All photos by author.

The cold numbers are the first thing that hit you. Figures telling of a human catastrophe on a scale hard to compute. Suffering on a level to which any rational response seems inadequate – 470,000 people killed, according to the latest estimates; 11.5 percent of the population injured; 45 percent of a country of 22 million made homeless; 4 million refugees and 6.36 million internally displaced persons. Life expectancy is down from 70.5 years in 2010 to an estimated 55.4 years in 2015. Welcome to the Syrian civil war.

For those of us who have covered the war closely, these are not just numbers in black and white. They have behind them searing images and memories impossible to erase.

I remember the throngs of refugees in the olive groves close to the border fence north of Aleppo in the summer of 2012. The battle for the city was raging at its full murderous strength a few kilometers to the south. The refugees, mostly Sunni Arabs, were trying to find a place safe from the destructive intentions of Bashar Assad's air force. They had no way to get into Turkey. Their forlorn hope was to take their families as close as possible to the border fence. They believed that the Syrian Air Force would not dare to bomb so close to the powerful northern neighbor.

Whole families with small children ‒ some people terribly wounded by the bombings ‒ living in the olive groves with neither shelter nor provisions. But I had been in Aleppo city, too, and I knew that their calculation made sense. Inside the city, the barrel bombs were falling without discrimination. Houses, buildings, lives turned into nothing.

The Syrian civil war is the greatest catastrophe to hit the Levant since World War II.

This is what the figures are made of. For five years, this is what the lives of Syrians have looked like. It is the greatest catastrophe to have hit the Levant since World War II.

Few people saw the war coming. For a moment, it looked as though the wave of regional change would pass Syria by. The prison-house state constructed by the Ba'ath Party had strong walls, after all. Its residents seemed too cowed, too intimidated to challenge their dictator.

Assad himself, in a strange interview given to the Wall Street Journal, published January 31, 2011, explained why, in his view, Syria had not and would not experience instability. "We have more difficult circumstances than most of the Arab countries but in spite of that Syria is stable," the dictator said. "Why? Because you have to be very closely linked to the beliefs of the people. This is the core issue. When there is divergence between your policy and the people's beliefs and interests, you will have this vacuum that creates disturbance."

Here was the language of the Arab nationalist police state in all its self-assurance and blindness. The prisons full of political prisoners. The citizenry cowed by an all-embracing structure of surveillance and repression. And on top of it all, the "president" blithely insisting to his compliant Western interviewer that the stability was the result of a kind of tacit contract of consent between the regime and the people.

It couldn't hold. And, of course, it didn't. As nemesis follows hubris, so in March 2011, demonstrations by schoolchildren in Dera'a province were brutally repressed by the local security forces. A boy called Hamza al-Khatib who was murdered in custody became the symbol for the protests. The unrest spread to other Sunni Arab parts of the country – Homs, Hama, Banias. Assad, whose rule, he had claimed, rested on the unspoken consent of his people, rapidly and predictably abandoned any such nonsense and sought simply to drown the spreading protests in the blood of the protesters.

By summer, the stage was set for the civil war to come. The death toll was rapidly mounting. Western leaders called for Assad's resignation in August. But Assad was going nowhere. These were the days of the Arab Spring. People power and demonstrations were supposed to be enough to bring down the dictators. This happy narrative neglected to note a fact of salient importance. Deposed dictators – Zine El Abidine Bin-Ali in Tunisia, Hosni Mubarak in Egypt, Ali Abdullah Salah in Yemen – had fallen not only or mainly because of popular unrest against them. They were deposed because their patron, the United States of America, chose to abandon them in their hour of need. Assad had chosen different friends. He wasn't aligned with the West, but with Russia and the Islamic Republic of Iran. And the response of these two powers, from the very outset, was to provide the dictator with whatever level of support he required to stay in his seat.

The form this took varied. Russia used its Security Council veto at the UN to prevent any concerted action against the regime. Moscow also kept the weapons coming. The Iranians used their expertise in crowd control to help Assad control the demonstrations. By the end of 2011, it was clear that the bright lie of the "Arab Spring," according to which beautiful young people marching in the streets was all it took to topple dictators, wasn't going to work in Syria.

At this point, the opposition made the fateful decision to try a different way. Already, groups of recently deserted soldiers were arming themselves to defend the demonstrations against the attentions of Assad's soldiers. In early 2012, these began to crystallize into the first rebel battalions, organizing not only to defend protests, but also to attack the army and make areas in revolt impassable for the government's forces. The stage was set for war.

Lieutenant Bilal Khabir of the Free Syrian Army, with comrades, Sarmin, Idlib Province, Syria, February 2012.

I visited rebel-controlled Syria for the first time during that period. Idlib Province – one of the heartlands of the emergent insurgency. I remember the fevered atmosphere of the time and the hopes of swift victory. I interviewed a recent defector from Assad's airborne troops in a village called Sarmin close to Idlib City. Lieutenant Bilal Khabir was typical of the type of fighters who were capturing the world's attention at that time. Young, idealistic and brave, Khabir had deserted his unit after a brother officer was executed for refusing to fire on civilian demonstrators in Dera'a.

