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Now you see it, now you don't: what optical illusions tell us about our brains

Illusions can offer insights into how the visual system processes images.

Maurits Escher: where do the staircases lead?

The human brain is a network of about 20 billion neurons – nerve cells – linked by several trillion connections. Not to mention glial cells, which scientists used to think were inactive scaffolding, but increasingly view as an essential part of how the brain works. Our brains give us movement, language, senses, memories, consciousness and personality. We know a lot more about the brain than we used to, but it still seems far too complicated for human understanding.

Fortunately, the brain contains many small networks of neurons that carry out some specific function: vision, hearing, movement. It makes sense to tackle these simple modules first. Moreover, we have good mathematical models of nerve cell behaviour. In 1952, Alan Hodgkin and Andrew Huxley wrote down the “Hodgkin-Huxley equations” for the transmission of a nerve impulse, which won them the 1963 Nobel Prize in Medicine. We also have effective techniques for understanding small networks’ components and how they are linked.

Many of these simple networks occur in the visual system. We used to think that the eye was like a camera, taking a “snapshot” of the outside world that was stored in the brain like a photo stuck in an album. It uses a lens to focus an image on to the retina at the back of the eye, which functions a bit like a roll of film – or, in today’s digital cameras, a charge-coupled device, storing an image pixel by pixel. But we now know that when the retina sends information to the brain’s visual cortex, the similarity to a camera ends.

Although we get a strong impression that what we are seeing is “out there” in front of us, what determines that perception resides inside our own heads. The brain decomposes images into simple pieces, works out what they are, “labels” them with that information, and reassembles them. When we see three sheep and two pigs in a field, we “know” which bits are sheep, which are pigs, and how many of each there are. If you try to program a computer to do that, you quickly realise how tricky the process is. Only very recently have computers been able to distinguish between faces, let alone sheep and pigs.

Probing the brain’s detailed activity is difficult. Rapid progress is being made, but it still takes a huge effort to get reliable information. But when science cannot observe something directly, it infers it, working indirectly. An effective way to infer how something functions is to see what it does when it goes wrong. It may be hard to understand a bridge while it stays up, but you can learn a lot about strength of materials when it collapses.

The visual system can “go wrong” in several interesting ways. Hallucinogenic drugs can change how neurons behave, producing dramatic images such as spinning spirals, which originate not in the eye, but in the brain. Some images even cause the brain to misinterpret what it’s seeing without outside help. We call them optical illusions.

One of the earliest was discovered in Renaissance Italy in the 16th century. Giambattista della Porta was the middle of three surviving sons of a wealthy merchant nobleman who became secretary to the Holy Roman emperor Charles V. The father was an intellectual, and Giambattista grew up in a house in Naples that hosted innumerable mathematicians, scientists, poets and musicians. He became an outstanding polymath, with publications on secret codes (including writing on the inside of eggshells), physiology, botany, agriculture, engineering, and much else. He wrote more than 20 plays.

Della Porta was particularly interested in the science of light. He made definitive improvements to the camera obscura, a device that projects an image of the outside world into a darkened room; he claimed to have invented the telescope before Galileo, and very likely did. His De refractione optices of 1593 contained the first report of a curious optical effect. He arranged two books so that one was visible to one eye only and the other to the other eye. Instead of seeing a combination of the two images, he perceived them alternately. He discovered that he could select either image at will by consciously switching his attention. This phenomenon is known today as binocular rivalry.

Two other distinct but related effects are impossible figures and visual illusions. In rivalry, each image appears unambiguous, but the eyes are shown conflicting images. In the other two phenomena, both eyes see the same image, but in one case it doesn’t make sense, and in the other it makes sense but is ambiguous.

Impossible figures at first sight seem to be entirely normal, but depict things that cannot exist – such as Roger Shepard’s 1990 drawing of an elephant in which everything above the knees makes sense, and everything below the knees makes sense, but the two regions do not fit together correctly. The Dutch artist Maurits Escher made frequent use of this kind of visual quirk.

