If asked to picture a castle, most people would imagine a historical artefact, a museum piece, or maybe a fantastical Disney confection. What they would not imagine is a piece of currently relevant military engineering. Nevertheless, in January 2021 it was reported that French forces fighting Islamist rebels in Mali had constructed two new forts, one at Labbezanga, a small riverport village on the Niger River and the other at Menaka, a town about 200 kilometres away, also near the Niger border. Normally, the expansion of the world’s existing stockpile of fortified outposts in far-off dusty places would not be newsworthy. But these Malian forts speak to a vast and growing, yet little remarked on, trend – ever-increasing global fortification, both by the military and civil organisations.

Governments at all levels, private companies, communities both large and small, even criminal entities, are all building fortresses of one sort or another at an astonishing pace. The fact is that ours is a physically guarded age as much as any time since the castellated days of yore. Modern life is conducted within concentric layers of fortification. True, a great deal of it is hidden in plain sight, designed to look like something else, and some of it, such as surveillance systems, is intangible, but most of it is tangible—and it is everywhere.

Moreover, fortification today is good business, outstripping in size other major categories of military investment, and growing while others are shrinking.

Mali’s two new forts may not be the magical fairy tale castles of cultural imagination, but they are nevertheless eye-catching, as, in an obvious nod to the seventeenth-century French military engineer Sébastien Le Prestre de Vauban they are constructed in a ‘star fortress’ pattern. It’s well over two centuries since this form of architecture was at its peak, but our modern guarded age is full of similarly inventive structures and products including barriers, border walls, guard towers, and armoured gatehouses.

And not only does a very large fortification market exist; it consists of a huge range of products. To give an indication of scale, the IFSEC Global Directory (a UK-based listing of security sector manufacturers and service providers) currently lists 355 companies selling ‘perimeter security’ products from all manner of barriers and bollards to blast resistant doors, with a further 709 different companies marketing various surveillance systems to go along with them. The perimeter security business alone is estimated now to be worth $61 billion annually, with the potential to rise to $96.5 billion by 2026. For comparison, the global estimated annual value of armoured vehicle sales, a more obvious military product, was $25.5 billion in 2018. This fortification speaks to the globally-perceived threat from mass terrorism – and much more besides.

But first, let us begin with forts. The intrinsic durability of star fortresses is such that the global landscape is still littered with their remains. From the Canadian high Arctic where the Prince of Wales Fort can be found, to the tropics, such as Sri Lanka’s Jaffna fort, which was the scene of a fifty-day siege as late as 1995, almost 400 years after it was built. In its classic form, this type of fortress is noteworthy for the meticulous geometry of its interlocking bastions and outer works, including ditches (often flooded) and long sloping glacis all designed to maximise the impact of defensive fire while resisting the blows of siege artillery. Often, they remain in more gentle military use today as barracks, headquarters, or residences of high officials, but mostly they have blended picturesquely into a becomingly placid semi-urban scene.

It is doubtful, though, that tourists will be flocking to these new Malian fortresses to admire their aesthetic qualities. Indeed, aside from their basic star shape, which is pleasing from the air, they share little else in common with the grand Renaissance gun fortresses—not least, the surface-mounted structures lack the defining thick glacis. That is no surprise; they aren’t designed to defeat siege artillery but to act as a base of operations against different sorts of threats. That does not make them unimportant. Indeed, they are worth a closer look, not because of their seemingly antique morphology, but because they are fine examples of a military architecture that is incredibly current, widespread, and surprisingly little-remarked upon.

The trick is to look at what the fortresses are built from rather than their shape. The latter is essentially an incidental quality, in this case a bit of a fashion statement. The former is quite a bit more interesting. What if Ikea and Lego combined their respective design philosophies for making furniture and toys in order to make mass-market kits for building life-size forts? You might expect the result would be something of utilitarian design available in a range of standardised, modular and interlocking shapes, flat-packable for easy shipping, durable (and reusable) while also being relatively cheap. The user could combine these pieces in whatever forms their imagination desired.

