Fortification

• 1. Introduction

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  A fortification is a military construction built to defend territory in war, and to hold rule over a region in peacetime. The word comes from the Latin fortis, meaning strong, and facere, meaning to make. Long before any of that vocabulary existed, the impulse may have begun with something far simpler. Archeologists describe its earliest root as primitive man blocking the entrances of his caves for security from large carnivores. From that crude gesture to steel and concrete, the same problem keeps returning. How do you keep a stronger or more numerous enemy on the outside? The answers stretch from mud-brick mounds in the Nile Valley to tunnel networks buried beneath the native rock. They run through the cyclopean stone walls of Mycenae, the trench Muhammad ordered dug around Medina, and a chain-reaction explosion on an airfield in South Vietnam. Why did the tallest walls eventually become a liability? Why would an engineer choose to sink a fort into a ditch rather than raise it toward the sky? And how did the arrival of a single technology, gunpowder, force the entire craft to start over?

• 2. Branches Of The Craft

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  Castrametation is the old name for the art of setting out a military camp or constructing a fortification, used since the time of the Roman legions. The discipline splits into two main branches. Permanent fortification is the heavy, lasting kind. Field fortification is the temporary kind thrown up for an immediate need. Between them sits an intermediate category called semipermanent fortification. A castle sits apart from the generic fort or fortress in one specific way. It is the residence of a monarch or noble, and it commands a particular defensive territory. The Indian treatise on military strategy, the Arthashastra, took the classification even further. It describes six major types of forts, each differentiated by its major mode of defense.

• 3. The First Walled Settlements

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  Amnya Fort in western Siberia has been described as one of the oldest known fortified settlements, and the northernmost Stone Age fort. The chronology of early walls is dense with competing firsts. Near the Bulgarian town of Provadia, a walled settlement now called Solnitsata dates from 4700 BC. It had a diameter of about 300 feet, housed 350 people in two-story houses, and was ringed by stone blocks 6 feet high and 4.5 feet thick. Yet even that is younger than the walled town of Sesklo in Greece, which dates from 6800 BC. Uruk in ancient Sumer is one of the world's oldest known walled cities. The Ancient Egyptians built fortresses on the frontiers of the Nile Valley and ringed their cities with circle-shaped mud-brick walls. Because so many ancient fortifications were built of mud brick, they survive today as little more than mounds of dirt. In Scotland, a massive prehistoric stone wall dated to 3200 BC surrounded the temple of Ness of Brodgar. Named the Great Wall of Brodgar, it stood 4 meters thick and 4 meters tall, and its function appears to have been symbolic or ritualistic. The Assyrians, by contrast, deployed large labor forces to raise palaces, temples, and defensive walls for plainly military ends.

• 4. Stone, Earth, And The Casemate

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  Sparta and ancient Rome went without walls for a long time, choosing to trust their militaries instead. The exception proves how varied early practice was. In Bronze Age Malta, the settlement of Borg in-Nadur preserves a bastion built around 1500 BC. At Heuneburg in Germany, around 600 BC, forts rose on a limestone foundation topped by a mud-brick wall about 4 meters tall, probably crowned by a roofed walkway that brought the total height to 6 meters. That wall was clad in lime plaster and regularly renewed, and towers protruded outward from it. The Celts built large fortified settlements called oppida. The Oppidum of Manching, near modern Ingolstadt in Bavaria, was founded in the 3rd century BC and lasted until roughly 50 to 30 BC. At its peak it covered 380 hectares, where 5,000 to 10,000 people lived inside walls 7.2 kilometers long. The casemate wall was a different idea entirely. It is a double wall with transverse walls dividing the gap into chambers, used in the archeology of Israel and the wider Near East. The earliest example, at Ti'inik, dates to the 16th century BC. During a siege those chambers could be packed with soil and rocks to stiffen the outer wall against battering rams. Casemate walls peaked in Iron Age II, then began giving way to sturdier solid walls by the 9th century BC, probably because the Neo-Assyrian Empire had developed more effective battering rams.

• 5. Walls Across The World

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  India uses the single word fort for all of its old fortifications, and the country now holds over 180 of them. The state of Maharashtra alone has more than 70, many built by Shivaji, founder of the Maratha Empire. The Indus Valley tells a story of constant local friction. By about 3500 BC hundreds of small farming villages dotted the Indus floodplain, and the stone and mud-brick houses of Kot Diji huddled behind massive flood dykes and defensive walls, because neighboring communities bickered constantly over prime agricultural land. Different sites chose different materials. Dholavira used stone walls, Harappa used baked bricks, and Kalibangan used mud brick with bastions. In China, large rammed-earth walls were built as far back as the Shang dynasty, roughly 1600 to 1050 BC. Mass conversion to stone did not begin in earnest until the Tang dynasty, between 618 and 907 AD. The Great Wall of China had been built since the Qin dynasty, though its present form is mostly a remodeling from the Ming dynasty. In Beijing, the walls of the Forbidden City were established in the early 15th century by the Yongle Emperor. Across the Roman world, the Aurelian Walls of Rome and the Theodosian Walls of Constantinople still stand in large part, and Hadrian's Wall was thrown across northern England in AD 122, following a visit by the emperor Hadrian.

