REYHANLI, Turkey -- Gen. Ahmed al Berri, the top officer of the Western-backed Syrian rebels in Hama province, was driving up Syrias main north-south highway in mid-December when he slowed at a checkpoint, expecting a friendly wave-through by the radical Islamists who were manning it.
The fighters of the Islamic State of Iraq and Syria, most of them non-Syrians, had something else in mind, however.
They wanted the car, and I refused to give it, he recounted to McClatchy. They showed their weapons, and we showed ours. But there were 30 of them and only four of us, so he agreed to go with his two bodyguards and a second officer for what the Islamists said would be an appearance before a Shariah court judge.
Instead, Berri and his companions were arrested, blindfolded and bound.
For the next 18 days, Berri said, he was held in a makeshift prison inside a house in the village of Killi, about five miles south of the Turkish border. For Berri, it was a surprising introduction to a radical group that in the space of a few months had come to dominate much of northern and eastern Syria, lording it over more moderate rebels and installing a reign of terror the extent of which is only now becoming clear.
They were professionals, Berri said of the men who regularly interrogated him in two-hour sessions. Each of his questioners two were Syrians and the others were from Egypt and Tunisia focused on a different topic. One would ask when he defected from the Syrian army, a second would ask what weapons hed brought with him and a third questioned him about his contacts. They grilled him about his relationships with Americans, Turks, Qataris and Saudis all countries that have provided aid to rebel groups.
Their aim was to know what the rebels were doing, what weapons they are using, how theyre distributing forces, who theyre in contact with outside the country and what their goals are, Berri said. And they sought to identify fighters in his militia, the sort of information that an ostensible ally could obtain by much simpler means.
It was like Syrian intelligence, he said, concentrating on minor details. He added, It indicates they know their business very well.
Berri said the entire compound in Killi appeared to have been organized around the prison and interrogation process, rather than war-fighting. He estimated that at least 100 armed personnel were deployed to run and guard it, including his team of professional interrogators.
How the Islamic State of Iraq and Syria became a dominant force in Syrias rebellion against the government of President Bashar Assad in just a few months after it announced its formation last April is a mystery. It was considered an ally by most other rebels until well into the summer; the U.S.-backed Free Syrian Army even praised its role in the August capture of the Mannagh air base north of Aleppo, which other rebel groups had been besieging for more than a year, unsuccessfully, until two ISIS suicide bombers blew themselves up and destroyed the bases command center.
But its enmity toward much of the rebel movement had been growing. In July, it kidnapped the leader of a rival rebel group in Raqqa, who hasnt been seen since. In August, it bombed that groups Raqqa headquarters, killing many of its commanders. In September, it seized the town of Azaz from the Free Syrian Army, and it took control of several major crossing points along the border with Turkey, cutting other rebels from their supply routes.
The consequences for Syrias opposition movement could be many, and severe: As extemists have co-opted the revolution, the U.S. and other countries have hesitated to help or have even suspended aid to Syrias rebels, fearing the spread of radical Islam.
Last month, moderate and Islamist rebel militias combined forces to attack ISIS throughout northern Syria, forcing it to abandon Killi and roughly half its bases, and releasing hundreds from ISIS jails. But ISIS remains the dominant rebel force in Raqqa province and in much of eastern Syria, where it controls the countrys oil fields and its transit routes to Iraq, where ISIS traces its origin.
ISISs stated aim is to restore a medieval Islamic caliphate in the area now occupied by Syria and Iraq. But moderate Syrian activists wonder now whether it doesnt serve some other purpose. They note that its primary mode of reaching its goal has been through the abduction primarily of Assad opponents, the torture and interrogation of its detainees and massive theft. Rebel leaders dont hesitate to link ISIS to the Assad regime, though the evidence they cite is largely circumstantial. Its claim to al Qaida lineage has been rejected by that groups head, Ayman al Zawahiri, who last week pronounced that not only had al Qaida opposed ISISs move into Syria, but al Qaida also hadnt been consulted on it.
On the eve of last months uprising, the newly elected overall rebel commander, Jamal Maarouf, said his forces were attacking ISIS because it behaves like the Assad regime, according to an interview in Syrias Second Front, a documentary to be shown Tuesday on the PBS news program Frontline.
