ZAKHO, Iraq — The afternoon before his family fled the onslaught of Sunni militants, Dakhil Habash was visited by three of his Arab neighbors. Over tea, his trusted friend Matlul Mare told him not to worry about the advancing fighters and that no harm would come to him or his Yazidi people.
The men had helped one another over the years: Mr. Mare brought supplies to Mr. Habash’s community in the years after the American invasion, when travel outside their northern enclave was too dangerous for Yazidis. Mr. Mare bought tomatoes and watermelon from Mr. Habash’s farm and sometimes borrowed money.
But his friend’s assurances did not sit right with Mr. Habash. That night, he gathered his family and fled. Soon afterward, he said, he found out that Mr. Mare had joined the militants and was helping them hunt down Yazidi families.
“Our Arab neighbors turned on all of us,” said Mr. Habash, who recounted his story from a makeshift refugee camp on the banks of a fetid stream near the city of Zakho, in Iraqi Kurdistan. “We feel betrayed. They were our friends.”
It would be the last time the men saw each other, as they were swept into different spheres of Iraq’s fracturing sectarian landscape, where militants from the Islamic State in Iraq and Syria are filling their ranks with the country’s disenfranchised Sunni Arabs.
Some Iraqis fear that the plight of the Yazidis, thousands of whom are missing or have been massacred by ISIS fighters, could be a harbinger of a return to the sectarian nightmare of 2006 and 2007, when neighbors turned against neighbors.
Many Sunni tribes have not supported ISIS’s advance. But the group has benefited from widespread bitterness among Sunni Arabs over perceived mistreatment at the hands of the Shiite-led government of Prime Minister Nuri Kamal al-Maliki. When ISIS arrived, officials say, some Sunnis saw an opportunity to reclaim some of the supremacy they enjoyed under Saddam Hussein’s rule.
As ISIS has advanced, more than 400,000 Yazidis, who follow an ancient religion with roots in Muslim and Zoroastrian traditions, have been forced to flee their enclaves. The humanitarian crisis helped prompt President Obama to authorize American airstrikes to halt the slaughter, a decisive step in checking the militants’ advance across northern Iraq.
“I called my closest friend after we fled, an Arab man who owned a shop in our village,” said a Yazidi man who identified himself only as Haso, declining to give his first name out of fear of reprisal. “When I asked him what he was doing, he told me he was looking for Yazidis to kill.”
The friend denied Haso’s account. But he grew angry when a journalist referred to the militant group as ISIS, because the militants now prefer to be called the Islamic State.
Another Yazidi refugee, Qasim Omar, said that just before ISIS reached his village, Arab neighbors began flying the group’s black flag from their homes.
“Before ISIS came, the Arab villagers had already helped them,” said Mr. Omar, 63. “I couldn’t believe it. They were our brothers.”
The extent of the collusion is hard to map. Many Yazidi families interviewed did not have firsthand information of Arab neighbors aiding ISIS. And in some cases, Arabs risked their lives to save persecuted friends.
But amid the chaos, an emotional truth has emerged: ISIS has destroyed the peaceful coexistence that many northern towns once cherished.
“We would like to go back to our village, but we will never have a relationship with the Arabs anymore,” Mr. Habash said. “It will never be the same.”
His realization began on Aug. 4, when Mr. Mare and some other neighbors who lived near his family’s farm came to his door, seemingly making the rounds of all of their Yazidi neighbors.
Over tea, the men told the family to remove their flag supporting the Kurdish Democratic Party and replace it with a white one.
“You will be safe,” Mr. Mare repeated, according to Mr. Habash and other family members who were present.
The men left at sunset and the family waited, Mr. Habash said.
A few hours later, calls began to pour in from friends as nearby villages fell to ISIS. The Kurdish pesh merga security forces were retreating. Men were being executed. Women and children were vanishing. At 2 a.m., the family fled.
But Mr. Habash’s niece stayed behind with her husband’s family.
“Her new family trusted the Arabs more than they trusted us,” said her father, Mohsin Habash, who stayed behind for his daughter.
The rest of the family raced toward the Yazidi enclaves at Mount Sinjar, but discovered that the road to the Syrian border was still open, and headed there instead. That evening, they arrived at a border checkpoint, among a caravan of trucks swollen with passengers collected along the way.
Later, they headed into Iraqi Kurdistan, where they received a call from a fellow Yazidi who had been stopped at a snap checkpoint set up by the militants. Manning the roadblock was an armed crew of ISIS fighters and local Arabs, among them Mr. Mare.
“He asked me why I was leaving, and I told him I needed to see my family members,” said Nasr Qasim Kachal, the friend.
“Then go to hell,” Mr. Kachal, reached by phone, recalled Mr. Mare saying before he was waved through.
Mr. Habash’s niece, Ahlan Mohsin Kalo, was not as lucky. She and her family stayed for two days before deciding to flee. But on their way out of town, Mr. Mare spotted them, according to villagers and Mr. Kachal.
Her father has not heard from her since. “They didn’t have time to run,” Mohsin Habash said.
Though Mohsin Habash’s family suffered because of one Arab neighbor, he pointed out that they were saved with the help of another: a longtime friend who led a convoy of Yazidi refugees to safety at great risk.
The convoy drove through the night, passing ISIS-controlled territories undetected. Mohsin Habash believes it was because his friend knew the Arab areas better than any of the Yazidis.
Hours later, they reached Syria. From there, Mohsin Habash’s friend introduced them to another Arab man who took the group to the border with Kurdistan.
“He saved us,” Mr. Habash said.