In open terrain like that of Mali where there’s no extra cost of preparing the already flat ground, engineers can let inspiration run riot and build star shapes if they want; but more regular polygons with adequate towers would do just as well, particularly for very big bases as seen in Britain’s Camp Bastion in Helmand, Afghanistan. More congested or contorted landscapes produce smaller forts that trace the terrain in irregular shapes rather like Iron Age hillforts, as at Combat Outpost (COP) Restrepo in the Korengal Valley.

In some cases, such as at gatehouses, which need to limit the potential damage of vehicle-borne bombs, a fortified switchback or serpentine shape that slows vehicles and prevents direct approaches to entrances is called for. The potential combinations are very great, depending on tactical factors such as terrain and the nature of the supposed threat, as well as the primary consideration of cost and the rarer consideration of aesthetics.

One of the most recognisable and interesting products is HESCO bastion, manufactured by a British company based in Bradford. It is essentially a gabion (a large basket filled with earth and stone) a very old piece of military technology. Think of it as a big building block. In the old days these were constructed out of wicker and used to provide protection from enemy gunfire during sieges.

The modern version invented by British entrepreneur Jimi Haseldon, initially as an anti-erosion barrier (for which it is still in wide civilian use), is made of hinged wire mesh with a sturdy geotextile lining. Easy to ship and to set up, given an adequate supply of local dirt a handful of soldiers with a front-end loader can stack them into a workable fortress in a few hours. It is a commendable piece of modern design, rather like Mies van der Rohe’s famous Barcelona chair—a reinvention of an old and familiar thing in a new and current way.

What HESCO lacks in grandeur it makes up for in utility. Under fire, loose packed earth has huge damage resistance as opposed to more solid constructions which often shatter and spall dangerous fragments. In addition to military usage, it is employed heavily in the humanitarian sector, for example, as a safe haven for vulnerable aid workers, in industry for the protection of critical infrastructure, such as refineries, and generally as a rapidly deployable perimeter protection system with a multitude of uses.

The forms in which HESCO forts can be built are as varied as the combination of imagination, tactical exigency, and cost allows. It is to the ‘War on Terror’ what the Huey helicopter was to Vietnam—the ever-present backdrop to a million war photos. The scale of civil governmental and NGO use is also noteworthy. For example, according to the latest available accounts of the United Nations Procurement Division in 2013-14 it purchased around $75 million worth of HESCO gabions, security barriers, and prefabricated fortifications.

HESCO is by no means the only significant military engineering product in increasingly wide use. The sector is burgeoning with other reinvented fortification technologies from portable marching forts to modular armoured guard posts, to an assortment of concrete T-walls (originally a highway safety device) for protection against low-trajectory weapons and blast mitigation. The last are frequently used in base building, but their most remarkable recent employment is in urban counterinsurgency. Repurposed as barriers separating warring neighbourhoods, they are dubbed ‘peace walls’, and proved highly useful in reducing violence in Baghdad in 2008. Unfortunately, as can be seen in Belfast where the British started employing them nearly fifty years ago, they tend to become permanent.

For obvious reasons, fortifications are particularly evident in Afghanistan where every army base, government centre, transport hub, and much else besides, is girded by walls and ditches, blast barriers, guard towers and armoured gatehouses. The same may be said of practically any contemporary conflict zone. Mogadishu, Somalia where the fortified ‘green zone’ around the airport effectively provides an armoured cantonment for international visitors is a good example too; but looking at Afghanistan alone yields some useful generalisations.

The first is that fortified life is not the exception to the rule of contemporary military affairs but the default experience of war, if not always for the locals, then nearly always for foreign troops, diplomats and other officials. Most troops on operational deployment – 90 per cent or more – never or very rarely leave them. They arrive by air into a fortified cantonment somewhere, perform their duties, and depart the same way they came without ever having left its confines. The cost of a big fortified base is in the hundreds of millions of dollars. Kandahar Airfield, for instance, was a mid-size town with a daytime population of 20,000 (dropping to about 12,000 at night when local workers had gone home) with an infamous boardwalk of shops and restaurants at its height in 2010. The US Embassy in Kabul was reported to have cost $1.5 billion to build and secure.

