“I do not think the siege of Raqqa will be as long as Mosul,” says Awad, an Arab fighter in the US-backed Syrian Democratic Forces (SDF), who belongs to a military unit attacking Raqqa, the de facto capital of Isis in Syria. In an exclusive interview with The Independent, he says that “we are advancing quickly and the geographical nature of Raqqa is different from Mosul”.

The SDF has launched the crucial battle for Raqqa, a city with a population of 300,000 on the north bank of the Euphrates, after a long delay imposed by threats of military intervention by Turkey, which denounces the 45,000-strong SDF as “terrorists” dominated by the Syrian Kurds. The Turkish priority is to prevent the consolidation of a quasi-independent Kurdish statelet in northern Syria. Turkish Prime Minister Binali Yildirim today hinted strongly at Turkish military intervention, saying that “we will immediately give the necessary response if we come across a situation in Raqqa ... that threatens our security”.

​Awad, 32, comes from Raqqa but fled to Tabqa to the west of the city last year before it was captured by the SDF and four months ago joined the SDF, which the US says has 13,000 Arab fighters in its ranks. In a phone interview, he gives a vivid description of conditions on the front line, which the SDF Raqqa Operations Room says is 3km away from Raqqa to the west and north and 1km away to the east. The US estimates that there are between 3,000 and 4,000 Isis fighters in Raqqa, who are isolated there because US coalition air strikes on 3 February destroyed the last two bridges linking it to the south bank of the Euphrates. The fighters can only cross the river by boats, but they would then be vulnerable to air attack.

“They [Isis] are mostly withdrawing [into Raqqa], though some are fighting fiercely and do not leave their positions until they are killed,” says Awad. “We killed dozens when we liberated al-Mansoura [west of Raqqa] and Baath Dam [on the Euphrates, renamed Freedom Dam by the SDF]. In addition, we repelled many counter-attacks by Isis since the Tabqa battle until now.”

The SDF captured the Tabqa Dam, the largest in Syria at the southern end of Lake Assad, and the nearby town of Tabqa, 25 miles west of Raqqa, on 10 May, ending a stalemate that had lasted for several weeks. The US decided in May to give the SDF additional military assistance including armoured cars, anti-tanks weapons, mortars and heavy machine guns, despite strong opposition from Turkey. The Turkish government had claimed that its proxy forces inside Syria, backed by the Turkish army, could replace the SDF as the main US military ally in Syria against Isis, but the US did not consider this a realistic option.

Though Isis units have been retreating in the face of SDF advances and US-led air strikes, the jihadis are still resisting strongly. Awad says that “last week, Isis fighters attacked us from behind in a village called Abu Qebab, east of Raqqa. They were hiding in a tunnel that had not been checked yet by our comrades. In that attack, we surrounded them from two sides and killed about 10 of them.”

The state of play in late May, as the SDF closed in on Raqqa from the north, east and west. Baath Dam has since been captured and the SDF says it is within 1km of the city to the east (GraphicNews)

It should become clear in the next few days if Isis will try to defend Raqqa strongly and risk losing many of its experienced fighters. In Mosul, Isis has fought skillfully using an innovative mix of urban guerrilla tactics that has withstood Iraqi government forces for seven months. When Isis was previously fighting for two other big cities, Ramadi and Fallujah, in Anbar province west of Baghdad, it resisted most strongly in the villages and countryside around them, but not in the built-up areas in the city centres.

But in Mosul, where the siege began on 17 October last year, Isis fighters have reversed this approach, holding the periphery of the city lightly and concentrating its fighters in the centre. It tries to avoid its positions being identified from the air and destroyed, by using a mixture of mobile sniper teams, swiftly changing their positions by means of holes cut in the walls of houses, along with suicide bombers in vehicles, mines, booby traps and mortars. This has succeeded in slowing down and inflicting heavy casualties on the advancing Iraqi security forces.

