The road into the city of Kirkuk is lined with peshmerga, police, and flames — they continually shoot out of the ground as natural gas seeps up and ignites. On the road, dozens of cars wait at a checkpoint while peshmerga halt and question each driver: "Kurdi? Arabi?"

Kurds are waved in, while Arabs are pulled over, searched, and interrogated; the men stand in front of their car windows with crossed arms and grim faces, shielding the women and children inside. Some argue. Only a few make it through. The line of cars grows.

Kurds are leading the battle against the Islamic State — known as Daash in the region — in northern Iraq, particularly in places like Kirkuk, which has been under peshmerga control since the Iraqi army fled an Islamic State advance in June. Kurdish peshmerga and asayish [security] forces are now forced to fend off the Sunni militant group on the front lines, which are as close as 7 1/2 miles from Kirkuk's center, and inside the city in the form of insurgent cells.

Kurdistan has taken in hundreds of thousands of displaced people, many of them Yezidis and Christians who now fill the churches and schools of Ankawa and Dohuk. But as international airstrikes increasingly compel Islamic State fighters to adopt guerrilla tactics, Kirkuk faces a rising threat of militants hiding among civilians — especially the 129,500 displaced people fleeing Islamic State-held areas, most of whom are Sunni Arabs. Their presence is both a humanitarian challenge and a security threat — people without shelter or aid who are suffering among insurgents who are initiating sectarian killings and bombings.

Sectarian distrust runs deep in Kirkuk, which has both oil wealth and a history of ethnic cleansing. Inside the city, 73-year-old shopkeeper Hassan Abdulghafour recounts to VICE News the times he's been forcibly displaced: from his home village to Kirkuk in the 1960s, then to Erbil in 1988, and then to Iran in 1992 while fleeing Saddam Hussein's chemical attacks and Baathist Arabization. Abdulghafour returned to Kirkuk in 2003, opening a shop and building his house as US forces invaded.

A decade later, Iraq is still burning. "I have no faith this will end unless God does a miracle," Abdulghafour said. The Islamic State are like the Baathists all over again, he added — perhaps not the same people, but people who are using similar kinds of terror, brutality, and religious manipulation.

"Saddam used to say 'Allahu Akbar' too," Abdulghafour said. "The Baathists turned against us like tigers. I don't want Arab friends anymore."

Many displaced Christians and Yezidis echo his words. Longtime Sunni neighbors suddenly turned against them when Islamic State fighters arrived, they say, looting their houses. And so few trust the Sunnis who are now seeking refuge in Kurdistan.

"The displaced people are pretending," Abdulghafour said. "They are infiltrating here as Daash. Their young people are fighting, and they plant older people here to take control. You don't know who they are or if they're telling the truth."

Five minutes from Abdulghafour's home, piles of garbage float in stagnant water near a concrete hut that houses four displaced Arab families from Baiji; 30 people spill out of the home, some sleeping outside on the ground or on the roof. The children's skin is gray with dust. Mohamad Dhahir Thiyab, a grandfather and head of the household, lies sick on a mat inside.

Photo by Alice Su

"Daash came to us like a nightmare," Thiyab said. He has three sons: Two were Iraqi police officers, which makes them Islamic State targets. A roadside bomb killed the third last year. Thiyab himself was once an officer in Saddam's army, and he rejects the idea that former Baath supporters are now with the Islamic State. "Only a few former soldiers joined Daash in my town," he said. "Mostly they were young people who weren't thinking. Daash are barbarians."

There are Islamic State supporters among the displaced Sunnis, Thiyab said. But those Sunnis who oppose the group have no defense or support. "Most military commanders abandoned their posts for no reason, and Daash started blowing up our houses," he said. "Iraq's soldiers take money instead of fighting. The militias act like Daash and kill people. It's all bullshit. No one is willing to fix it."

No one, his neighbors would agree, except the Kurds. As suicide car bombings continued in Kirkuk through the summer, asayish raided Islamic State cells and arrested militant suspects. "If not for Kurds, this would be a Daash area right now," said one asayish officer. He listed a number of recent successes — captured weapons, explosives found hidden inside houses, and arrests based off of tips from Kurds and Arabs alike. The Kurds' problem is not intelligence or capacity, the officer said, but a lack of cooperation from Iraqi police and military.

"Baghdad and peshmerga are not friends," he said.

Asayish also distrust Iraqi police. "We don't share all information with them — they are infiltrated [by the Islamic State]," the officer claimed. "We report to Kurdistan." Kirkuk's asayish forces detain suspects and then turn them over to the Iraqi police, as the city is still technically under Baghdad's authority. "But then they get released through bribery or phone threats," he said. "Or if we work with Iraqi police, suspects are already tipped off by the time they get to the arrest."

'Iraq's soldiers take money instead of fighting. The militias act like Daash and kill people. It's all bullshit. No one is willing to fix it.'

Meanwhile, killings and kidnappings, mostly of Sunni Turkmen and Arabs, are on the rise in Kirkuk. Many residents believe they are the work of Shia militias, according to a recent Amnesty International report, operating openly in Kirkuk and "parading through the city with their weapons on display." While the Shia militias tacitly fight against the Islamic State with the peshmerga, they also carry out indiscriminate attacks on civilians with no repercussions, the report says.

Displaced Arabs are allowed into Kirkuk, but only if they can produce a Kurdish _kafeel — _a resident sponsor. The kafeel must come personally to the checkpoint and vouch for the Arab, at which point peshmerga may or may not let them in. Those without kafeel are sent back to Islamic State-controlled areas.

Mohamad Khalil al-Jubouri, a member of the Kirkuk Provincial Council from Mulla Abdullah, a mostly Sunni town now under Islamic State control, said Kirkuk's humanitarian situation is urgent. "The Kirkuk government is ignoring displaced Arabs," he told VICE News. "They blame it on security, but that's just an excuse. Some council members don't want to talk about the displaced people because they don't want them here at all."

The predominant fear among Kurdish politicians is not that the Islamic State will infiltrate Kirkuk, al-Jubouri said, but that Kirkuk's population will tip in favor of Arabs; they want to keep Kirkuk part of Kurdistan. "We need to see this as a humanitarian problem, not a political one," al-Jubouri said. "No one wants to be displaced."

Members of Kirkuk's other minorities — Assyrians, Chaldeans, and Turkmen — say they are glad that Kurdish forces are defending Kirkuk from the Islamic State instead of the Iraqi army. "If we were still counting on Maliki's government, we'd be finished in an hour," said Ayad Mohammad, a local Turkmen.

"Baghdad is never going to change," Mohammad said. "With Kurdistan, we still have a chance."