In 1832, the Swiss crystallographer Louis Necker invented his “Necker cube” illusion, a skeletal cube that seems to switch its orientation repeatedly. An 1892 issue of the humorous German magazine Fliegende Blätter contains a picture with the caption “Which animals are most like each other?” and the answer “Rabbit and duck”. In a 1915 issue of the American magazine Puck, the cartoonist Ely William Hill published “My wife and my mother-in-law”, based on an 1888 German postcard. The image can be seen either as a young lady looking back over her shoulder, or as an elderly woman facing forwards. Several of Salvador Dalí’s paintings include illusions; especially Slave Market With the Apparition of the Invisible Bust of Voltaire, where a number of figures and everyday objects, carefully arranged, combine to give the impression of the French writer’s face.

Illusions offer insights into how the visual system processes images. The first few stages are fairly well understood. The top layer in the visual cortex detects edges of objects and the direction in which they are pointing. This information is passed to lower layers, which detect places where the direction suddenly changes, such as corners. Eventually some region in the cortex detects that you are looking at a human face and that it belongs to Aunt Matilda. Other parts of the brain are alerted, and you belatedly remember that tomorrow is her birthday and hurry off to buy a present.

These things don’t happen by magic. They have a very definite rationale, and that’s where the mathematics comes in. The top layer of the visual cortex contains innumerable tiny stacks of nerve cells. Each stack is like a pile of pancakes, and each pancake is a network of neurons that is sensitive to edges that point in one specific direction: one o’clock, two o’clock and so on.

For simplicity, call this network a cell; it does no harm to think of it as a single neuron. Roughly speaking, the cell at the top of the stack senses edges at the one o’clock position, the next one down corresponds to the two o’clock angle, and so on. If one cell receives a suitable input signal, it “fires”, telling all the other cells in its stack: “I’ve seen a boundary in the five o’clock direction.” However, another cell in the same stack might disagree, claiming the direction is at seven o’clock. How to resolve this conflict?

Neurons are linked by two kinds of connection, excitatory and inhibitory. If a neuron activates an excitatory connection, those at the other end of it are more likely to fire themselves. An inhibitory connection makes them less likely to fire. The cortex uses inhibitory connections to reach a definite decision. When a cell fires, it sends inhibitory signals to all of the other cells in its stack. These signals compete for attention. If the five o’clock signal is stronger than the seven o’clock one, for instance, the seven o’clock one gets shut down. The cells in effect “vote” on which direction they are detecting and the winner takes all.

Many neuroscientists think that something very similar is going on in visual illusions and rivalry. Think of the duck and rabbit with two possible interpretations. Hugh R Wilson, a neuroscientist at the Centre for Vision Research at York University, Toronto, proposed the simplest model, one stack with just two cells. Rodica Curtu, a mathematician at the University of Iowa, John Rinzel, a biomathematician then at the National Institutes of Health, and several other scientists have analysed this model in more detail. The basic idea is that one cell fires if the picture looks like a duck, the other if it resembles a rabbit. Because of the inhibitory connections, the winner should take all. Except that, in this illusion, it doesn’t quite work, because the two choices are equally plausible. That’s what makes it an illusion. So both cells want to fire. But they can’t, because of those inhibitory connections. Yet neither can they both remain quiescent, because the incoming signals encourage them to fire.

One possibility is that random signals coming from elsewhere in the brain might introduce a bias of perception, so that one cell still wins. However, the mathematical model predicts that, even without such bias, the signals in both cells should oscillate from active to inactive and back again, each becoming active when the other is not. It’s as if the network is dithering: the two cells take turns to fire and the network perceives the image as a duck, then as a rabbit, and keeps switching from one to the other. Which is what happens in reality.

Generalising from this observation, Wilson proposed a similar type of network that can model decision-making in the brain – which political party to support, for instance. But now the network consists of several stacks. Maybe one stack represents immigration policy, another unemployment, a third financial regulation, and so on. Each stack consists of cells that “recognise” a distinct policy feature. So the financial regulation stack has cells that recognise state regulation by law, self-regulation by the industry, or free-market economics.

