure of immobile, post–World War I fortifications. Although sieges would continue, it would be in a totally different style and on a reduced scale.

TheBlitzkrieg of the Second World War truly showed that fixed fortifications are easily defeated by manoeuvre instead of frontal assault or long sieges. The greatMaginot Line was bypassed, and battles that would have taken weeks of siege could now be avoided with the careful application of air power (such as the Germanparatrooper capture ofFort Eben-Emael, Belgium, early in World War II).

The most important siege was thesiege of Leningrad, which lasted over 29 months, about half of the duration of the entire Second World War. The siege of Leningrad resulted in the deaths of someone million of the city's inhabitants.^[31] Along with theBattle of Stalingrad, the siege of Leningrad on theEastern Front was the deadliest siege of a city in history. In the west, apart from theBattle of the Atlantic, the sieges were not on the same scale as those on the European Eastern front; however, there were several notable or critical sieges: the island ofMalta, for which the population won theGeorge Cross andTobruk. In theSouth-East Asian theatre, there was the siege ofSingapore, and in theBurma campaign, sieges ofMyitkyina, theAdmin Box,Imphal, andKohima, which was the high-water mark for the Japanese advance intoIndia.

Thesiege of Sevastopol saw the use of the heaviest and most powerful individual siege engines ever to be used: the German800 mm railway gun and the600 mm siege mortar. Though a single shell could have disastrous local effect, the guns were susceptible to air attack in addition to being slow to move.

Throughout the war both the Western Allies and the Germans tried to supply forces besieged behind enemy lines with ad-hocairbridges. Sometimes these attempts failed, as happened to the besiegedGerman Sixth Army theBattle of Stalingrad, and sometimes they succeeded as happened during theBattle of the Admin Box (5 – 23 February 1944) and the shortSiege of Bastogne (December 1944).

The logistics of strategic airbridge operations were developed by the Americans flyingmilitary transport aircraft fromIndia toChina overthe Hump (1942–1945), to resupply theChinese war effort ofChiang Kai-shek, and to the USAAFXX Bomber Command (duringOperation Matterhorn).^{[citation needed]}

Tactical airbridge methods were developed and, as planned, used extensively for supplying theChindits duringOperation Thursday (February – May 1944). The Chindits, a specially trained division of theBritish andIndian armies, were flown deep behind Japanese front lines in the South-East Asian theatre to jungle clearings in Burma where they set up fortified airheads from which they sailed out to attack Japanese lines of communications, while defending the bases from Japanese counterattacks. The bases were re-supplied by air with casualties flown out by returning aircraft. When the Japanese attacked in strength the Chindits abandoned the bases and either moved to new bases, or back to Allied lines.^[32]

Several times during theCold War the western powers had to use their airbridge expertise.

• TheBerlin Blockade from June 1948 to September 1949, the Western Powers flew over 200,000 flights, providing to West Berlin up to 8,893 tons of necessities each day.
• Airbridge was used extensively during theBattle of Dien Bien Phu during theFirst Indochina War, but failed to prevent its fall to theViệt Minh in 1954.
• Inthe next Vietnam War, airbridge proved crucial during the siege of the American base atKhe Sanh in 1968. The resupply it provided kept theNorth Vietnamese Army from capturing the base.

In both Vietnamese cases, theViet Minh andNLF were able to cut off the opposing army by capturing the surrounding rugged terrain.^[33] At Dien Bien Phu, the French were unable to use air power to overcome the siege and were defeated.^[34] However, at Khe Sanh, a mere 14 years later, advances in air power—and a reduction in Vietnamese anti-aircraft capability—allowed the United States to withstand the siege. The resistance of US forces was assisted by thePAVN andPLAF forces' decision to use the Khe Sanh siege as a strategic distraction to allow their mobile warfare offensive, the firstTet Offensive, to unfold securely.

The Battle of Khe Sanh displays typical features of modern sieges, as the defender has greater capacity to withstand the siege, the attacker's main aim is to bottle operational forces or create a strategic distraction, rather than take the siege to a conclusion.

In neighboring Cambodia, at that time known as theKhmer Republic, theKhmer Rouge used siege tactics to cut off supplies fromPhnom Penh to other government-held enclaves in an attempt to break the will of the government to continue fighting.