At its peak, a McClatchy investigation shows, ISIS had at least 60 bases in northern Syria. Opposition activists say that almost every one of them had a prison. About half of those remain under ISIS control.
Interviews with others whove been freed from ISIS prisons show the extent to which the group mixed professionalism with terrorism and torture.
Bunyamin Aygun, a Turkish photojournalist who was held for 40 days, said he was questioned for 17 days at Killi by interrogators who took precautions in verifying his statements that he was journalist. They were very professional in the way they did background checks, he told McClatchy.
They asked him for the dates of his photographs, rather than looking him up under his name, fearing that Turkish authorities would track down a routine Web search for him coming from Syria. And they took his credit card and PIN number to a bank in Reyhanli, inside Turkey on the border, to search his bank account and see whether his earnings were that of a journalist and not a spy.
What wasnt so professional was the supposed court that decided his case. I was never actually put on trial, he said. They just told me my case was going before the qaid (judge) and he would decide. One day later he was told hed been sentenced to death by beheading. His captors told him he should repent and read the Quran, and his execution would take place the next day.
At that point, Turkish news outlets began to write about his disappearance. His jailers told him that he was more important than we thought and decided not to kill him. Aygun was rescued when rebel forces seized Killi on Jan. 5.
Other prisoners told similar tales that rebel authorities memorialized in statements McClatchy reviewed. They reveal not only torture and abuse, but also an ISIS fixation on property and cash that provides insight into the groups finances. Well-informed humanitarian aid officials say ISIS relied in part on ransoms paid by foreign news organizations and aid organizations for the release of kidnapped workers. Expropriation of private property appears to be another method.
Rae Shaabo an Naser, a 35-year-old taxi driver from Sarmande, near the city of Idlib, told his rescuers that hed been beaten, tied to the ceiling and doused with water and forced to sit naked out of doors. Throughout it all, his interrogators asked him about the property of his brother, whod emigrated to Hungary. They asked me to give them the keys to his farmhouse, he said in his statement.
That, too, was a theme in another of ISISs prisons, this one at the former eye hospital in Aleppo, Syrias largest city, where ISIS became a force in August.
Khalid A., 25, a media activist whos worked for the anti-Assad opposition and who asked not to be identified by his full name because of security concerns, said he was held there after he was stopped in mid-August by a black four-wheel-drive car that blocked the road. Masked gunmen seized him and took him to the recently captured Mannagh air base. On the way into a building four men beat him with cables, and after he was taken to his room, a non-Syrian, possibly an Iraqi, interrogated him about his job and his contacts.
The beatings after his transfer to the eye hospital were worse, he said. For most of his 34 days there, he was held in a makeshift underground dungeon with 10 other people. For five days, he had no food at all and later only a half-pound of bread a day. He lost 66 pounds in prison.
People were in a tragic state, he told McClatchy of the others in his cell. One had bones broken. Another couldnt walk. Another couldnt use his hands, after being hanged from the ceiling for 22 days. And there was Abu Tony, an elderly Christian whod been held for 60 days, and was given no medicine for his diabetes.
Everyone was there for a reason. There were no random abductions, he said. Everyone had been captured by name, many of them arrested at their houses. Abu Tony was accused of converting to Islam and then trying to re-convert to Christianity, charges Khalid said were almost certainly specious. The real reason for holding him, Khalid suspected, was that he owned a metalworking factory in Aleppo that ISIS wanted to expropriate.
There were two brothers, aged 25 and 28, who owned a flour mill and farm near the air base. Khalid said they told him theyd donated weapons to the Free Syrian Army to help in the siege of the base but that ISIS had accused them of supporting Assads military.
But the real reason they were arrested, Khalid said, was probably their wealth. The brothers said ISIS had taken their cars, 200,000 euros - about $270,000 - and more than 37 pounds of gold, worth about $750,000 at todays prices.
One day, Khalid said, the guards removed them from the room, and they never returned.