It would certainly be hard to have missed the fortified quality of contemporary military operations during the recent chaotic withdrawal of NATO from Afghanistan. The backdrops to desperate scenes of people attempting to flee the Taliban via Hamid Karzai International Airport were walls decked with razor wire, sewage-laden moats, and gates loomed over by armoured towers. It is arguable that miasmic debacle did not become a twenty-first century Alamo, or Dien Bien Phu, though if the Taliban had contested the withdrawal by targeting the vulnerable airfield it could have turned out that way.

On the way to the airport, American diplomats lifting off in helicopters from their embassy compound might have glimpsed the site of the old British Sherpur cantonment a half-mile away. Abandoned after a siege in 1879 during the Second Anglo-Afghan War it is now a military cemetery, known locally as Kabre Gora or the ‘foreigner’s graveyard’. Truly, as Mark Twain quipped, while history rarely repeats itself exactly, it often ‘rhymes.’

This suggests another generalisation: the huge continuity in fortification, often remarked upon by soldiers and other visitors. Most fortresses are built on or in the shadow of older ones, for largely the same reasons, and to much the same result. The landscape of the most recent Afghan war was comprised of layer after layer of fortification. Jury-rigged NATO castles were often built around the remains of Soviet fortified outposts, which in turn were heaped on the site of derelict British fortresses, some of which rested on even older ones built by or against invaders ranging from the Mongols to the Macedonian Greeks.

Combat Outpost (COP) Coleman in the eastern Kunar province was built around a nineteenth-century British border fortress, while COP Castle (the hint is in the name) in Helmand province incorporated a twelfth-century castle once besieged by Genghis Khan’s army. Near Qalat City in Zabul province soldiers at two Forward Operating Bases named Langman and Apache guarding Highway 1 (which runs along the old Silk Road) were overlooked by a fortress built by the army of Alexander the Great. Marines based at Fort Barcha in Garmsir district, Helmand, renamed their decomposing mudbrick outpost ‘Castle Greyskull’ in a nod to the fictional 1980s Masters of The Universe fortress.  It had previously been occupied by the Soviets who extensively tunnelled out and added to a pre-existing fortress of uncertain vintage. A full list would be very long indeed.

Finally, the scale of fortification is also noteworthy. By 2010 it was reported that Afghanistan had 700 fortified bases and outposts, approximately 300 of them held by the Afghan national army and police—all now abandoned or held by the Taliban. Time awaits the arrival of a new imperial adventure, no doubt, to add another layer of strategic stratigraphy.

This impressive number, however, is exceeded by the efforts of neighbouring Pakistan which is estimated by the end of 2021 to have built (or recommissioned) as many as 1,000 forts and border posts along its border with Afghanistan. These are but one part of a fortified strategic complex that includes approximately 1,500 miles of dual chain link and barbed wire fencing, plus a 400-mile-long, eleven-feet-deep and fourteen-feet-wide ditch, combined with an array of cameras and other electronic sensors, built at a reported cost of $500 million. The Afghanistan-Pakistan region is impressively heavily fortified – but similar levels of effort are observable elsewhere in the world too.

There has, of course, been a good deal of attention paid to such continuous frontier fortifications since the 2016 US presidential election of Donald Trump on a campaign promise to build (more exactly to extend and reinforce) a wall on the US-Mexico border. The contentious politics on this issue have focused largely on migration policy and not military affairs. There is good reason for that. Some peripheral linear barriers have little or nothing to do with military defence — America’s Mexican border is a case in point. Likewise, Europe’s anti-migration barriers, which are hardly less extensive than Trump’s proposed wall, have had mixed success, though their symbolic power as a rebuke of borderlessness, a central idea of globalisation, is great.

These realities distract, however, from the fact that some of these huge linear barriers are objects of substantial and creative military engineering serving the national security strategy of at least a dozen nation states around the globe today. What has been happening for a few decades, although rapidly hastening in recent years, is fortification on a scale that exceeds by an order of magnitude the famous efforts of the Roman Emperor Hadrian in north Britain and rivals that of the Great Wall of China—and nearly all of that in the space of a generation or two.

