A BLACK flag flies over the governor’s headquarters in Raqqa, a city of 250,000 people in Syria’s north-east which is the biggest so far that the rebels have captured wholesale from President Bashar Assad’s regime. It is also a base for Jabhat al-Nusra (Victory Front), an extreme armed opposition group in Syria with which al-Qaeda in Iraq recently claimed to have merged. But the group does not dominate Raqqa. At least four other rebel outfits, mainly Salafist ones whose members say they want to emulate the companions of the Prophet Muhammad, vie with a bunch of civilian councils for power over this tribal Sunni city, plastering its walls with rival graffiti. Yet in the eastern provinces as a whole, Jabhat al-Nusra has emerged as a hugely powerful presence. Among rebel fighters across the country it is probably the most effective single group.

By contrast, down the road in the gold-curtained living room of a small house near the city centre, members of a more moderate Islamist lot, al-Farouq, admit that they have grown weaker. They used to control the border crossing into Turkey at Tel Abyad, a prime piece of territory for arms and money, along with another crossing farther west. But that has since been grabbed away from them.

Sometimes Jabhat al-Nusra imposes itself on other rebels by force. Two months ago it tried to assassinate Abu Azzam, the local Farouq unit’s bear of a leader. In the event he had to flee to Turkey, while his men were left directionless and disorganised. Funds and weapons, which one Farouq member says only ever came in “injections just often enough to keep us alive”, dried up.

Raqqa offers a snapshot of what is going on among the rebels elsewhere in Syria. The more moderate ones are now a minority. On one side they have been squeezed by Salafist factions, especially in the rebel-controlled east. On the other, they have been pushed back territorially by the regime as it regains ground in the more populated west of the country.

That is partly because Mr Assad’s allies, Iran and Hizbullah, the Lebanese Shia movement, have backed the regime with more dedication than the Gulf Arab and Western states have helped the opposition. As the civil war has dragged on, the rebels, hardened by war and seeing where their bread is buttered, have become more Islamist and extreme.

For Western governments pondering whether to arm the rebels rather than merely advise them and provide non-lethal support, Jabhat al-Nusra is the biggest worry. By some estimates, it now has 6,000 carefully vetted men, mainly Syrians but under foreign leadership. Its global jihadist ideology justifies violence to bring about a nation where all Muslims unite. “Most groups are a reaction to the regime, whereas we are fighting for a vision,” explains one of its fighters. Though Jabhat al-Nusra says it gets most of its weapons from the spoils of battle, it also enjoys murky sources of private funding, including regular payments from al-Qaeda in Iraq. Since it captured oil wells and grain silos, it has been able—more effectively than other outfits—to set up basic services and a rudimentary administration in the areas it controls, as well as sell off goods and oil for cash. It is probably the most disciplined of all its rivals. But it may not be as strong as its reputation suggests. The al-Qaeda announcement, which emanated originally from its ally in Iraq, may have harmed it. Ructions within the ranks broke out between those who favour the link and those who are against it, says a sheikh who deals with the organisation. Civilians in some areas who had started to welcome the group because of its military prowess and provision of services have protested against the al-Qaeda tie. Even Ahrar al-Sham, another large nationwide network of Salafist jihadists, criticised the affiliation. Yet it is not only Jabhat al-Nusra which expresses extreme Islamist views. Though Ahrar al-Sham has more local aims, its comrades are also vehemently Islamist. So are many of the other forces that have gained ground among the rebels, thanks in part to Gulf backing.

Rebel groups that echo more moderate and secular attitudes, for which Syria used to be praised, are smaller and less powerful. Other umbrella groups, such as Liwa al-Tawhid in Aleppo, Syria’s embattled second city, are harder to classify, in part because they serve as franchises or bring together smaller groups with a range of ideas. The Farouq Battalions, whose territorial reach goes from Homs, the pivotal third city between Damascus and Aleppo, to Hasaka in the north-east, is another mixed bag, ranging from Islamists to people with no particular ideology. “What does Islamist mean?” asks Omar al-Dada, a doctor who heads a small, independent fighting group in Raqqa province. “For me, and most Syrians, it just means I am a Muslim. I want a democracy and Islamic law to rule over family matters only.”