In Pictures: The crisis unfolding in Syria Show all 30 1 /30 In Pictures: The crisis unfolding in Syria In Pictures: The crisis unfolding in Syria A Syrian family arrives at a checkpoint, manned by pro-government forces, at the al-Hawoz street roundabout, after leaving Aleppo's eastern neighbourhoods Getty In Pictures: The crisis unfolding in Syria A Syrian woman, fleeing violence in the restive Bustan al-Qasr neighbourhood, reacts as she stands with her children in Aleppo's Fardos neighbourhood, after regime troops retook the area from rebel fighters Getty In Pictures: The crisis unfolding in Syria Syrian pro-regime fighters, gesture as they drive past resident fleeing violence in the restive Bustan al-Qasr neighbourhood, in Aleppo's Fardos neighbourhood Getty In Pictures: The crisis unfolding in Syria Syrian rebels withdrew from six more neighbourhoods in their one-time bastion of east Aleppo in the face of advancing government troops, the Syrian Observatory for Human Rights said Getty In Pictures: The crisis unfolding in Syria Syrian rebels withdrew from six more neighbourhoods in their one-time bastion of east Aleppo in the face of advancing government troops, the Syrian Observatory for Human Rights said Getty In Pictures: The crisis unfolding in Syria Syrian residents, fleeing violence in the restive Bustan al-Qasr neighbourhood, arrive in Aleppo's Fardos neighbourhood , after regime troops retook the area from rebel fighters Getty In Pictures: The crisis unfolding in Syria Syrian pro-regime fighters, gesture as they drive past residents fleeing violence in the restive Bustan al-Qasr neighbourhood, in Aleppo's Fardos neighbourhood Getty In Pictures: The crisis unfolding in Syria Syrian residents, fleeing violence in the restive Bustan al-Qasr neighbourhood, arrive in Aleppo's Fardos neighbourhood, after regime troops retook the area from rebel fighters Getty In Pictures: The crisis unfolding in Syria Syrian residents, fleeing violence in the restive Bustan al-Qasr neighbourhood, arrive in Aleppo's Fardos neighbourhood Getty In Pictures: The crisis unfolding in Syria A Syrian pro-regime fighter speaks with a child, as residents flee violence in the restive Bustan al-Qasr neighbourhood. Syrian rebels withdrew from six more neighbourhoods in their one-time bastion of east Aleppo in the face of advancing government troops AFP/Getty Images In Pictures: The crisis unfolding in Syria Smoke rises as seen from a governement-held area of Aleppo, Syria Reuters In Pictures: The crisis unfolding in Syria Syrian soldiers targeting rebels-held areas in the eastern neighborhoods in Aleppo, Syria. According to media reports, the army is now holding on 99 percent of Aleppoís eastern neighborhoods EPA In Pictures: The crisis unfolding in Syria Syrian pro-government forces patrol Aleppo's eastern al-Salihin neighbourhood after troops retook the area from rebel fighters Getty In Pictures: The crisis unfolding in Syria Syrian soldiers rest following the battle at al-Sheik Saeed neighborhood in Aleppo, Syria EPA In Pictures: The crisis unfolding in Syria A Syrian pro-government fighter walking past closed shops in the Bab al-Nasr district of Aleppo's Old City. Once renowned for its bustling souks, grand citadel and historic gates, Aleppo's Old City has been rendered virtually unrecognisable by some of the worst violence of Syria's war Getty In Pictures: The crisis unfolding in Syria The crucial battle for Aleppo entered its 'final phase' after Syrian rebels retreated into a small pocket of their former bastion in the face of new army advances. The retreat leaves opposition fighters confined to just a handful of neighbourhoods in southeast Aleppo, the largest of them Sukkari and Mashhad Getty In Pictures: The crisis unfolding in Syria Syrian civilans arrive at a checkpoint, manned by pro-government forces, at the al-Hawoz street roundabout, after leaving Aleppo's eastern neighbourhoods. Syria's government has retaken at least 85 percent of east Aleppo, which fell to rebels in 2012, since beginning its operation Getty In Pictures: The crisis unfolding in Syria Syrian civilians flee the Sukkari neighbourhood towards safer rebel-held areas in southeastern Aleppo Getty In Pictures: The crisis unfolding in Syria Syrians celebrate in the government-held Mogambo neighbourhood of the northern Syrian city of Aleppo, after rebel fighters retreated into a small pocket of their former bastion in the face of new army advances Getty In Pictures: The crisis unfolding in Syria Syrians celebrate in the government-held Mogambo neighbourhood of the northern Syrian city of Aleppo, after rebel fighters retreated into a small pocket of their former bastion in the face of new army advances. The fall of Aleppo would be the worst rebel defeat since Syria's conflict began in 2011, and leave the government in control of the country's five major cities Getty In Pictures: The crisis unfolding in Syria A Syrian refugee camp in the Bekaa Valley, Lebanon, close to the Syrian border PA wire In Pictures: The crisis unfolding in Syria Syrian refugee Aliya inside the tent where she lives with her husband and ten children in a camp in the Bekaa Valley, Lebanon, close to the Syrian border PA wire In Pictures: The crisis unfolding in Syria Syrian refugee women and children outside the entrance to their tents in the refugee camp in the Bekaa Valley, Lebanon, close to the Syrian border PA Wire In Pictures: The crisis unfolding in Syria A Syrian refugee camp in the Bekaa Valley, Lebanon, close to the Syrian border PA wire In Pictures: The crisis unfolding in Syria A Syrian refugee camp in the Bekaa Valley, Lebanon, close to the Syrian border PA Wire In Pictures: The crisis unfolding in Syria A Syrian refugee woman outside the entrance to the tent where her family live, in the refugee camp in the Bekaa Valley, Lebanon, close to the Syrian border PA wire In Pictures: The crisis unfolding in Syria A vehicle drives past a mosque at night in Idlib, Syria. Picture taken with a long exposure Reuters In Pictures: The crisis unfolding in Syria Damaged buildings stand in the rebel-controlled town of Binnish in Idlib province, Syria Reuters In Pictures: The crisis unfolding in Syria The night sky is seen through damaged windows in the rebel-controlled town of Binnish in Idlib province, Syria Reuters In Pictures: The crisis unfolding in Syria Damaged buildings stand in the rebel-controlled area of Maaret al-Numan in Idlib province, Syria Reuters

