REUTERS/Molhem Barakat A fighter from Islamist Syrian rebel group Jabhat al-Nusra inspects a resident's identification papers at a checkpoint in Aleppo's Bustan al-Qasr, October 26, 2013. 
Now that the uprising has succeeded in his home town near Aleppo, pro-democracy activists are living in fear again - and this time those who brand them "traitor" don't bother to knock.
Two years ago, after Abdullah broke off his studies to run social media campaigns against Assad, he was held and tortured by security men. This summer, it happened again - only now it was Islamist gunmen loyal to al Qaeda who smashed into his family's house, broke everything in their way and took him off to a cell where, once more, he was blindfolded and beaten.
"The sad thing is that those who were doing this were not Assad's police," Abdullah told Reuters from Turkey, where he managed to flee after his latest ordeal. "They were fighters who were supposed to be fighting for freedom, our freedom.
"Back then they called me 'traitor' for demanding freedom. These armed men also tortured me for calling for freedom."
His story is increasingly familiar across northern
Abdullah's experience also highlights the fragmentation of Syria's opposition, which greatly complicates new international efforts to end a civil war that has killed over 100,000.
Reuters spoke to 19 Syrians who describe themselves as activists for democracy. All gave similar accounts of violence and intimidation by militant Islamists in northern areas no longer controlled by Assad's "mukhabarat" security services.
Most were students when Syria's Arab Spring protests began in March 2011. All got involved in publicizing demonstrations - and documenting Assad's crackdown on them - using social media. They went on, as self-taught journalists, to provide images and reports for Syrians and international media as the war spread.
Some, like Abdullah, have now had to flee for their lives.
They, and those still inside Syria, say Islamist militants have begun a campaign to silence them and free speech in general. Last month, two media activists were shot dead in broad daylight in Aleppo, Syria's biggest city. Some have been seized and are being held. Others have simply disappeared.
AL QAEDA FEAR
In particular, those who spoke recounted the fear spread by the Islamic State of Iraq and the Levant (ISIL). The al Qaeda-linked group, dominated by foreigners blooded in other wars, from Libya to Iraq and Afghanistan, does not tolerate critics.
"It is impossible for me to go to Syria now. I am wanted by the regime and by al Qaeda," said Rami Jarrah, who ran a radio station in the city of Raqqa until early October, when ISIL gunmen shut it down and took away one of his colleagues.
Now living in Turkey, from where Radio ANA continues to broadcast into Syria, Jarrah won early fame among "media activists" in 2011, employing the English of his British education to forge an international reputation blogging from Damascus, where foreign news organizations had little access.
When a pen-name - "Alexander Page" - failed to shield his identity, he fled the country but returned later to "liberated" northern Syria, where he helped set up broadcasting in Raqqa.
The station's mistake, he said, was to open its airwaves to phone-in callers venting grievances against the Islamists:
"People were calling in and saying ISIL did this and did that. 'They closed my shop' or 'attacked my wife and forced the hijab on her'," Jarrah said. The militants, online themselves, accused him of "atheism" and put a price on his head.
Journalists have long faced suspicion and harassment from rebels, gunmen forcing them to stop filming, sometimes seizing equipment or raiding apartments and cafes where they have set up "media centers" to share and distribute videos and reports.
But in recent months, events have taken a more sinister turn. Several of those working in Aleppo have gone missing. In some cases, their bodies have been found - tortured, shot and left on the street. Friends and relatives of others have been told by militants that the activists have been arrested.
Hazem Dakel, from Idlib, described what that could mean.
Now also living in Turkey, his ordeal began when two men on a motorbike forced his car to a halt after he had been filming in an area run by ISIL. Held in a house, they accused him of "opposing Islam". He was lucky, and escaped through a window.
If he had any doubt what would have happened had he stayed, a call from one of his captors to an acquaintance still in Syria has since removed it: "They were planning to execute me on the night I escaped," Dakel said. "They were going to take me to a notorious abandoned factory where they execute people."
UNDER SURVEILLANCE
The militant Islamists have won respect among Syrians in the north, partly by their fighting mettle, party by imposing order where feuding among rival rebel warlords had broken out, partly by ensuring supplies of food and medicines. But for democratic activists, that does not excuse other failings.
"Our problem with them is ideological," said Jarrah. "They want to force their ideology without asking our opinion.
"The regime deprived us of freedom of expression and they are doing the same," he added. "Anyone liberal - or not Islamic enough according to their standards - is getting arrested. They want all local radios to broadcast from a centre they control."
Jarrah said he knows of at least 60 activists who have been detained by al Qaeda gunmen or have simply gone missing.
One man still living in rebel-controlled territory near the central city of Hama described the fear that still forces him to conceal his identity - as he did when Assad held the area.
"I live in a liberated country area near Hama and I walk around looking over my shoulder all the time," he said. "It is like we are back to the old days when we were running from the mukhabarat. But now we are running from our Islamist brothers."
Though he himself favors an Islamic state, the activist said that his online condemnations of sectarian killings of civilians who belonged to Assad's Alawite minority prompted warnings from Islamist militants that he should keep quiet.
Like the government's security service, Islamist groups keep a close eye on what activists are saying on the Web.
"They know everything," an activist from Deir al-Zor said. "One word can get you killed or make you disappear ... They look for our names, what we said to this newspaper or to that magazine. They watch us like hawks. And then they act."
Rami Jarrah and others were publicly condemned in an online post under the headline: "Western agents in Raqqa, or democracy activists? In religious terms, is there much difference?"
In the middle of a civil war that shows little sign of abating despite international plans for a peace conference in January, Syrians have limited means to oppose the armed groups.
Jarrah said those who campaigned for free speech must bear some blame for their predicament: "We used to say 'It's OK, they believe in God and fight on the frontlines'," he said.
"So we ignored their atrocities."
Abdullah, the activist who fled Aleppo province, argued that the experience of standing up to the Assad family after four decades of submission would mean Syrians may more quickly break the new "barrier of fear" to speak up against al Qaeda.
There have been signs of anti-Islamist demonstrations.
Some people filmed themselves marching this month outside a building in Aleppo where they believed ISIL was holding fellow activists. A video on YouTube shows about 30 of them chanting: "Shame! Shame! Kidnapped in free, rebel territory!"
But, just as Assad accuses his opponents of playing stooges to foreign powers, militant Islamists in Syria say they will not heed complaints from activists they also view as traitors.
One Syrian blogger who is close to another al Qaeda-linked group, al-Nusra Front, dismissed accounts of oppression and intimidation from democratic activists as exaggerated and intended to "please the West" by slandering Islamists.
"Those who accuse Islamists of violations," he said, "Are following a Western agenda."
(Editing by Alastair Macdonald)