The overall political stance of any given political party is a choice of one cell from each stack – one policy decision on each issue. Each prospective voter has his or her preferences, and these might not match those of any particular party. If these choices are used as inputs to the network, it will identify the party that most closely fits what the voter prefers. That decision can then be passed to other areas of the brain. Some voters may find themselves in a state akin to a visual illusion, vacillating between Labour and Liberal Democrat, or Conservative and Ukip.

This idea is speculative and it is not intended to be a literal description of how we decide whom to vote for. It is a schematic outline of something more complex, involving many regions of the brain. However, it provides a simple and flexible model for decision-making by a neural network, and in particular it shows that simple networks can do the job quite well. Martin Golubitsky of the Mathematical Biosciences Institute at Ohio State University and Casey O Diekman of the University of Michigan wondered whether Wilson’s networks could be used to model more complex examples of rivalry and illusions. Crucially, the resulting models allow specific predictions about experiments that have not yet been performed, making the whole idea scientifically testable.

The first success of this approach helped to explain an experiment that had already been carried out, with puzzling results. When the brain reassembles the separate bits of an image, it is said to “bind” these pieces. Rivalry provides evidence that binding occurs, by making it go wrong. In a rivalry experiment carried out in 2006 by S W Hong and S K Shevell, the subject’s left eye is shown a horizontal grid of grey and pink lines while the right eye sees a vertical grid of grey and green lines. Many subjects perceive an alternation between the images, just as della Porta did with his books. But some see two different images alternating: pink and green vertical lines, and pink and green horizontal lines – images shown to neither eye. This effect is called colour misbinding; it tells us that the reassembly process has matched colour to grid direction incorrectly. It is as if della Porta had ended up seeing another book altogether.

Golubitsky and Diekman studied the simplest Wilson network corresponding to this experiment. It has two stacks: one for colour, one for grid direction. Each stack has two cells. In the “colour” stack one cell detects pink and the other green; in the “orientation” stack one cell detects vertical and the other horizontal. As usual, there are inhibitory connections within each stack to ensure a winner-takes-all decision.

Following Wilson’s general scheme, they also added excitatory connections between cells in distinct stacks, representing the combinations of colour and direction that occur in the two “learned” images – those actually presented to the two eyes. Then they used recent mathematical techniques to list the patterns that arise in such a network. They found two types of oscillatory pattern. One corresponds to alternation between the two learned images. The other corresponds precisely to alternation between the two images seen in colour misbinding.

Colour misbinding is therefore a natural feature of the dynamics of Wilson networks. Although the network is “set up” to detect the two learned images, its structure produces an unexpected side effect: two images that were not learned. The rivalry experiment reveals hints of the brain’s hidden wiring. The same techniques apply to many other experiments, including some that have not yet been performed. They lead to very specific predictions, including more circumstances in which subjects will observe patterns that were not presented to either eye.

Similar models also apply to illusions. However, the excitatory connections cannot be determined by the images shown to the two eyes, because both eyes see the same image. One suggestion is that the connections may be determined by what your visual system already “knows” about real objects.

Take the celebrated moving illusion called “the spinning dancer”. Some observers see the solid silhouette of a dancer spinning anticlockwise, others clockwise. Sometimes, the direction of spin seems to switch suddenly.

We know that the top half of a spinning dancer can spin either clockwise or anticlockwise. Ditto for the bottom half. In principle, if the top half spins one way but the bottom half spins the other way, you would see the same silhouette, as if both were moving together. When people are shown “the spinning dancer”, no one sees the halves moving independently. If the top half spins clockwise, so does the bottom half.

Why do our brains do this? We can model that information using a series of stacks that correspond to different parts of the dancer’s body. The brain’s prior knowledge sets up a set of excitatory connections between all cells that sense clockwise motion, and another set of excitatory connections between all “anticlockwise” cells. We can also add inhibitory connections between the “clockwise” and the “anticlockwise” cells. These connections collectively tell the network that all parts of the object being perceived must spin in the same direction at any instant. Our brains don’t allow for a “half and half” interpretation.