Isis may use the same tactics in Raqqa and seek to draw out the siege, but the city is a geographically smaller and less populous than Mosul which had a population of 1.3 million before the siege. Awad does not believe that the siege of Raqqa will be as prolonged as in Mosul and suspects that the determination of the Isis defenders may not be as high as in Iraq. He says that “the SDF made two calls last month for Isis to surrender, but those that did so were locals. No foreigners have surrendered so far.”

Some of the Isis units are composed of foreigners who cannot blend into the local population, or expect much mercy, if they surrender. “I have been told by our officers that all the Isis snipers killed by our forces are foreigners,” says Awad. “We lost some of our commanders because of these snipers and a few days ago one of our snipers killed an Isis sniper when we fought in Mansoura, west of Raqqa.”

Syrian army 'crosses into Raqqa province'

The firepower and military expertise of the SDF is much enhanced by US support: “The US-led coalition air strikes and forces are working efficiently with us, we have many American experts who train our commanders and officers and instruct them in using new technical devices. We also have heavy weapons and armoured vehicles. Every week we receive many weapons on the three fronts around Raqqa.” This supply of modern weapons, and expertise on how to use them, will determine not only the fate of Raqqa but the future ability of the Syrian Kurds to stand up to Turkish military intervention or action by President Bashar al-Assad’s forces, which are advancing into Isis-held eastern Syria.