• 6. Forts Beyond Europe

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  The Ivatan people of the Batanes islands built fortifications called idjang on hills and elevated ground, reached only by a rope ladder that could be drawn up when invaders arrived. Across the wider world, people who never met one another converged on similar solutions. The Igorots built stone-walled forts averaging several meters in width, around 2000 BC. The Muslim Filipinos of the south built strong fortresses called kota or moong, made of stone and bamboo and ringed by trench networks, which sheltered entire families rather than warriors alone. In Africa, the walls of Benin were ranked by the Guinness Book of Records in 1974 as the world's second longest man-made structure and the most extensive earthwork in the world. Yoruba fortifications often used a double wall of trenches and ramparts, and in the Congo forests, concealed ditches bristled with rows of sharpened stakes. The Ashanti built powerful log stockades, some over a hundred yards long, impervious to artillery fire. Many failed anyway, because Ashanti guns and gunpowder gave little sustained killing power, and British troops repeatedly overran the stockades with old-fashioned bayonet charges after laying down covering fire.

• 7. The Gunpowder Revolution

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  Cannons arrived on the 14th-century battlefield and made medieval-style fortifications largely obsolete. The fix was counterintuitive. Walls had to come down rather than go up. Builders sank them into ditches fronted by earth slopes that could absorb and disperse the energy of cannon fire. The transition is visible at Sarzanello in north-west Italy, built between 1492 and 1502, which carries both crenellated medieval walls and a ravelin-like angular gun platform. At Rhodes, the fortifications were frozen in 1522, leaving it the only European walled town that still shows the shift between medieval and modern styles. Giovanni Battista Zanchi published a manual on building fortifications in 1554. The new logic produced star-shaped forts layered with hornworks and bastions, of which Fort Bourtange is an excellent example. By the 18th century these enclosures could no longer be made large enough for the enormous field armies of Europe. So after refortifying the Prussian cities of Koblenz and Koln from 1815, engineers adopted the ring fortress. Detached forts were pushed several hundred meters out from the old enceinte, sited to support one another and to keep enemy artillery from reaching the town.

• 8. Going Underground And Becoming Obsolete

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  Explosive shells in the 19th century wrecked the star fort, ripping apart its bastions, flanking batteries, and carefully plotted lines of fire. The response drove the fort downward. Engineers developed the polygonal style, cutting a deep, vertically sided ditch directly into rock or soil and sweeping it with fire from blockhouses set inside it. The fort's profile dropped very low, its ditch protected by caponiers, its entrance a sunken gatehouse reached by a rolling bridge that could be withdrawn. Deep passages and tunnel networks linked the firing points to magazines and machine rooms buried far below. Steel-and-concrete fortifications were common through the 19th and early 20th centuries, but advances since World War I made large-scale fortifications obsolete in most situations. Permanent fortification had two fatal weaknesses. The first was that escalating artillery and airpower could destroy almost any target located, and by 1950 nuclear weapons could erase whole cities. The second was permanency itself, since with mobile warfare an attacker could simply go around. That was the fate of the Siegfried Line, the Stalin Line, and the Atlantic Wall. The Maginot Line was the exception, designed to force the Germans to invade through Belgium or Switzerland instead, and it succeeded in that aim. Field fortification rose to take over, favoring defense in depth, with the bulk of fighting power held back in mobile reserves rather than the line itself.

  On the morning of the 16th of May 1965, at Bien Hoa in South Vietnam, aircraft were being refueled and armed when a chain-reaction explosion destroyed 13 aircraft, killed 34 personnel, and injured over 100. That disaster, together with losses to enemy attack, drove the construction of revetments and shelters across South Vietnam. The airfield remains one of the hardest places to defend, a fixed target rich in aircraft, munitions, fuel, and technical staff. Aircraft now shelter behind revetments, hesco barriers, hardened aircraft shelters, and underground hangars. Old fortifications still earn their keep. The Yugo pyramid shelters built in the 1980s sheltered US personnel on the 8th of January 2020, when Iran fired 11 ballistic missiles at Ayn al-Asad Airbase in Iraq. For low-intensity conflict, comparatively obsolete fortifications endure, from small patrol bases to huge airbases such as Camp Bastion and Leatherneck in Afghanistan. Walls of gabion, sandbag, or simple mud still stop small arms and antitank weapons, though they remain vulnerable to mortar and artillery fire. The word fort has even drifted loose of its meaning. In modern American usage it often names a permanent military facility with no actual fortifications at all, set aside for barracks, administration, medical, or intelligence work. And not every fortification faces outward. Some, like the prison rooms of the Tower of London, were built to keep their inhabitants in.