When we analyse this network mathematically, it turns out that the cells switch repeatedly between a state in which all clockwise cells are firing but the anticlockwise ones are quiescent, and a state in which all anticlockwise cells are firing but the clockwise ones are quiescent. The upshot is that we perceive the whole figure of the dancer switching directions. Similar networks provide sensible models for many other illusions, including some in which there are three different inputs.

These models provide a common framework for both rivalry and illusion, and they unify many experiments, explain otherwise puzzling results and make new predictions that can be tested. They also tell us that in principle the brain can carry out some apparently complex tasks using simple networks. (What it does in practice is probably different in detail, but could well follow the same general lines.)

This could help make sense of a real brain, as new experiments improve our ability to observe its “wiring diagram”. It might not be as ambitious as trying to model the whole thing on a computer, but modesty can be a virtue. Since simple networks behave in strange and unexpected ways, what incomprehensible quirks might a complicated network have?

Perhaps Dalí, and Escher, and the spinning dancer can help us find out. 

Ian Stewart is Emeritus Professor of Mathematics and Digital Media Fellow at the University of Warwick

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Brothers in blood: how Putin has helped Assad tear Syria apart

The Syrian catastrophe has created the worst humanitarian crisis since the end of the Second World War. And the world watches helplessly as Putin and Assad commit war crimes.

Sometimes we know the names. We know Omran Daqneesh, the five-year-old boy who, covered in mud and dust, was pictured on the back seat of an ambulance in the aftermath of an air attack. We know his name because pictures and a video of him were released on social media and travelled around the world. The outrage that followed was widespread and sincere, the image of the dazed little boy seeming to symbolise the greater plight of the beleaguered residents of Aleppo. But then the moment passed. Few will know that a few days later doctors announced that Omran’s elder brother Ali, who was injured in the same air strike, had died from his injuries. He was ten.

Sometimes we know the names of the babies pulled from the rubble of collapsed buildings – occasionally alive, but often dead; or the names of the children weeping over lost parents; or the women grieving over lost husbands and children; or the elderly simply waiting (and sometimes wanting) to die.

We know Bana Alabed, the seven-year-old girl trapped inside Aleppo whose Twitter account has gone viral in recent weeks. “Hi I’m Bana I’m 7 years old girl in Aleppo [sic],” reads the on-page description. “I & my mom want to tell about the bombing here. Thank you.”

A series of pictures depicts Alabed and her mother, Fatemah, struggling to live as normal a life as possible, one showing the little girl sitting at an MDF desk with a book. Behind her, in the corner, is a doll. “Good afternoon from #Aleppo,” says the caption in English. “I’m reading to forget the war.”

The conflict, however, is never far away. Alabed, whose mother taught her English, has repeatedly tweeted her own fears about dying, followed by stoic messages of defiance whenever the immediate threat of an impending air strike passes. On the morning of 3 October, her words were simply: “Hello world we are still alive.” On 17 October, Fatemah tweeted: “The airstrikes ended in the morning, all the last night was raining bombs.”

But in most cases we never know the names of the victims of air assaults led by Presidents Bashar al-Assad and Vladimir Putin. One of the most haunting images to emerge in recent weeks was that of a mother and child, killed while sleeping in the same bed. The scene had an eerily preserved-in-amber feel to it: a snapshot of snatched lives, frozen in the act of dying. Pictures of ruined buildings and distraught civilians have become routine now, holding our attention briefly – if at all.

As many as 500,000 people are believed to have been killed since the beginning of the Syrian uprising in early 2011. According to a report released in February this year by the Syrian Centre for Policy Research, a further 1.9 million have been wounded. Taken together, those figures alone account for 11.5 per cent of Syria’s pre-revolutionary population. Combine that with the number of Syrians who have been displaced – more than ten million (almost 50 per cent of the population) – and the sheer scale of the disaster becomes apparent.

The conflict has become the worst humanitarian crisis since the Second World War. Today it centres on Aleppo, in north-west Syria, one of the oldest continuously inhabited cities in the world, and a cradle of human civilisation. Various conquerors from the Mongols to the French have fought battles there but none, so it would seem, has been quite as ruthless or committed to the city’s annihilation as Bashar al-Assad.

