Kurdish and Arab forces backed by the US have entered Islamic State’s de facto capital of Raqqa, setting the stage for what could be a months-long campaign to reclaim the militants’ largest stronghold in Syria.



The Syrian Democratic Forces (SDF), a coalition of Kurdish and Arab fighters, breached the outer city limits of Raqqa, seizing a 1,000-year-old fortress in the west and a neighbourhood on the eastern side of the city, two days after announcing the start of the offensive.

“Raqqa to them is the capital of the caliphate, and they [Isis] have fortified it to a great extent,” Nouri Mahmoud, a spokesman for the People’s Protection Units (YPG), the Kurdish militia taking part in the assault, told the Guardian.



The operation – codenamed Operation Wrath of Euphrates – to reclaim Raqqa is led by the SDF, whose largest component is the YPG, and is backed by US air power. If successful, it would deprive Isis of its second largest city, with a simultaneous campaign to take back Mosul in Iraq also under way.

It would be a major blow to the militant group’s efforts to take advantage of chaos in Iraq and Syria, three years after it declared a caliphate across the borders of both nations.

But forces on the ground face major challenges in their advance, including what Mahmoud described as an effort by Isis to use civilians to slow down the SDF’s advance, numerous mines both outside and inside the city, booby traps, vehicles wired with bombs, a network of tunnels under the city, and suicide bombers.



“They are taking all sorts of measures because they know losing Raqqa is the beginning of the end for Daesh,” he said, using another common name for the group. “So in any areas they see advances, they are using the civilians.”



The campaign in Raqqa has been a long time in the making. The US administration of former president Barack Obama had favoured using the SDF as the spearhead of the assault, a prospect that angered Turkey, which considers the YPG militia a terrorist group affiliated to the insurgents within its own borders, the Kurdistan Workers’ party (PKK).

Ankara had argued that Raqqa ought to be liberated by a primarily Arab force and has launched its own military intervention into northern Syria, with which it shares a 500-mile border.

But the Donald Trump administration gave the go-ahead last month for the direct arming of the YPG in preparation for the Raqqa campaign, signalling that his government wanted the SDF to take the leading role.

Mahmoud said the US-led coalition against Isis was supporting the ground operation from the air, but that American special forces stationed in the area had not entered the city.