In 1972, during the Easter offensive, the siege ofAn Lộc Vietnam occurred. ARVN troops and U.S. advisers and air power successfully defeated communist forces. The Battle of An Lộc pitted some 6,350 ARVN men against a force three times that size. During the peak of the battle, ARVN had access to only one 105 mm howitzer to provide close support, while the enemy attack was backed by an entire artillery division. ARVN had no tanks, the NVA communist forces had two armoured regiments. ARVN prevailed after over two months of continuous fighting. As General Paul Vanuxem, a French veteran of the Indochina War, wrote in 1972 after visiting the liberated city of An Lộc: "An Lộc was the Verdun of Vietnam, where Vietnam received as in baptism the supreme consecration of her will."

During the1982 Lebanon War, theIsrael Defence ForcesbesiegedBeirut, the capital ofLebanon, to quickly realize their goals including the eviction of thePalestine Liberation Organization from the country.

During theYugoslav Wars in the 1990s,Republika Srpska forcesbesiegedSarajevo, the capital ofBosnia-Herzegovina. The siege lasted from 1992 until 1996.

Numerous sieges haven taken place during theSyrian civil war, such as thesiege of Homs,siege of Kobanî,siege of Deir ez-Zor (2014–2017),siege of Nubl and al-Zahraa, andsiege of al-Fu'ah and Kafriya.

Multiple sieges took place in the2022 Russian invasion of Ukraine, most notably thesiege of Mariupol.^[35]

TheGaza war contained multiple sieges, including thesiege of Gaza City and thesiege of Khan Yunis.

Siege tactics continue to be employed inpolice contexts; such a siege is typically called astandoff or, in law enforcementjargon, abarricade situation. Standoffs may result from crimes and incidents such asrobberies,raids,search andarrest warrants,prison riots, orterrorist attacks. Standoffs occur due to a variety of factors, most prominently the safety of police (against whom the besieged may have the upper hand), the besiegedsuspects (who police generally intend toarrest), bystanders (who may be in thecrossfire), andhostages (who may be injured or killed by the suspects).

The optimal result of most standoffs is a peaceful resolution: the safe extraction of hostages and bystanders, and the peaceful surrender and arrest of the hostage-takers. To ensure this, police make use of trainednegotiators andpsychologists to learn the hostage-takers' demands (and meet said demands if feasible or permissible), gain the hostage-takers' trust, clarify that police do not intend to kill them or will evenlet them go (regardless of whether such claims are true), and coax the hostage-takers into surrendering or at least releasing hostages. In the event a peaceful resolution is impossible—negotiations fail or do not proceed, hostages are released but the hostage-takers refuse to surrender, the hostage-takers resist violently, or hostages are killed—police may respond in force, generally being able to rely onpolice tactical units or evenmilitary support if possible and required.

Most standoffs are much shorter than military sieges, often lasting hours or days at most. Lengthy sieges may still occur, albeit rarely, such as the 51-day-long 1993Waco siege. Most standoffs end in a peaceful resolution (i.e.1973 Brooklyn hostage crisis,1997 Roby standoff), though some may end in a police or military assault (i.e. 1994Air France Flight 8969 hijacking, 1980Iranian Embassy siege) or, in the worst-case scenarios, the deaths of authorities, hostage-takers, or hostages (i.e. 1985MOVE bombing, 1985EgyptAir Flight 648 hijacking, 2004Beslan school siege, 2022Robb Elementary School shooting). The aforementioned worst-case scenarios often result from poor planning, tactics, or negotiations on the part of the authorities (e.g. accidental killings of hostages byUnit 777 during the EgyptAir Flight 648 hijacking), or from violent acts committed by the hostage-takers (e.g.suicide bombings and executions during the Beslan school siege).

In some jurisdictions, depending on certain circumstances, standoffs that would usually be handled by police may be transferred to the military. For example, in theUnited Kingdom, standoffs with terrorists may be transferred to military responsibility for a military assault on the besieged. The threat of such an action ended the 1975Balcombe Street siege, but the 1980Iranian Embassy siege ended in a military assault and the deaths of all but one of the hostage-takers.

• Battleplan (documentary TV series)
• Blitzkrieg
• Breastwork (fortification)
• Infiltration
• Last stand
• Maneuver warfare
• Medieval warfare

