Ammon News - ALEPPO (Reuters) - As the Syrian civil war got under way, a former electrician who calls himself Sheikh Omar built up a brigade of rebel fighters. In two years of struggle against President Bashar al-Assad, they came to number 2,000 men, he said, here in the northern city of Aleppo. Then, virtually overnight, they collapsed.

Omar's group, Ghurabaa al-Sham, wasn't defeated by the government. It was dismantled by a rival band of revolutionaries - hardline Islamists.

The Islamists moved against them at the beginning of May. After three days of sporadic clashes Omar's more moderate fighters, accused by the Islamists of looting, caved in and dispersed, according to local residents. Omar said the end came swiftly.

The Islamists confiscated the brigade's weapons, ammunition and cars, Omar said. "They considered this war loot. Maybe they think we are competitors," he said. "We have no idea about their goals. What we have built in two years disappeared in a single day."

The group was effectively marginalized in the struggle to overthrow Syria's President Bashar al-Assad. Around 100 fighters are all that remain of his force, Omar said.

It's a pattern repeated elsewhere in the country. During a 10-day journey through rebel-held territory in Syria, Reuters journalists found that radical Islamist units are sidelining more moderate groups that do not share the Islamists' goal of establishing a supreme religious leadership in the country.

The moderates, often underfunded, fragmented and chaotic, appear no match for Islamist units, which include fighters from organizations designated "terrorist" by the United States.

The Islamist ascendancy has amplified the sectarian nature of the war between Sunni Muslim rebels and the Shi'ite supporters of Assad. It also presents a barrier to the original democratic aims of the revolt and calls into question whether the United States, which announced practical support for the rebels last week, can ensure supplies of weapons go only to groups friendly to the West.

World powers fear weapons could reach hardline Islamist groups that wish to an Islamic mini-state within a crescent of rebel-held territory from the Mediterranean in the west to the desert border with Iraq.

That prospect is also alarming for many in Syria, from minority Christians, Alawites and Shi'ites to tolerant Sunni Muslims, who are concerned that this alliance would try to impose Taliban-style rule.

REPROBATES AND OUTLAWS

Syria's war began with peaceful protests against Assad in March 2011 and turned into an armed rebellion a few months later following a deadly crackdown. Most of the rebel groups in Syria were formed locally and have little coordination with others. The country is dotted with bands made up of army defectors, farmers, engineers and even former criminals.

Many pledge allegiance to the notion of a unified Free Syrian Army (FSA). But on the ground there is little evidence to suggest the FSA actually exists as a body at all.

Sheikh Omar told the story of his brigade while sitting in a cramped room at his headquarters, a small one-storey building surrounded by olive tree fields in Aleppo province. Wrapped around his chest he wore a leather bandolier that held two pistols, grips pointing outwards, ready to be drawn by crossing his arms.

He said he was from a poor background in rural Aleppo province. When he and a handful of others had started a rebel group to oppose Assad, fear had made it hard to recruit. The rich and law-abiding were scared. Only outlaws and reprobates would join him at first.

"We were looking for good people. But who was willing to work for me and help me? Those who used to go to bars, to fight with people and steal. Those are the people who allied with me and fought against the regime." As he spoke some of his remaining fighters tried to interject; he silenced them, saying he wanted to be honest.

LOOTING

Ghurabaa al-Sham started with modest aims, Omar said. They would enter small police stations and negotiate a handover of weapons in return for free passage out of the area for the police.

But their numbers grew to 2,000 men, he said, and they fought battles to take border posts with Turkey and were one of the first rebel brigades to move into Aleppo, Syria's most populous city with 2.5 million inhabitants.

More than half of the city fell to the rebels, but Assad's army pushed back, fighting street by street for months. A stalemate ensued. Very little progress has been made from either side for almost a year.

Where the government forces did cede ground, Aleppo's residents did not welcome the rebels with open arms. Most fighters were poor rural people from the countryside and the residents of Aleppo say they stole. Omar acknowledged this happened.