Perhaps the most well-known is Morocco’s Western Sahara Wall, often referred to as the ‘Sand Wall’. The appellation is not surprising as the vast majority of its 1,600-mile length is of a sand berm and ditch construction, not dissimilar in form from the ancient Offa’s Dyke in Britain or the traces of the Roman Limes still detectable across Germany between the Rhine and Danube rivers. It is also, however, somewhat misleading as to the degree of effort and sophistication of its construction. Dotted with relentless regularity every three to five miles along the Sand Wall are forts manned by as many as 100,000 Moroccan soldiers. The gaps, moreover, are covered by high fences in many places, several layers of barbed wire, a range of electronic surveillance devices, and approximately seven million land mines. By any measure this is a serious work of fortification that has occupied the bulk of national military effort for the last thirty years.

It is sometimes said that so vast is the Great Wall of China it is visible from space. Alas, this is untrue. Linear fortifications, while often very long, are relatively thin, and this lack of depth is one reason they tend to lack resilience against high-intensity threats. As it happens, though, the fortification of the border between India and Pakistan can be seen from orbit, at least at night, because approximately two thirds of its 2,000 miles is constantly floodlit – at enormous cost. The 3,000 mile India-Bangladesh border has also been progressively fortified in a multi-decade project first proposed by Prime Minister Indira Gandhi in the early 1980s a few years before she was assassinated. Although primarily an anti-migration barrier, it is heavily policed—between 2001 and 2010 Indian security forces are estimated to have shot 900 Bangladeshis crossing the frontier. Casualty figures for the most recent decade are not available.

The number of such barriers in the world today varies according to how and what one counts. A few, such as that between South Africa and Mozambique, are rudimentary and effectively now derelict for lack of money, though the perceived need for them has not diminished. Some such as that between Kenya and Somalia are seemingly half-built or mired in delay. The so-called ‘European Rampart’ on Ukraine’s border with Russia, now scheduled for completion in 2025, a decade after works began, is another example; others such as the North & South Korean DMZ are thoroughly militarised to the point of practical impregnability outside of a major war. Indubitably, though, there are a great many of them, and they are found on all continents barring Australia and Antarctica. In recent years, among the largest and most technically sophisticated have been built in the Middle East, inter alia by Turkey on its border with Syria, and by Saudi Arabia initially on its border with Iraq and now along the Yemeni border as well.

Walls sometimes excite people and sometimes bore them so that they sink beneath notice, and often they do both at the same time. There is a beguiling simplicity to them — after all, often what we are talking about are literally just piles of dirt. All the same, they carry a symbolic importance that increasingly people perceive, perhaps unconsciously, and they hold portentous, even ominous, messages.  Ours is supposed to be a ‘liquid’ age of global interdependence, digital connectedness, ‘frictionless’ flows of goods and people, and constant changes no longer bound (or even slowed down) by the resistance of space. Scholars have declared this to be the zeitgeist as far back as the 1960s. ‘The world is flat’ is how Thomas Friedman’s bestselling book on globalisation once put it, which is to say it is meant to be inimical to the barriers, obstacles, and fortresses of more guarded and less open times.

Military fortification, more specifically, is supposed, in the words of Ian Hogg’s Fortress, a well-regarded history of military defence, to be a ‘redundant science’ largely out of step generally with the conditions of modern life, and specifically with the dilemmas of modern warfare. The radically lethal firepower disposed by industrial societies leaves scant role for static fortifications, it is said. This is why in military affairs, and politics generally, when someone wishes to describe a thing as hidebound, retrograde, and/or doomed to failure they so often invoke the failure of France’s Maginot Line against the German blitzkrieg or declaim a ‘fortress mentality.’

The problem is that is all wrong. If you pay more attention to what is done, as opposed to what is said, it is apparent that contemporary warfare is exceedingly positional in character and increasingly fixed around fortified strategic complexes of great size, complexity, and engineering ambition—all of which come at significant expense and require not insignificant ingenuity. Moreover, the urge to fortify oneself and ones property is not confined to the military sphere.

The increasing fortification of the urban landscape is a gigantic aspect of the global societal response to the perceived threat of mass terrorism. This, along with the massive corporate and government investment in civil infrastructure hardening, especially of transportation and data networks, require a great deal more study, thought, and research if we are truly to understand the age we are living in.