It was 5am, and Mohamad Baree was hiding with his fighters behind a large rock. Some 300 metres away, a column of Syrian army tanks was advancing towards Aleppo through the countryside. The group of rebels were waiting for it. Baree watched. He then set off a powerful roadside bomb. It blew two of the tanks up. The others staged a panicky retreat to their base in the northern city of Idlib.

"From a military point of view the operation was successful," Baree tells me a week later, as we bump along in the back of his unit's battle-scarred minivan. Baree, 27, is dressed in khaki fatigues. He carries a Kalashnikov and a pistol. Despite his appearance, he explains that he is actually a pharmacist who has spent seven years living in Odessa; his brother, another fighter in Syria's revolution, a lawyer.

Syria's grinding 17-month war has typically been portrayed as a sectarian conflict. In this version, Bashar al-Assad's embattled Shia Alawite sect – about 10% of the population – is pitted against the country's Sunni majority. To an extent, this is true. But the reality is more complex. Some of Baree's co-fighters are members of what could loosely be called the rustic poor – carpenters, decorators, farmers. Others are educated. Baree says that a professor of chemistry has been giving the rebels tips on bomb-making, helping their military effectiveness. There are army defectors, medics, video activists, even information officers.

The sectarian faultlines are blurred as well. Baree acknowledges that his own group of around 150 rebels, from the village of Korkanaya, near Idlib, is predominantly Sunni. But he says many of his friends are Alawite. "We talk over the internet. They don't like what Bashar is doing either," he says. Baree says he has broken off with one childhood friend, a Sunni and a local teacher; the teacher had implacably supported the regime ever since Syria's uprising began in spring 2011.

The situation in Aleppo, Syria's largest metropolis, engulfed by fighting since July, meanwhile, is also many-layered. Aleppo is one of the most ancient cities on the planet, home to various Christian denominations, historically a large Jewish population, now all fled, as well as wealthy Sunni traders, many favourably disposed to the regime.

In the mountains just outside Aleppo you find the ghostly ruins of Byzantine churches. There are poor Kurdish hamlets. I find the frontline town of Anadan semi-wrecked and abandoned.

One Aleppo resident I speak to, an engineer living in a regime-controlled district, says he supports the revolution. But he admits many of his neighbours don't. "If I were to generalise I would say the middle class and upper class don't want the rebels. They want everything to be how it was," he says. Many poorer Aleppines had welcomed the rebel Free Syrian Army (FSA); others viewed it as a bunch of dangerous extremists; almost all were terrified of what the fighting would bring.

According to Baree, Syria's revolution has little to do with external forces, or Islamist radicalism. It is, he tells me, the product of Syria's own domestic dynamic and a logical reaction to the brutal behaviour of Assad. Assad had responded to the Arab spring and demands for political reform by arresting, torturing, and shelling his opponents, thus turning a few isolated demonstrations into a mass armed insurrection. "We tried to persuade him through peaceful means. But this didn't work. So we took up weapons," Baree says. Some guns from outside were arriving in Syria. But none have reached his unit, he adds.

Our conversation takes place as we drive through Syria's FSA-controlled north, a rustic mini-empire of villages, silver olive groves and boys herding sheep. Even here, the regime is never that far away. At one point we pass within a kilometre of a government checkpoint – a yellow water tower near the Bab el Hawa border with Turkey. Our driver Mohammad puts his foot down and races through an exposed patch of farmland. "He nearly crashed and killed us yesterday," Baree says of Mohammad, one of many Sunni defectors from the Syrian army.

Just over the border, I meet Thaer Abboud, an opposition activist who fled to Turkey from Syria last year. Abboud is an Alawite from the Mediterranean coastal town of Latakia. Some observers have suggested that Latakia and its surrounding mountain villages could form an Alawite heartland, with the regime and army retreating from Damascus and setting up their own an impregnable mini-state there. Abboud, however, says that far from being a loyalist Alawite fiefdom Latakia is split. Some 50% of the town oppose Assad, including some Alawis, a number of whom have been persecuted: "It isn't a matter of Alawis versus Sunnis. It's a political thing. In Syria we don't have separate communities. There are marriages, relationships between Sunnis and Alawis. We've lived together for 1,000 years. We're not dependent on religion."

Abboud agrees that Assad has played the sectarian card, telling Syria's Alawites that without him they were finished, and evoking historical memories of Alawite oppression by both the Ottomans and the French. "Assad's message is: 'If the regime stays you live. If we go you will be killed.'" In reality, Abboud tells me, all parts of Syria have been ground down, by the regime's callousness and feudal arrogance.

Three years ago the government even forbade locals in Latakia to swim in the sea. "People can't take it any more. Everyone was just waiting for a spark," he says.

And what of the attack on the tank column? It may have been a military success, but it had tragic consequences. One of the tank drivers who survived the ambush fired a shell into a residential building. It hit a fifth-storey flat on Idlib's 30th street. Five members of a family were sleeping there. All were killed, the latest victims in Syria's unrelenting war.