"Our members in Aleppo were stealing openly. Others stole everything and were taking Syria's goods to sell outside the country. I was against any bad action committed by Ghurabaa al-Sham. However, things happened and opinion turned against us," he said as his men squirmed in their seats, uncomfortable with his words.

Ghurabaa al-Sham was not the only group to take the law into its own hands. In Salqin, a town in Idlib province bordering Turkey, fighters from a rebel brigade called the Falcons of Salqin have set up checkpoints at the entrances to the town.

Abu Naim Jamjoom, deputy commander of the brigade, said the rebels take a cut of any produce - food, fuel or other merchandise - that enters Salqin. The goods are distributed to the town's residents, he said, but some rebel groups steal this "tax" for themselves.

Part of the problem is that the rebel groups are poorly equipped and badly coordinated. Jamjoom said he had 45 men with guns and two homemade mortar launchers but was desperately low on ammunition. "Everything we have has been looted from the regime," he said, echoing the response of most rebel commanders when asked if they have received any outside support.

Jamjoom, who wore a blue camouflaged outfit and kept a grenade in his left pocket, said he had registered his group with the Supreme Military Council, a body set up by the U.S.-backed Syrian National Coalition of opposition groups to help coordinate rebel units.

"We haven't received any help from the military council," Jamjoom said, drinking sweet tea on the balcony of his headquarters, the house of a pro-Assad dignitary who had fled the area. "We have to depend on ourselves. I am my own mother, you could say."

He tugged at his uniform. "I bought this myself, with my money," he said. He also said his group buys weapons from other brigades, "from those who have extra." Weapons trading by rebel groups raises the risk that arms supplied by Western powers may fall into the hands of Islamist groups.

Western officials say military aid will be channeled through the Supreme Military Council. A Western security source told Reuters the council is trying to gain credibility, but as yet it has little or no authority.

Meanwhile, Jamjoom and his men were largely staying around Salqin, low on ammunition and low on energy. Inside the mansion they have commandeered, rebels lazed about on the gaudy fake-gold furniture in a room full of books, including religious texts and a copy of "The Oxford Companion to English Literature."

ISLAMIST ARBITERS

The Islamists are more energetic and better organized. The main two hardline groups to emerge in Syria are Ahrar al-Sham and Jabhat al-Nusra, an al Qaeda offshoot that has claimed responsibility for dozens of suicide bombings, including several in Damascus in which civilians were killed.

But Islamist fighters, dressed in black cotton with long Sunni-style beards, have developed a reputation for being principled. Dozens of residents living in areas of rebel-held territory across northern Syria told Reuters the same thing, whether they agreed with the politics of Jabhat al-Nusra or not: the Islamists do not steal.

Aaron Zelin, a fellow at the Washington Institute for Near East Policy who researches Islamic militants, said the main reason groups such as Jabhat al-Nusra and Ahrar al-Sham have become popular is because of the social provisions they supply. "They are fair arbiters and not corrupt."

In Aleppo four Islamist brigades, including Jabhat al-Nusra and Ahrar al-Sham, have taken over the role of government and are providing civilians with day-to-day necessities. They have also created a court based on Islamic religious laws, or sharia.

The Aleppans call it "the Authority" and it governs anything from crimes of murder and rape to business disputes and distributing bread and water around the city. The power of such courts is growing, Authority members and rebels said, and is enforced by a body called the "Revolutionary Military Police."

At the police's headquarters, a five-storey building surrounded with sandbags, a large placard outside read: "Syrian Islamic Liberation Front." It referred to a of several Islamist brigades, forged in October 2012, which seeks to bring together disparate fighting groups. Its Islamist emphasis has already alienated some other fighters.

The head of the Aleppo branch of the Revolutionary Military Police, Abu Ahmed Rahman, comes from Liwa al-Tawhid, the largest rebel force in Aleppo. Ostensibly al-Tawhid has pledged its support for the U.S.-recognized Syrian National Coalition, but its role in the Authority alongside Ahrar al-Sham and Jabhat al-Nusra shows an alliance with more radical groups.