"I am with the law, not against the law," Khabir had told me, as we sat in a half-built structure that formed the rebels' headquarters in Sarmin. "The regime is fascist and criminal. We expect what happened in Homs to happen here. But even with our simple weapons, we are ready to fight. Either Bashar stays, or we stay. And freedom is the promise of God on earth."

They fought. Khabir himself rose to senior command in the rebellion in Idlib, before being terribly wounded in action in 2013. The rebels of Idlib and Aleppo and Dera'a, Quneitra and Raqqa, Homs and Hama and Deir al-Zor and Damascus made much of those areas no-go zones for Assad's army in the year that followed.

But even then, in those first days, it was possible to discern the sectarian hand inside the velvet glove of the rebellion's fine words. In Sarmin and Binnish, in February of 2012, Salafi fighting groups separate from the ragtag recent army deserters were already operating openly, apart from the enthusiastic, often younger rebels of the non-Islamist units. As the bloodletting continued in 2012 and 2013, it was these organizations that began to make headway. The secular rebels had no real vision or idea to put in their place. They just wanted to destroy Assad. The ideas came from the Islamists. The money, meanwhile, was coming mainly from Qatar and Turkey. Both these countries favored the emergent Islamist groups, whose inclinations mirrored their own.

And, of course, there was a discernible sectarian logic to the rebellion from the start. The Assad family hailed from the country's 12 percent Alawi minority. By no means were all those who had benefited from Assad's rule Alawis. There were Sunni Arabs and others in senior positions. Similarly, it was possible to find non-Sunnis and non-Arabs among the rebels. But the core dynamic was one in which the dictator relied, ultimately, on the support of his sect. The Shabiha, Alawi thugs and criminals, who would later be organized by the Iranians into a well-drilled militia, were crucial to the regime's survival from the start. Alawi-dominated military units – the special forces, the Republican Guard, the 4th Armored Division – were also relied upon from the outset when the large formations of Sunni conscripts were of doubtful loyalty.

The rebellion, similarly, emerged from the 60 percent Sunni-Arab majority of the country. In the course of 2012 and 2013, the sectarian logic of the war became increasingly inescapable. It was marked by the emergence of new and powerful formations that would play a crucial role. In the summer of 2012, Assad carried out a strategic withdrawal from a large swathe of Syria's northern border with Turkey. The withdrawal was itself dictated by sectarian logic. Assad was short of manpower. Because of his regime's narrow base, it had become clear that he did not have sufficient men to hold the entirety of a country largely in revolt against him. This fateful decision, made out of urgent necessity, began the process of fragmentation that is now very advanced in Syria. In the course of 2012 and 2013, the country effectively separated into a number of enclaves that survive to this day.

YPG fighters at a front line position in Ras al Ain (Sere Kaniyeh), Hasakeh Province, Syria, March 2013.

The regime held on to Damascus and the western coastal areas, and the road links between them. The Sunni rebels and Islamists had the east and south. The local franchise of the Kurdish PKK (Kurdish Workers Party), known as the PYD (Democratic Union Party), established itself as the de facto ruler of three non-contiguous Kurdish enclaves stretching along the Syrian-Turkish border. Their formidable Kurdish YPG militia emerged as one of the most powerful of the military organizations, which now divided control of the territory of Syria between them. The emergence of the Kurdish enclaves was further testimony to the sectarian dynamic now underlying the war.

The rise of extreme Salafi Islamist groups from the womb of the rebellion confirmed the trend. On January 23, 2012, the foundation of the Jabhat an-Nusra li-Ahl ash-Shām (Support Front for the People of the Levant) was announced. Usually shortened to Jabhat al-Nusra, this was the official franchise of the al-Qaida network in Syria. Led by Sheikh Muhammad al-Julani it quickly gained a reputation for military effectiveness and particular ruthlessness. Then, in May 2013, in the course of a dispute between the Nusra leadership and the leadership of the Iraqi franchise of al-Qaida, a faction began operating in Syria under the name of the Islamic State in Iraq and al-Sham (ISIS, or ISIL). Little noticed at the time, this jihadi group was set to transform the Syrian conflict, and then the region.

I entered Syria for reporting purposes on numerous occasions during that period. Amid the chaos and suffering, it was possible to discern that something extraordinary was taking place. The state structures that had existed since the early 20th century in this area – "Syria" and later "Iraq" were effectively ceasing to exist.

The author and a YPG fighter, at a position west of Kobani, March, 2014.

The old borders did not deter the military groups. Journalists crossed "illegally" with rebel assistance. Sometimes the crossings were lengthy and perilous affairs. But, more often, the border was hardly noticed, fictionalized. What had appeared at the beginning to be a war of a populace against a brutal dictatorship turned out to be something else entirely. The walls of the prison-house states of Syria and Iraq had been breached. New and unfamiliar entities were making war among the ruins.

In the Turkish border town of Kielis, in the early summer of 2014, I interviewed two ISIS members. I had just crossed back from Syria, after visiting the besieged Kurdish Kobani enclave.