Aleppo remains the most significant urban centre to have been captured by the anti-Assad rebels, most of whom will (by now) be strongly influenced by an Islamist world-view. Indeed, the most prominent fighting groups on the rebel side are overwhelmingly Islamist in their troop composition and beliefs, a sad marker of Western failures to support secular forces that led the anti-regime resistance in the incipient phases of the uprising.

Yet Aleppo remains too important to fail. Although rebel forces succeeded in capturing only half of the city – the western side remained firmly in the control of the regime – the symbolism of anti-Assad forces holding ground in Syria’s second city (which also served as the country’s economic hub) has buoyed the rebel movement.

Assad is more brazen and bullish than at any other point since eastern Aleppo fell into rebel hands in July 2012. That optimism is born of a strategy that has already worked in other parts of the country where the regime’s troops have slowly encircled rebel-held areas and then sealed them off. Nothing can leave, and nothing can enter. Once the ground forces seal off an area, an aerial campaign of barrel bombs and missile attacks from both Syrian and Russian fighter jets inevitably follows.

To get a sense of just how terrible the aerial campaign has been, consider that the United States accused the Russian air force of potential war crimes when a UN aid convoy was bombed just west of Aleppo last month. It was carrying food and medicines when it was hit. Since then, the UK and France have said that Russia’s bombardment of Aleppo amounts to a war crime.

Putin’s support has come as a boon to Assad ever since Russia formally entered the conflict in September 2015. Despite his administration already using Iranian forces and aligned groups such as the Lebanese Shia militia Hezbollah, rebels had continued to make significant gains throughout the early months of 2015. The most important of these was the capture of Idlib city, 40 miles from Aleppo, which presented Assad with two problems. The first was that it dented the official narrative of revanchist military successes by his forces. The ­second was that it handed the rebels power in a province adjoining Latakia Governorate in the west, where Syria’s Alawites are largely concentrated (Russia has an airbase in an area south-east of the city of Latakia). The Alawites are a heterodox Shia sect to which the Assad family belongs, and which forms the core of their support base.

Keen to reverse these gains – and others made elsewhere – Assad enlisted Putin, given Russia’s long-standing interests in, and ties to, Syria. The Kremlin has long regarded Syria as an important ally, and has served as the country’s main arms supplier for the past decade. There are important assets to preserve, too, such as the Russian naval base in the port city of Tartus on the Mediterranean, which was first established during the Soviet era.

For his part, Putin has felt emboldened by events. The world is changing – not just in the Middle East and North Africa, where the
contours of power continue to be recast, but also closer to home in Ukraine, where the pro-Russian president Viktor Yanukovych was overthrown in 2014.

The West is still haunted by the 2003 invasion of Iraq and has been reluctant to be drawn too deeply into the Syrian War. In 2013, the Assad regime used chemical weapons against its own people. This was a violation of President Barack Obama’s so-called red line against the use of chemical weapons, but no retaliatory action came and there was nothing to prevent the Kremlin from using force to shape events in Syria – as it had done in Ukraine.

All of this has marked a new phase of brutality in a conflict already noted for its barbarism. Civilians who avoid death from combined Russo-Syrian air assaults suffer under Assad’s strategy of “starve or submit”, in which supplies are withheld from besieged areas, slowly choking off those ­inside. It has been used to devastating effect against civilians in towns such as Madaya and in Daraya, on the outskirts of Damascus, both of which fell to government control after being sealed off from the outside world for several years. Such a strategy is not designed to deliver quick victories, however. Consider how the residents of Daraya defied Assad’s forces for four years before capitulating in August 2016.

Assad and his allies (Putin, Iran, Hezbollah) have decided to punish and brutalise, deliberately, civilian populations in rebel-held areas. To invert the famous aphorism attributed to Chairman Mao, they hope to dredge the sea in which the revolutionaries swim. And so, it is the 300,000 residents of eastern Aleppo who must suffer now.