Many of the guards and interrogators, Khalid said, had been on death row at Abu Ghraib, the Iraqi maximum-security prison west of Baghdad, and had escaped during an al Qaida-organized breakout in mid-July. Other guards were volunteers from Tunisia, Afghanistan, France, Denmark and Chechnya. One of the Iraqis concealed a tattoo forbidden in Islam beneath his shirtsleeve. The Chechen escorted prisoners for their once-daily excursion to the toilet. He only had two words of Arabic, Khalid said.
Khalids first interrogation in Aleppo occurred seven days after his abduction. The investigation room smelled of diesel fuel, and he could smell blood on the floor. Hooded, he couldnt see who was attaching electrodes to his back and neck. They tied my hands behind my back, sat me on the ground and asked me how I was, he recalled. Then they turned on the power. No one said anything. They just used electricity for 40-50 minutes. They paused for about a minute between jolts; the longest, he said, lasted about 10 seconds.
At the end, I couldnt see or hear anything for 10 minutes. My system was completely confused. I couldnt stand up.
His captors then hanged him by the handcuffs in what is called a ghost torture. He dislocated his shoulder and was later diagnosed as having a herniated disk. After another hour, two men with electrical cables beat him he calculated 400 to 500 times. My body was purple from the pelvis to the neck, he recalled. I was shouting and yelling. I dont remember what I said. I remember the pain. He lost consciousness. I couldnt handle the pain.
He showed a reporter large welts on his upper left back, where he said the electrode had been attached.
On the second day, his captors brought him in for interrogation about opposition forces, the Free Syrian Army, his job, his bosses and his co-workers.
Finally, a man described as a judge came in. You must be killed, Khalid recalled him saying. Do you prefer a rope or a knife? Khalid said he replied, Maybe a bullet in the head would be better. The judge responded that hed decided to slaughter him with a knife. One of the guards came, grabbed Khalid by the hair and put a knife to his throat.
Get ready to face your God, the judge said. I said, Im ready. I dont want to face another interrogation, he said. I felt the angel of death pass in front of me, Khalid told McClatchy.
But the knife stroke never came. Ten days later he was released.
Hundreds of prisoners werent so lucky. The Frontline special includes video of masked gunmen executing seven Free Syrian Army soldiers in al Atarib in late November, shooting them in the back of the head.
In a Dec. 19 report, Amnesty International quotes detainees who reported on two ISIS executions in or near Raqqa in eastern Syria in mid-October. Four members of other armed militias were condemned to death after purported trials. Take him away for retribution. Let his head fly, the prisoner quoted the unnamed emir as decreeing for each of the four. That night, guards called out the names of the prisoners and they were taken away, never to reappear. Three others were sentenced to death for alleged adultery.
As described by freed detainees, ISIS devoted enormous resources to find, seize, hold and interrogate its prisoners. But even as it set up a state within a state, the Assad regime left ISIS untouched.
Khalid recalled that in the 34 days he was held in Aleppo, the regime never attacked the ISIS base. But the base of Liwa al Tawhid, an Islamist militia, just 50 yards away, was bombed many times.
Berri recalled that during his time at the house in Killi, Syrian government forces never attacked the camp.
Berri eventually was released, thanks to influential friends. A brigade of Hama fighters mounted a siege of an ISIS base near Saraqeb and threatened to attack it if anything happened to him. And a delegation of Islamic clerics went to the Shariah court in Ad Dana, the ISIS headquarters, and warned that 10,000 militants were ready to attack if anything happened to Berri, he said. To prevent him from being abducted, the clerics arrived Dec. 23 in a convoy of seven vehicles, mounted with heavy machine guns. It still took eight days before he was freed.
Even then, Berris captors refused to release the second officer and the bodyguards. So Berri returned to the prison until the judge whod ordered his release freed them.
When Berri left, they kept his car and his personal effects: my wallet, my money, my ring, everything.
Five days later, Syrian rebels stormed the Killi camp and freed it.
This story is part of a collaboration between McClatchy and Frontline, whose documentary Syrias Second Front will air Tuesday, Feb. 11. Check your local listings for the time. You can also join a live Web chat below on Wednesday at 1 p.m. ET with FRONTLINE correspondent Muhammad Ali and McClatchy's Roy Gutman.