Editing Defensive wall (section)

===Gunpowder era===
====Chinese city walls====
[[File:Defensive Wall of Prince Qin Mansion 03 2016-01.jpg|thumb|Remains of a defensive wall of Prince Qin Mansion, a citadel within [[Xi'an]]]]
[[File:Nanjing ShitouCheng.jpg|thumb|The Stone City is a wall in [[Nanjing]] dated to the [[Six Dynasties]] (220～589). Almost all of the original city is gone, but portions of the city wall remain. Not to be confused with the [[City Wall of Nanjing]].]]

{{main|Chinese city wall}}

While gunpowder and cannons were invented in China, China never developed wall breaking artillery to the same extent as other parts of the world. Part of the reason is probably because Chinese walls were already highly resistant to artillery and discouraged increasing the size of cannons.{{sfn|Andrade|2016|p=96}} In the mid-twentieth century a European expert in fortification commented on their immensity: "in China ... the principal towns are surrounded to the present day by walls so substantial, lofty, and formidable that the medieval fortifications of Europe are puny in comparison."{{sfn|Andrade|2016|p=96}} Chinese walls were thick. The eastern wall of [[Ancient Linzi]], established in 859 BC, had a maximum thickness of 43 metres and an average thickness of 20–30 metres.<ref>{{Cite book|url=https://books.google.com/books?id=sP-PN2StH2cC&q=linzi+43+metres&pg=PA214|title = The Formation of Chinese Civilization: An Archaeological Perspective|isbn = 0300093829|last1 = Chang|first1 = Kwang-Chih|last2 = Xu|first2 = Pingfang|last3 = Lu|first3 = Liancheng|last4 = Pingfang|first4 = Xu|last5 = Wangping|first5 = Shao|last6 = Zhongpei|first6 = Zhang|last7 = Renxiang|first7 = Wang|date = January 2005| publisher=Yale University Press }}</ref> Ming prefectural and provincial capital walls were {{convert|10|to|20|m}} thick at the base and {{convert|5|to|10|m}} at the top.

In Europe the height of wall construction was reached under the [[Roman Empire]], whose walls often reached {{convert|10|m}} in height, the same as many Chinese city walls, but were only {{convert|1.5|to|2.5|m}} thick. Rome's Servian Walls reached {{convert|3.6|and|4|m}} in thickness and {{convert|6|to|10|m}} in height. Other fortifications also reached these specifications across the empire, but all these paled in comparison to contemporary Chinese walls, which could reach a thickness of {{convert|20|m}} at the base in extreme cases. Even the walls of Constantinople which have been described as "the most famous and complicated system of defence in the civilized world,"{{sfn|Andrade|2016|p=92}} could not match up to a major Chinese city wall.{{sfn|Andrade|2016|p=97}} Had both the outer and inner walls of Constantinople been combined they would have only reached roughly a bit more than a third the width of a major wall in China.{{sfn|Andrade|2016|p=97}} According to [[Philo]] the width of a wall had to be {{convert|4.5|m}} thick to be able to withstand ancient (non-gunpowder) siege engines.{{sfn|Purton|2009|p=363}} European walls of the 1200s and 1300s could reach the Roman equivalents but rarely exceeded them in length, width, and height, remaining around {{convert|2|m}} thick. When referring to a very thick wall in medieval Europe, what is usually meant is a wall of {{convert|2.5|m}} in width, which would have been considered thin in a Chinese context.{{sfn|Andrade|2016|p=98}} There are some exceptions such as the [[Hillfort of Otzenhausen]], a Celtic ringfort with a thickness of {{convert|40|m}} in some parts, but Celtic fort-building practices died out in the early medieval period.{{sfn|Andrade|2016|p=339}} Andrade goes on to note that the walls of the ''marketplace'' of Chang'an were thicker than the walls of major European capitals.{{sfn|Andrade|2016|p=98}}

Aside from their immense size, Chinese walls were also structurally different from the ones built in medieval Europe. Whereas European walls were mostly constructed of stone interspersed with gravel or rubble filling and bonded by limestone mortar, Chinese walls had tamped earthen cores which absorbed the energy of artillery shots.{{sfn|Andrade|2016|p=99}} Walls were constructed using wooden frameworks which were filled with layers of earth tamped down to a highly compact state, and once that was completed the frameworks were removed for use in the next wall section. Starting from the Song dynasty these walls were improved with an outer layer of bricks or stone to prevent erosion, and during the Ming, earthworks were interspersed with stone and rubble.{{sfn|Andrade|2016|p=99}} Most Chinese walls were also sloped rather than vertical to better deflect projectile energy.{{sfn|Andrade|2016|p=100}}

{{blockquote|The defensive response to cannon in Europe was to build relatively low and thick walls of packed earth, which could both withstand the force of cannon balls and support their own, defensive cannon. Chinese wall-building practice was, by happenstance, extremely resistant to all forms of battering. This held true into the twentieth century, when even modern explosive shells had some difficulty in breaking through tamped earth walls.{{sfn|Lorge|2008|p=43}}|Peter Lorge}}