It’s easy to lose track of precisely what is happening in the Syrian War as parcels of land swap hands between rebels and the regime. Assad’s forces first began encircling Aleppo at the start of July this year and succeeded in imposing a siege by the middle of that month, after cutting off the last of two rebel-controlled supply routes into the city. The first was the Castello Road, which leads from the town of Handarat into the north-western part of ­rebel-controlled territory. The second route, via the Ramouseh district (which led into the south-western end of the city), had already been sealed off.

The closure lasted for roughly four to five weeks before the rebels re-established access. Aleppo is too important for them, and the siege has forced various groups to work together in breaking it. The effort was led by Jaish al-Fateh (JaF, the “Army of Conquest”), an umbrella group and command structure for several of the most prominent jihadist and Islamist groups operating in northern Syria. JaF also co-ordinated the Idlib military campaigns. One of its key members is Jabhat Fateh al-Sham (JFS, “the Syrian Conquest Front”), which was previously known as Jabhat al-Nusra (JaN or “the Supporters’ Front”) and was recognised as al-Qaeda’s official chapter in Syria.

Several months before the regime began its assault on Aleppo, rebel groups in the north recognised the deteriorating situation there, stemming principally from Russian air strikes. As a result, al-Qaeda urged the various factions to merge and work together to counteract not just Assad, but also Putin. Even the global leader of al-Qaeda, Ayman al-Zawahiri, issued a speech last May titled “Go Forth to Syria”, in which he called on all fighting groups to unite in order to consolidate their control across the north. This opened the way at the end of July for Jabhat al-Nusra to declare that it was formally severing its links with al-Qaeda. It “rebranded” as Jabhat Fateh al-Sham.

There are two reasons for doing this. The first is to erode partisanship among the Islamist groups, forcing them to set aside differences and narrow their ambitions in favour of the greater goal – in this case, the breaking of the siege of Aleppo, while also deepening rebel control across the north. The second aim of rebranding is to win popular support by portraying themselves as fighting in the service of ordinary civilians.

Groups such as JFS and others are succeeding in both of these goals. Responding to the abandoned and assaulted residents of Aleppo, they have repeatedly demonstrated their commitment to alleviating the humanitarian crisis. Much of their messaging echoes this theme. The group’s English-language spokesman is Mostafa Mahamed, an Egyptian who previously lived in Australia. “[JFS] is deeply embedded in society, made up from the average Syrian people,” he explained on Twitter, after the group decoupled from al-Qaeda. “We will gladly lay down our lives before being forced into a situation that does not serve the people we are fighting for . . . jihad today is bigger than us, bigger than our differences.”

It is indisputable that this ethos of “fighting for the people” has endeared the group to civilians living in besieged areas – even when those civilians don’t necessarily agree with the full spectrum of its religious beliefs or political positions. That goodwill was only reinforced when the group helped break the siege of Aleppo (in which approximately 500 rebels were killed) in August, if only for a few days. Assad reasserted control within a week, and entrapped the residents again in the middle of that month. The rebels are now planning how to break the siege decisively, but have not yet launched a major counteroffensive.




A freelance American journalist and film-maker, Bilal Abdul Kareem, who has reported on rebel movements inside Syria more intimately than most, has found himself among those trapped inside eastern Aleppo since the siege was restored seven weeks ago. “We came here expecting a two- or three-day trip,” he told me during an interview over Skype.

Life inside is becoming insufferable for civilians, Abdul Kareem said; every building is potted and scarred by shrapnel damage. Those whose homes remain standing are the lucky ones. “Your day consists of nothing,” he said. “There’s no work, there’s no fuel, no industrial zone, no food to sell. ­People sit around and chit-chat, drink tea, and that’s all they do.”

Food supplies are already running low, with most people limiting themselves to basics of chickpeas and groats – crushed grains such as oats or wheat. Sealed off from the rest of the world, those inside preoccupy themselves with survival and wait for the next wave of attacks.

It is tempting to ask why the inhabitants of Aleppo did not flee when they had the chance. Indeed, the Assad regime routinely accuses the rebels of preventing civilians from leaving besieged areas, though there is no evidence to support this view. On 17 October Russia and the Syrian regime said they would halt their bombardment for eight hours on 20 October to allow rebels and civilians to evacuate the city.