At a place called Haj Ismail, a few days previously, comrades of the two men I met in Kielis had been shooting at me while I was interviewing a YPG commander at a forward position. The ISIS positions were about 200 meters away, across a flat, blank landscape. The firing began and I ran after the fighters as they raced for a machine-gun position behind some sandbags to return fire. It was a routine incident along a tense section of frontline. But it was passingly strange to be sitting in a room chatting and drinking tea with the men on the other side of the lines, just two days later.

The two men called themselves Abu Muhammad and Abu Nur. They were both Syrians. "If ISIS falls, you can forget about Sunni people in Syria," Abu Muhammad told me, after relating the story of his own long journey to the jihadi organization. The men were animated by a strange combination of local sectarianism and vast, millennial hostility to the West. The two fitted seamlessly together and the power of their combination was evident in the rapid growth of ISIS and the bloodthirsty fanaticism of its fighters.

As for the movement's goal, Abu Nur spoke about it with reverence. 'We want the caliphate, something old and new, from the time of Muhammad. The Europeans came here and created false borders. We want to break these borders." ISIS, in other words, was emerging directly from the reality of the Levant in 2014.

The situation, indeed, was becoming increasingly clear. As my friend Mahmoud, a onetime teacher turned political analyst and a supporter of the rebels bluntly expressed it, "In Syria, today, there are three groups worth mentioning. ISIS, the regime and the Kurds. Nothing else."

The reality of fragmentation and sectarian war burst across the borders a few months after that interview with the astonishing advance of ISIS into Iraq. By August, the jihadis had reached the gates of Baghdad and Erbil. They were stopped only after the entry of US air power into the fray.

The advance of ISIS into Iraq brought the logic of the Syrian war into the larger neighboring country. In the dramatic and terrifying events around Sinjar Mountain that summer ‒ the harrowing attempt at the genocide of the Yazidi people ‒the sheer savagery of the Sunni jihadis was laid bare. Here was a horror that defied description. But, while the singling out of the Yazidis carried with it a special evil, the Assad regime remained responsible for, by far, the largest number of the deaths in Syria.

The situation today retains the essential contours that emerged in mid-2014. The Syrian war has metastasized across borders. As a result, neither Syria, nor Iraq, nor indeed Lebanon any longer constitute states in the usually understood sense of that word. Rather, the entire vast landscape between the Iraq-Iran border and the Mediterranean Sea is, today, divided up between various political-military organizations and arrangements, almost exclusively organized along religious sectarian or ethnic lines.

They vary in orientation from the radical secularism and socialist outlook of the Syrian Kurds in autonomous "Rojava" to the murderous and apocalyptic Sunni jihadism of the Islamic State.

Along the way, one may find the Iran-oriented Shi'ite Islamism of Hezbollah and the Shi'ite militias of Iraq, the pro-Western, tribal conservatism of the Kurdish Regional Government in Iraq, and various types of Sunni Islamism in the poorly governed wastelands of the Syrian-Sunni rebels.

The war has, of course, also impacted far beyond the Middle East itself. The US and the West have staunchly sought to keep their involvement to a minimum. But, today, Western air power and special forces are playing a key role in the effort to reduce and destroy the Islamic State.

Further west, the Russian intervention after September 2015 almost certainly saved the Assad regime from destruction and reversed the course of the war. Currently, there are peace negotiations in Geneva and a fitfully observed cease-fire.

But the cease-fire relates only to the original war in Syria (regime vs. rebels). It doesn't impact on the other conflicts that emerged from its womb (YPG/SDF against ISIS, rebels against Kurds, KRG and Iraq against ISIS, Turks against PKK, regime against ISIS.

The bombings in Brussels on March 22 are the latest demonstration of the far reach of the war. What began with demonstrations by schoolchildren in Dera'a has now turned into a process of flux and convulsion of historic proportion.

A Yazidi refugee girl rescued from Sinjar Mountain, Newroz refugee camp, northern Syria, August 2014.

I think of the Syrian war, and my mind is filled once more with memories of astonishing vividness: The deep blue of the sky during a barrel bombing of the Sha'ar neighborhood in Aleppo, in the scorching summer of 2012. YPG fighters crossing the Tigris River in dinghies by night, in dead silence. The swishing of the water, the stars reflected in it and the blank expanse ahead. A hospital for Kurdish fighters in Derik, in summer 2014, filled with men wounded in the fight to open the corridor to Sinjar Mountain and the trapped Yazidis. Very dark-skinned Ktaeb Hezbollah militiamen at a frontline position just east of Ramadi city in Iraq in July 2015. The ghost-like figures of ISIS men, in black, running quickly past a gap in their defensive position. The first rebels, in Idlib Province, with hope, long since lost. The Yazidi refugees, just down from Sinjar, at the Newroz refugee camp in summer 2014, their exhausted, haunted eyes and the black horror of the things they described.

We are left with the bare facts behind all this – facts with which the policymaking echelon in the West has only just begun to grapple. The prison-house states are broken to pieces. The forces released from their ruins are swirling and clashing across the region and heading beyond it. Syria has become one of the hinges upon which regional and global events turn. The reputations of great powers, global and regional, are being made and broken among its ruins. It is war, and madness. And it is far from over.