As Rahman sat at a large desk on the ground floor, people rushed in and out, asking him to stamp and sign documents. He said that the worst problem the police had encountered so far was with Ghurabaa al-Sham, who had clashed with a sub-division of Liwa al-Tahwid for control of Aleppo's industrial city, a complex of factories and office blocks sprawling over 4,000 hectares on the north-east outskirts of the city.

"Ghurabaa al-Sham fighters were annoying people, looting," he said. The industrial area offered plenty of plunder. Residents of Aleppo said rebels found machinery and equipment in the factories that could be sold in Turkey.

Rahman said the Authority summoned Ghurabaa al-Sham to a hearing but they didn't up. "Then all the brigades went to get them. Jabhat al-Nusra, Ahrar al-Sham and other rebel units," he said.

Abu Baraa, an employee at the Authority, said: "We gathered a lot of people with guns and everything. We went to the industrial city and we arrested everyone who was there. Then we did the interrogation. Those who did not steal were set free, and the others were put in prison.

"Before this Sharia Authority, every brigade did whatever it wanted. Now they have to ask for everything. We are in charge now, God willing. We are the supervisors. If you do something wrong, you will be punished."

A POWER STRUGGLE

Members of Ghurabaa al-Sham gave a different version of events and have a different world view. "Why is the Sharia Authority allowed to control us? We didn't elect them," said Abdul-Fatah al-Sakhouri, who works in the media center for Ghurabaa al-Sham, an old taxi station in Aleppo where he and some other fighters upload videos of battles against the Syrian army onto YouTube.

Al-Sakhouri, previously a mathematics teacher, said the head of the Ghurabaa al-Sham unit in the industrial city had gone to the Authority to sort out the dispute. "Commander Hassan Jazera was there for three hours and then left. It shows that they didn't arrest him and there were no real charges against us," he said.

The dispute, Ghurabaa al-Sham fighters said, was really about power. They said their brigade, made up of fighters ranging from Islamists to secularists but all in favor of a civilian state, was not part of the Islamist alliance formed between Jabhat al-Nusra, Ahrar al-Sham and Liwa al-Tawhid.

Another member of Ghurbaa al-Sham, who called himself Omar, said the Islamist alliance wanted to weaken his group because it disagrees with Islamist ideology and seeks democracy.

Illustrating his fear of Islamist cultural restrictions, Omar said he was a fan of the American heavy metal band Metallica and pulled out a mobile phone to a Metallica music video. The 24-year-old said Syrian businessmen once promised millions of dollars to bring Metallica to Aleppo but, in the end, the government rejected the plan.

"Jabhat al-Nusra wouldn't want this either," he said.

So far the Islamist groups have been the ones to attract outside support, mostly from private Sunni Muslim backers in Saudi Arabia, according to fighters in Syria.

With the help of battle-hardened Sunni Iraqis, these groups have been able to gain recruits. "They had military capabilities. They are actually organized and have command and control," said Zelin of the Washington Institute for Near East Policy.

As moderate rebel groups dithered, so did their backers outside the country. Bickering among the political opposition, a collection of political exiles who have spent many years outside Syria, also presented a problem for the United States about whether there would be a coherent transition to a new government if Assad fell.

But most importantly, Western powers fear that if weapons are delivered to Syrian rebels, there would be few guarantees they would not end up with radical Islamist groups, such as Jabhat al-Nusra, who might one day use them against Western interests.

The moderates are losing ground. In many parts of rebel-held Aleppo, the red, black and green revolutionary flag which represents more moderate elements has been replaced with the black Islamic flag. Small shops selling black headbands, conservative clothing and black balaclavas have popped up around the city and their business is booming.

Reuters met several Islamist fighters who had left more moderate rebel brigades for hardline groups. One member of Ahrar al-Sham, who would only speak on condition of anonymity, said: "I used to be with the Free Syrian Army but they were always thinking about what they wanted to do in future. I wanted to fight oppression now."