Defensive wall

• 1. Introduction

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  A defensive wall is a fortification meant to protect a city, town, or settlement from people who might attack it. Picture the proto-city of Jericho in the West Bank, ringed by a wall as early as the 8th millennium BC. Picture Uruk in ancient Sumer, one of the oldest walled cities the world has ever recorded. For thousands of years, from those first earthen banks to slabs of steel and concrete bristling with barbed wire, walls have been a near necessity for nearly every city. They could be simple palisades thrown up around a hillfort. They could be the immense, mortar-bound stone of an empire. Why did so many societies, separated by oceans and millennia, arrive at the same answer? Why did some walls survive into the modern age while others were torn down deliberately? And how did a wall come to mean far more than safety, standing instead for the pride and independence of the people inside it? The story runs from rammed earth in ancient China to a concrete barrier across a divided city, and it turns on a single question that engineers kept answering in different ways: how thick, how tall, and how do you keep an enemy out.

• 2. Earth, Brick, And Stone

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  The earliest known town wall in Europe belonged to Solnitsata, built in the 6th or 5th millennium BC. Existing ancient walls are almost always masonry, though builders also worked in brick and timber depending on what they had. The land itself often did part of the job. Where a river or a coastline ran near a settlement, the wall could be tied into that terrain to make it harder to approach. In mountainous country, walls called letzis were paired with castles to seal off whole valleys from attack. Some fortifications grew far beyond a single city. The Great Wall of China, the Walls of Benin, Hadrian's Wall, the Anastasian Wall, and the Atlantic Wall all stretched past city limits to enclose regions or mark out territory. By contrast, the rougher banks of earth or stone heaped around hillforts, ringworks, and early castles tend to be called ramparts rather than walls. Simpler did not always mean weaker, and the choice of material followed the landscape as much as the threat. In the Indus Valley, that landscape was a floodplain, which shaped fortifications of a very particular kind.

• 3. Walls Across The World

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  By about 3500 BC, hundreds of small farming villages dotted the Indus floodplain, many with fortifications and planned streets. At Kot Diji, stone and mud brick houses clustered behind massive stone flood dykes and defensive walls, because neighboring communities quarreled constantly over prime farmland. Mundigak, around 2500 BC in present-day south-east Afghanistan, raised defensive walls and square bastions of sun dried brick. In Mesopotamia the labor was state-scaled. The Assyrians put large workforces to building palaces, temples, and defensive walls, and Babylon grew famous partly through the building program of Nebuchadnezzar, who expanded its walls and built the Ishtar Gate. The Persians sealed their frontiers with the Derbent Wall and the Great Wall of Gorgan, set on either side of the Caspian Sea against nomadic nations. Southeast Asia took a different path, where the idea of a town fully enclosed by walls did not fully develop until Europeans arrived. Burma was the exception, with walled towns by 1566, and Rangoon in 1755 stood behind teak stockades on an earthen rampart with six gates, each flanked by brick towers. Elsewhere the walls came fast in the 16th and 17th centuries against European naval attack. Ayutthaya built its walls in 1550, Banten, Jepara, Tuban, and Surabaya had theirs by 1600, and Makassar by 1634. In Korea, fortresses called eupseongs served both military and administrative roles from the time of Silla until the end of the Joseon dynasty, when in 1910 the occupying power ordered most of them demolished.

• 4. The Chinese Wall

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  The eastern wall of ancient Linzi, established in 859 BC, reached a maximum thickness of 43 metres and averaged 20 to 30 metres. That scale defined Chinese fortification. Large rammed earth walls went up from the Shang dynasty, around 1600 to 1050 BC, and the capital at ancient Ao carried enormous walls of this kind. Stone arrived during the Warring States, 481 to 221 BC, but mass conversion to stone did not begin in earnest until the Tang dynasty, 618 to 907 AD. Ming prefectural and provincial capital walls ran 10 to 20 metres thick at the base and 5 to 10 metres at the top. The structure mattered as much as the size. Chinese walls had tamped earthen cores that absorbed the energy of artillery shots, built inside wooden frameworks filled with earth pounded to a highly compact state. From the Song dynasty onward an outer layer of brick or stone guarded against erosion, and Ming builders mixed in stone and rubble. Most walls were sloped rather than vertical, the better to deflect a projectile. According to Tonio Andrade, this immense thickness held back the development of larger cannon, since even industrial-era artillery struggled to breach it. He notes that the walls around the marketplace of Chang'an were thicker than the walls of major European capitals. The contrast with Europe ran deep, and it would shape how an entire continent answered the arrival of gunpowder.

