A young Syrian turned up just over a week ago at a smart office block in Beirut with a terrifying message. Without giving his name, he said he wanted to speak to another Syrian who worked in the office, a well-educated man who left his country months ago. The visitor was taken upstairs and introduced himself. "I was sent to you by the shebab," he said – shebab might be translated as "the youth" or "the guys" and it meant he worked for the armed Syrian opposition – "and we need your help."

His story was as revealing as it was frightening. Damascus was about to be attacked. But the fighters were out of control. There were drug addicts among them. "Some of our people are on drugs," the visitor said. "They will take anyone out. We can't guarantee what some of these men will do. If they went into Malki [a mixed, middle-class area of central Damascus], we couldn't protect any of the people who live there. We are against the Salafists who are fighting – there are good Syrians, Druze and Ishmaeilis [Alawites] who are with us. But if we capture Damascus, we don't know how to run a small town, let alone a country."

It was a true civil war story. There were bad guys among the good guys and good guys among the bad. But sectarianism is biting into the Syrian revolution. At the end of last week, one Syrian told me that "they are bayoneting people in the villages around Damascus". Women, they say, have been raped outside the city of Homs – one estimate puts the number of victims as high as 200 – and the rapists are on both sides. The Syrian in Beirut knew all this and gave his visitor the following advice.

"Organise neighbourhood committees, well-dressed men who must be clearly identified and who must protect everyone, Christians, Druze, Sunnis, Alawites, everyone."

Five days later, the same Syrian received a phone call from an unidentified man in Damascus. "Boss, take your family out of Damascus. Give my phone number to your mum – she can call me if she has trouble on the way to the Lebanese border."

Up to 50,000 Syrians are believed to have fled into Lebanon last week. The man's mother was not among them; she could find no one to take her the 40 miles to safety.

The stories coming out of Syria now are of suspicion, chaos and death. President Bashar al-Assad's personal jet left Damascus on Wednesday night for the coastal town of Lattakia. Was Bashar fleeing his capital? No. It transpired the plane was carrying the body of his murdered brother-in-law, Assaf Shawkat, for burial near his native city of Tartous. In Lebanon, Sunni Muslims were already wildly celebrating his death. For it is Shawkat – his name actually appeared in a UN report that was later censored – who is widely believed to have planned and ordered the assassination of the former Lebanese prime minister Rafiq Hariri, whose convoy was bombed in Beirut on 14 February 2005. Hariri, a Sunni, had fallen out with Assad over Syria's role in Lebanon. Shawkat was the hatchet-man. Now the bomber had been bombed to death himself.

Two months ago, it is said in Damascus, there was an attempt to poison Shawkat and the two other men who were assassinated with him last week, General Daoud Rajha, the Christian defence minister, and the Sunni general, Hassan Turkmani, head of Assad's "crisis cell". But the cook put 15 poison tablets into their food rather than the prescribed five – such was his enthusiasm – and the men could taste the food was bad. The cook escaped. This is the most accurate of several "poisoning" stories, but there is no reason to disbelieve it. There is nothing new in treachery in the regime. Bashar's uncle Rifaat – now residing in Mayfair – twice tried to stage a military coup against Bashar's father, Hafez.

Bashar Assad received some advice last month from a Syrian with whom he is acquainted: if he ended his strikes against civilians, the Europeans would be content to let him remain in power for at least two more years – because the west wanted direct oil pipelines from Qatar and Saudi Arabia via Jordan and Syria to the Mediterranean in order to end Russia's stranglehold on Europe's gas and oil. Assad's reply came in his last speech. "There are people with patriotic intentions," he said. "But they don't know the nature of the conflict." All the evidence suggests that it is Assad himself who has not grasped the "nature" of this conflict.

Two of his relatives, however, do apparently understand it. Mohamed Makhlouf, the president's uncle on his mother's side, and his son Rami, Assad's first cousin, have been seeking a deal with the French government to allow them to live in exile in Paris if the regime collapses. The Makhloufs have been at the centre of the government's corruption in Syria and they are one of the reasons for the revolt and its 17,000 fatalities. For despite the dictatorship and its secret police apparatus, corruption was the glue that held the regime together.

Northern Syria, for example, has always been a vast smuggling zone, a place where every man in almost every family owned a rifle – this was one reason why the Assads always appointed tough former military men as provincial governors in the Aleppo region – and goods flowed from Turkey through Syria to Jordan and the Gulf. But once Syria's economy began to slide, the mutual corruption of state and banditry, and between a minority Alawite-led regime and its favourites in the Christian and majority Sunni communities, meant that the glue began to melt.

If this initially took the form of unarmed demonstrations across the country – provoked by the torture and murder of a 13-year-old boy by secret policemen in Deraa in March last year – armed men did appear rapidly on the streets of some towns. There is video footage of gunmen on the streets of Deraa that same month and al-Jazeera footage of armed men fighting Syrian troops just across the northern border of Lebanon in April 2011. Mysteriously, al-Jazeera chose not to broadcast it.

Now, of course, Saudi Arabia and Qatar, where al-Jazeera is based, make no secret of the funds and weapons they are running into Turkey and Lebanon for the resistance – without apparently caring very much who the "resisters" are. The Lebanese army managed to stop one out of five shiploads of guns, but the others, carried on Sierra Leone-registered vessels, were able to unload.

One of the two organisations that claimed responsibility for last week's Damascus bombing, Liwa Islam – the Islam Brigade – raises again the Salafist element in Syria's armed opposition. One newly arrived refugee from Syria told me last week that they have forbidden alcohol and openly say they intend to die fighting in Damascus. Given the savage response of the Syrian regime, they may get their last wish.

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