The Chinese Wall Theory essentially rests on a cost benefit hypothesis, where the Ming recognized the highly resistant nature of their walls to structural damage, and could not imagine any affordable development of the guns available to them at the time to be capable of breaching said walls. Even as late as the 1490s a Florentine diplomat considered the French claim that "their artillery is capable of creating a breach in a wall of eight feet in thickness"{{sfn|Andrade|2016|p=101}} to be ridiculous and the French "braggarts by nature".{{sfn|Andrade|2016|p=101}} Very rarely did cannons blast breaches in city walls in Chinese warfare. This may have been partly due to cultural tradition. Famous military commanders such as [[Sun Tzu]] and [[Zheng Zhilong]] recommended not to directly attack cities and storm their walls. Even when direct assaults were made with cannons, it was usually by focusing on the gates rather than the walls. There were instances where cannons were used against walled fortifications, such as by [[Koxinga]], but only in the case of small villages. During Koxinga's career, there is only one recorded case of capturing a settlement by bombarding its walls: the siege of Taizhou in 1658. In 1662, the Dutch found that bombarding the walls of a town in [[Fujian Province]] had no effect and they focused on the gates instead just as in Chinese warfare. In 1841, a 74-gun British warship bombarded a Chinese coastal fort near Guangzhou and found that it was "almost impervious to the efforts of horizontal fire."{{sfn|Reger|2016|p=162-164}} In fact ''twentieth'' century explosive shells had some difficulty creating a breach in tamped earthen walls.{{sfn|Lorge|2008|p=43}}

{{blockquote|We fought our way to Nanking and joined in the attack on the enemy capital in December. It was our unit which stormed the Chunghua Gate. We attacked continuously for about a week, battering the brick and earth walls with artillery, but they never collapsed. The night of December 11, men in my unit breached the wall. The morning came with most of our unit still behind us, but we were beyond the wall. Behind the gate great heaps of sandbags were piled up. We 'cleared them away, removed the lock, and opened the gates, with a great creaking noise. We'd done it! We'd opened the fortress! All the enemy ran away, so we didn't take any fire. The residents too were gone. When we passed beyond the fortress wall we thought ''we'' had occupied this city.{{sfn|Cook|2000|p=32}}|Nohara Teishin, on the Japanese capture of [[Nanjing]] in 1937}}

====Bastions and star forts====
{{main|Bastion|Bastion fort}}

[[File:Palmanova1600.jpg|right|thumb|17th-century map of the city of [[Palmanova]], [[Italy]], an example of a [[Republic of Venice|Venetian]] star fort]]
[[File:Shouyuquanshu 1638.jpg|thumb|Chinese angled bastion fort, 1638]]
As a response to gunpowder artillery, European fortifications began displaying architectural principles such as lower and thicker walls in the mid-1400s.{{sfn|Andrade|2016|p=211}} Cannon towers were built with artillery rooms where cannons could discharge fire from slits in the walls. However, this proved problematic as the slow rate of fire, reverberating concussions, and noxious fumes produced greatly hindered defenders. Gun towers also limited the size and number of cannon placements because the rooms could only be built so big. Notable surviving artillery towers include a seven layer defensive structure built in 1480 at [[Fougères]] in [[Brittany]], and a four layer tower built in 1479 at Querfurth in Saxony.{{sfn|Arnold|2001|p=37}}

The star fort, also known as the bastion fort, ''trace italienne'', or renaissance fortress, was a style of fortification that became popular in Europe during the 16th century. The bastion and star fort was developed in Italy, where the Florentine engineer [[Giuliano da Sangallo]] (1445–1516) compiled a comprehensive defensive plan using the geometric [[bastion]] and full ''trace italienne'' that became widespread in Europe.{{sfn|Nolan|2006|p=67}}

The main distinguishing features of the star fort were its angle bastions, each placed to support their neighbor with lethal crossfire, covering all angles, making them extremely difficult to engage with and attack. Angle bastions consisted of two faces and two flanks. Artillery positions positioned at the flanks could fire parallel into the opposite bastion's line of fire, thus providing two lines of cover fire against an armed assault on the wall, and preventing mining parties from finding refuge. Meanwhile, artillery positioned on the bastion platform could fire frontally from the two faces, also providing overlapping fire with the opposite bastion.{{sfn|Arnold|2001|p=40}} Overlapping mutually supporting defensive fire was the greatest advantage enjoyed by the star fort. As a result, sieges lasted longer and became more difficult affairs. By the 1530s the bastion fort had become the dominant defensive structure in Italy.{{sfn|Arnold|2001|p=45}}

Outside Europe, the star fort became an "engine of European expansion,"{{sfn|Andrade|2016|p=211}} and acted as a force multiplier so that small European garrisons could hold out against numerically superior forces. Wherever star forts were erected the natives experienced great difficulty in uprooting European invaders.{{sfn|Andrade|2016|p=211}}

In China, [[Sun Yuanhua]] advocated for the construction of angled [[bastion forts]] in his ''Xifashenji'' so that their cannons could better support each other. The officials Han Yun and Han Lin noted that cannons on square forts could not support each side as well as bastion forts. Their efforts to construct bastion forts, and their results, were limited. Ma Weicheng built two bastion forts in his home county, which helped fend off a [[Qing dynasty|Qing]] incursion in 1638. By 1641, there were ten bastion forts in the county. Before bastion forts could spread any further, the Ming dynasty fell in 1644, and they were largely forgotten as the Qing dynasty was on the offensive most of the time and had no use for them.{{sfn|Andrade|2016|p=214}}