• 5. The European Answer

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  In ancient Greece, the great stone walls of Mycenaean sites like Mycenae used blocks so huge they were called cyclopean. Athens in the classical era ran a long set of parallel stone walls, the Long Walls, down to its guarded seaport at Piraeus. Yet neither ancient Sparta nor ancient Rome bothered with walls for a long time, trusting their armies instead. Rome changed its mind. The Romans wrapped their cities in massive, mortar-bound stone, leaving the largely surviving Aurelian Walls of Rome and the Theodosian Walls of Constantinople, along with gates like the Porta Nigra in Trier or Newport Arch in Lincoln. The numbers reveal the difference from China. Roman walls often reached 10 metres in height, matching many Chinese walls, but stood only 1.5 to 2.5 metres thick. Rome's Servian Walls hit 3.6 to 4 metres in thickness and 6 to 10 metres in height. The philosopher Philo held that a wall needed 4.5 metres of thickness to withstand ancient siege engines. European walls of the 1200s and 1300s rarely exceeded the Roman figures, hovering near 2 metres, and a wall called very thick in medieval Europe usually meant 2.5 metres, which a Chinese builder would have judged thin. The Celts complicate the picture. In Central Europe they raised large fortified settlements the Romans called oppida, and the Hillfort of Otzenhausen, a Celtic ringfort, reached 40 metres thick in places before such fort-building died out in the early medieval period.

• 6. Gunpowder And The Star Fort

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  Even as late as the 1490s, a Florentine diplomat dismissed the French boast that their artillery could breach a wall eight feet thick, calling the French braggarts by nature. The skepticism was earned, because in China cannon rarely blasted breaches in city walls at all. Famous commanders like Sun Tzu and Zheng Zhilong advised against storming walls directly. When attackers did bring cannon, they aimed at the gates. Koxinga captured a settlement by bombarding its walls only once on record, at the siege of Taizhou in 1658. In 1662 the Dutch found that shelling a town's walls in Fujian Province did nothing, so they turned on the gates. In 1841 a 74-gun British warship hammered a Chinese coastal fort near Guangzhou and found it almost impervious to horizontal fire. Europe answered gunpowder differently. From the mid-1400s its fortifications turned lower and thicker, with cannon towers whose artillery rooms fired through slits, though the slow rate of fire, the concussions, and the fumes badly hampered defenders. The breakthrough was the star fort, also called the bastion fort or trace italienne, popular across Europe in the 16th century. The Florentine engineer Giuliano da Sangallo, who lived from 1445 to 1516, compiled a full defensive plan around the geometric bastion. Its angle bastions, each with two faces and two flanks, supported their neighbors with lethal crossfire that covered every angle and denied refuge to mining parties. Outside Europe the star fort became an engine of European expansion, letting small garrisons hold out against far larger forces. In China, Sun Yuanhua argued for angled bastion forts in his Xifashenji, and Ma Weicheng built two in his home county that helped fend off a Qing incursion in 1638. By 1641 the county held ten, but the Ming dynasty fell in 1644, and the bastion fort was largely forgotten.

• 7. Why The Walls Came Down

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  Today a vanished city wall often shows only as a ditch, a ring road, or a park, and sometimes a street name carrying a word like wall or glacis is the last clue it ever existed. Several forces brought the walls down. As cities grew, defensive strategy shifted toward forts ringing the city rather than a single enclosure. Gunpowder made walls less effective, since siege cannon could blast through and let armies march in. In the 19th century, less value was placed on the architectural or historical worth of fortifications, and many were demolished to modernize the cities. The losses were uneven. Some complete fortifications were restored, as at Carcassonne. Several medieval town walls survived intact, including the walls of Tallinn, the town walls of York and Canterbury in England, and Ávila and Tossa del Mar in Spain, with Lugo keeping an intact Roman wall. In Germany, a monument preservation law under the Bavarian King Ludwig I of Bavaria led to the near-complete preservation of Rothenburg ob der Tauber, Nördlingen, Berching, and Dinkelsbühl, and saved the countless small fortified towns of the Franconia region. The archaeologist Giulia Bellato captures why walls were such frequent targets in medieval warfare. She notes that walls were the visible marker that defined a city as such and helped define its inhabitants as citizens. That symbolic weight outlived the walls themselves, and it returned in a strikingly different form in the modern age.

• 8. Walls Of The Modern Age

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  Berlin's city wall, standing from the 1730s to the 1860s and partly made of wood, existed mainly to let the city impose tolls on goods, and secondly to keep soldiers of the garrison from deserting. The modern wall could serve almost any purpose except surviving a siege. The Berlin Wall, built around West Berlin by the German Democratic Republic from 1961 to 1989, was raised to stop citizens from fleeing to the West German exclave, complete with a double wall and an interstitial zone of fire that is now rare. Other barriers divide nations and communities. The Korean Demilitarized Zone splits North and South Korea near the 38th parallel north, the Nicosia Wall along the Green Line divides North and South Cyprus, and the peace lines run through Belfast in Northern Ireland. The Gaza-Israel barrier, first built by Israel in 1971 and rebuilt and upgraded since, has been effective in stopping attackers from crossing into Israel from Gaza. In September 2014, Ukraine announced a European Rampart along its border with Russia to support an application for visa-free movement with the European Union. The materials changed with the purpose. Most modern walls are steel and concrete, vertical plates fitted with the least possible space between them and rooted firmly in the ground, their tops often jutting out and strung with barbed wire, built in straight lines and watched from towers at the corners. The same logic now wraps private life and diplomacy alike, in gated communities where guards control access, and in embassy districts like the Legation Quarter that stood in Beijing in the late 19th and early 20th centuries.