A boatman drives from the besieged town of Thuluyah, Iraq, which is now accessible only from the Tigris. (Loveday Morris/The Washington Post)

The metal-hulled boats carry out the wounded for treatment, as well as fruit to sell at market. Coming in, they bring supplies of cooking gas, medicine and ammunition.

Cocooned in a bend in the Tigris River, this town shaded by orange trees and date palm groves has long relied on the waterway. But since Islamic State militants blew up the last bridge into Thuluyah last week, the river is the only way in or out — complicating efforts to resupply and reinforce beleaguered fighters here.

Thuluyah, 45 miles north of Baghdad, has held out for more than three months against the Sunni extremists attempting to expand the Iraqi territory they hold. But in a conflict that is often framed as Sunni vs. Shiite, here Sunni tribesmen are turning against militants who claim to fight for their religion.

Tribal leaders hold the town up as an example of how the conflict with the Islamic State can be won, as the war brings together unusual allies against a common enemy. In some Sunni-dominated towns, residents welcomed the Islamic State as it advanced in the past three months. But Sunni tribesmen, the police and the Iraqi army fight side by side on the front lines of Thuluyah. In recent weeks they have been joined by Shiite militias that are notorious for revenge killings of Sunnis.

“We asked for their help and now we are dying together,” said Abed Mutlaq al-Jabbouri, a tribal leader. “This situation has imposed a new reality: Everyone is fighting Islamic State. There are no Sunnis, no Shiites. We are all sons of Iraq.”

Boats load and unload on the banks of the Tigris. The Sunni town of Thuluyah has been cut off by land since the besieging Islamic State fighters blew up the final river bridge recently. (Loveday Morris/The Washington Post)

Scarred by battle

Although the southern tip of Thuluyah retains its oasis-like charm, its main street, once home to a bustling market, bears the scars of battle. A large crater gapes in the road near the main mosque, distinguished by its turquoise-tipped minaret. An explosives-laden Humvee driven by a suicide bomber killed more than 20 people here this month. Another had blasted a way for it through the front lines minutes before.

An amusement park on the peninsula’s east side now serves as a front-line position for tribal fighters, police and a smattering of Iraqi soldiers, just hundreds of yards from the Islamic State’s sphere of control. The militants crossed the river in an assault this month, speeding in dinghies similar to the ones that ferry supplies into the town, witnesses said. The militants attacked again Thursday, residents said.

Hazem Abdel-Razzak, a 40-year-old soldier dressed in fatigues, has been fighting in Thuluyah, also commonly transliterated as Dhuluiya, for more than 100 days. He is from Balad, a Shiite city across the waterway. He said he was not officially dispatched here but came as a volunteer.

“We are all together,” said Hikmet Faisal Ali, a Sunni tribal fighter standing next to Abdel-Razzak.

It’s a marriage of convenience, and it’s unclear how long the alliance will last.

Abbas Sadr, an 18-year-old fighter with Kataib Hezbollah, the Shiite militia with the biggest role in the town, guards the jetty in Balad. “We went in [to Thuluyah] when they asked us to. Before that, they had rejected us,” he said. “They were really trapped.”

Now, the residents of Thuluyah are even more trapped. A week ago, militants managed to blow up the last wooden crossing into the town. It was their fourth attempt, residents said. The attackers drove an explosives-packed boat in a suicide mission — detonating it under the bridge.

This time they shielded the boat in metal, protecting it from bullets fired by the Thuluyah forces.

The town’s main bridge across the Tigris had been taken out during a suicide bus bombing in July.

‘Now they will kill us all’

The U.S. and Iraqi government strategy for confronting the Islamic State extremists centers on co-opting tribes such as the Jabbours.

But unlike some of their neighbors, the Jabbour tribe has a long history of fighting Sunni extremists.

Still, this town was once a fertile recruiting ground for al-Qaeda. Among its date palms, the U.S. military launched one of its first counterinsurgency efforts against Sunni extremists in 2003. Thuluyah had been a base of support for Saddam Hussein’s Baath Party, and hatred of the American occupation ran deep.

But when Nadhim Khalil al-Jabbouri, an al-Qaeda operative and prominent cleric, broke with his paymasters in 2007, it was a turning point, residents say. He later led efforts to oust his former allies under the Awakening Movement, the U.S. project to turn Sunni tribesmen against al-Qaeda.

“In each house in Thuluyah, you can find a story about al-Qaeda and what they’ve done to us,” said Karim Abu Muthanna, also a local sheik. In his case, the story took place on his farm in 2008, when al-Qaeda militants shot his son in front of him and took him and another son hostage.

“Only the Jabbour [tribe] resisted them,” said Abed Mutlaq, the tribal leader. He sees little difference between al-Qaeda and the Islamic State, which was inspired by Osama bin Laden’s organization but has since been disowned by it. “If they come inside [the town] now, they will kill us all, even the child in its mother’s womb,” he said of the breakaway group.

But the Thuluyah residents’ pact with their enemies’ enemy is hardly typical. In much of Iraq, mistrust between Sunnis and Shiites runs deep.

The Khazraji and Bufarraj tribes, which control outlying parts of the town to the north, capitulated to the Islamic State when the militants entered the area, residents in Thuluyah said.

“Three months ago we used to marry them. We used to visit their homes,” said Barzan al-Jabbouri, a tribal marksman wearing flip-flops. He said that three months ago, he was a university lecturer. “Now we kill each other.”