• Sangar (fortification)
• Siege engines
• Siege equipment
• Tunnel warfare

Lists

• List of established military terms
• List of sieges

• Alchon, Suzanne Austin (2003).A pest in the land: new world epidemics in a global perspective. University of New Mexico Press. p. 21.ISBN 0-8263-2871-7.
• Baldock, Thomas Stanford (1809).Cromwell as a Soldier. K. Paul, Trench, Trübner & Company. pp. 515–520.
• Beevor, Antony (2002).Berlin: The Downfall 1945. Viking-Penguin Books.ISBN 0-670-88695-5.
• Firth, C. H. (1902).Cromwell's Army: A History of the English Soldier During the Civil Wars, the Commonwealth and the Protectorate. Sussex: Methurn & Company. p. 29.
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• Funderburk, Jordan (2021).Siege Operations for 21st Century Warfare. U.S. Army.Archived from the original on 6 May 2022.
• Grousset, René (1970).The Empire of the Steppes: A History of Central Asia. Rutgers University Press. p. 362.ISBN 0-8135-1304-9.
• Hoskin, John; Howland, Carol (2006).Vietnam. New Holland Publishers. p. 105.ISBN 978-1-84537-551-5.^{[permanent dead link‍]}
• Stewart, William (1998).Dictionary of images and symbols in counselling (1st ed.). Jessica Kingsley. p. 105.ISBN 1-85302-351-5.
• Morocco, John (1984).Thunder from Above: Air War, 1941–1968. Boston: Boston Publishing Company.^{[ISBN missing]}
• Needham, Joseph (1986).Science and Civilization in China. Vol. 4. Taipei: Caves Books Ltd.^{[ISBN missing]}
• Needham, Joseph (1986).Science and Civilization in China. Vol. 5. Taiepi: Caves Books Ltd.^{[ISBN missing]}
• Needham, Joseph (1986).Science and Civilization in China. Vol. 5. Taipei: Caves Books Ltd.^{[ISBN missing]}
• Reynolds, Francis Joseph; Churchill, Allen Leon; Miller, Francis Trevelyan (1916).The story of the great war: history of the European War from official sources; complete historical records of events to date. P.F. Collier & Son. p. 406.
• Roland, Alex (1992). "Secrecy, Technology, and War: Greek Fire and the Defense of Byzantium, Technology and Culture".Technology and Culture.33 (4):655–679.doi:10.2307/3106585.JSTOR 3106585.S2CID 113017993.
• Sellman, R. R. (1954).Castles and Fortresses. Methuen.^{[ISBN missing]}
• Stearns, Peter N. (2001).The Encyclopedia of World History: ancient, medieval, and modern (6th ed.). Houghton Mifflin Books. p. 17.ISBN 0-395-65237-5.
• Symonds, Richard (1859). Long, Charles Edward (ed.).Diary of the Marches of the Royal Army During the Great Civil War. Works of the Camden Society. Vol. 74. The Camden Society. p. 270.
• Townshend, Charles (2000).The Oxford History of Modern War.Oxford University Press. pp. 211, 212.ISBN 0-19-285373-2.
• Turnbull, Stephen R. (2002).Siege Weapons of the Far East. Oxford: Osprey Publishing Ltd.^{[ISBN missing]}
• Wheelis, M. (2002)."Biological warfare at the 1346 siege of Caffa".Emerg Infect Dis.8 (9). Center for Disease Control:971–975.doi:10.3201/eid0809.010536.PMC 2732530.PMID 12194776.
• Windrow, Martin (2005).The Last Valley: Dien Bien Phu and the French defeat in Vietnam. London: Cassell.^{[ISBN missing]}

• Duffy, Christopher (1996) [1975].Fire & Stone: The Science of Fortress Warfare (1660–1860) (2nd ed.). New York: Stackpole Books.
• Duffy, Christopher (1996).Siege Warfare: Fortress in the Early Modern World, 1494–1660. Routledge and Kegan Paul.
• Duffy, Christopher (1985).Siege Warfare, Volume II: The Fortress in the Age of Vauban and Frederick the Great. London: Routledge and Kegan Paul.
• Garlan, Yvon (1974).Recherches de poliorcétique grecque (in French). Paris: De Boccard.
• Lynn, John A. (1999).The Wars of Louis XIV. Pearson.ISBN 0582056292.
• May, Timothy. (2004)."Mongol Arms".Explorations in Empire, Pre-Modern Imperialism Tutorial: the Mongols. University of Wisconsin-Madison. Archived fromthe original on 18 May 2008.
• Ostwald, Jamel (2007).Vauban Under Siege: Engineering Efficiency and Martial Vigor in the War of the Spanish Succession. History of Warfare. Vol. 41 (illustrated ed.). Brill.ISBN 978-90-04-15489-6.
• Warner, Philip (1968).Sieges of the Middle Ages. G. Bell & Sons.

Historiography

• Bachrach, Bernard S (1994). "Medieval siege warfare: a reconnaissance".Journal of Military History.58 (1):119–133.doi:10.2307/2944182.JSTOR 2944182.

• Secrets of Lost Empires: Medieval Siege (PBS) Informative and interactive webpages about medieval siege tactics.