In truth, what choice do the civilians have? Most do not trust Assad and they are therefore unwilling to move into regime-administered areas. The alternative is to become refugees, with all the uncertainties and trials associated with that. For instance, refugees have found themselves subject to sectarian violence in Lebanon, and they have few opportunities to find employment in Lebanon, Turkey or Jordan, the three countries where most of the fleeing Syrians have found shelter.

For them, merely to exist in rebel territory is an act of defiance, which is precisely why Assad’s forces make no effort to distinguish between combatants and civilians in rebel areas. To be present is a crime.

The effects of this have been devastating. A spokesman for the Syrian American Medical Society told Middle East Eye, an online news portal, that in July, Syrian and Russian jets had hit medical facilities in rebel-held territory every 17 hours.

Only a few hospitals and medical staff remain. The physical conditions are primitive and perilous. Doctors work in makeshift facilities – a former flat, a commercial garage – which makes them unable to provide anything beyond basic emergency care. In-patient facilities are non-existent, not just because of high demand from those newly injured in fresh attacks, but also from fear that the facility itself will be targeted. “People are literally shuffled out of the hospital with IV [intravenous drips] in their arms,” Abdul Kareem says.

The West’s indifference to all this – coupled with its occasional pious pronouncements and diplomatic dithering – has squandered any goodwill Washington might once have had among Syria’s beleaguered civilians. When Sergey Lavrov, Russia’s foreign minister, and John Kerry, the US secretary of state, agreed a ceasefire in September it lasted barely two days because they overlooked the fears of those trapped inside eastern Aleppo.

The deal had stated that no party would try to capture any new territory. That might seem reasonable enough but given that the ceasefire came into effect just days after Assad re-established the siege of Aleppo, those on the inside were being asked, in effect, to acquiesce to their own starvation.

Deprived of food and medication, no one trusted Assad to negotiate access in good faith, especially after he thwarted UN efforts to deliver aid. “People saw it as a conspiracy,” Abdul Kareem told me. Moreover, there were no significant groups inside eastern Aleppo that claimed to have accepted the terms of the ceasefire in the first place. Kerry had negotiated on their behalf without approval and without securing any humanitarian concessions.

“What planet are these people on?” Abdul Kareem asked. “[Do] they think people will turn on their protectors, for people who didn’t do them any good? They look to JFS and Ahrar [Ahrar al-Sham is one of the Islamist groups fighting in JAF]. Western intervention is pie in the sky.”

The rise of these reactionary rebels is a direct result of liberal elements not being strongly supported at any stage in the conflict. Left to fend for themselves, many have deserted their cause. Those who have persisted not only risk the constant threat of being killed by Russo-Syrian bombs, but are also at threat from jihadist elements operating in rebel areas. That much was clear when remnants of the secular opposition protested against the leader of JFS, Abu Mohammed al-Golani, in the southern Idlib town of Maarat al-Nouman earlier this year. Many of those who did were arrested by jihadists and intimidated into silence.

Whereas liberals are fragmented and frayed, the Islamist rebels continue to coalesce into an ever more coherent unit. The overwhelming might of Russian airpower has convinced them of the need to form a united front in order to pool their resources and co-ordinate their efforts. That is one of the reasons why a jihadist group called Jund al-Aqsa (“Soldiers of al-Aqsa”) announced early this month that it was disbanding and being absorbed into JFS.

Herein lies the real story of how Aleppo – and, indeed, Syria itself – has been delivered to the jihadists. A conspiracy of all the external parties has forged a menacing millenarian movement that is embedded in civil society and communities across the north. Whether Aleppo falls or not, the jihadists will endure.

Shiraz Maher is a contributing writer for the New Statesman and a member of the war studies department at King’s College London

Shiraz Maher is a contributing writer for the New Statesman and a senior research fellow at King’s College London’s International Centre for the Study of Radicalisation.

This article first appeared in the 20 October 2016 issue of the New Statesman, Brothers in blood