In the Nineveh Plains, near Mosul, Iraq, some 32,000 Christians live in areas controlled by Iran-backed militias. As tensions between the United States and Iran, Nineveh Christians hope for an end to the influence of Iran in their day-to-day lives.

With the liberation of parts of Iraq from ISIS in 2017, Iraq's Syriac and Chaldean Christians returned home to two unwelcome developments. First, unsurprisingly, their homes had been burned, looted or destroyed by ISIS. Second, Iran-backed groups who helped defeat ISIS--known as Popular Mobilization Forces--now controlled the towns their ancestors had inhabited for more than a millennia.

Today, the largest Christian town, Baghdeda as it is called by Christians--it is also known as Qaraqosh--is surrounded by an Iran-funded militia. The second-largest town, Bartella, is controlled by such a militia. Both are around 20 minutes from Mosul, where Abu Bakr al-Baghdadi had declared the doomed ISIS caliphate in 2014.

This picture is complicated by a demographic shift also taking place in these communities--once largely Syriac Christian and now Shabak Muslim. The Shabak are primarily a Shiite minority who, like Christians and Yazidis, were persecuted by ISIS.

This demographic shift is most pronounced in Bartella, which sits on the crucial artery road between Erbil and Mosul. As recently as 2003, Bartella was 95 percent Christian. In the space of a decade, it has become majority Shabak, and members of this religious and ethnic community now control the town's government and checkpoints into the city through their wing of the P.M.F., the Shabak Militia. Today, this militia receives arms, vehicles and money from Iran.

Amjad, 33, a Syriac worker in an electricity shop, complained of treatment as a second-class citizen by this militia. "Frankly speaking, if they had the chance, they'd take everything from us," he said of the Shabak Militia. "If they have the chance to attack, they'd do more damage than ISIS did."

(Pseudonyms have been used for most of the people interviewed for this article to protect them from reprisals.)

Like many Christians, he thinks the Shabak P.M.F. is corrupt. "A few days ago, there were some P.M.F. members at the gas station. The gas station was providing 40 liters to each person, but they provided more than that to their members or relatives."

Christian business owners, in particular, are targeted by the P.M.F., who demand bribes for allowing goods through at checkpoints or opening a shop. "At the checkpoint toward Erbil, which they control, they don't let some cars go through without a bribe of $1,000," said Amjad.

Some locals complain of restrictions on free movement. "I have a business partner from Mosul," said George, 31, an electronics shop owner. "A few days ago, they stopped him at the checkpoint and refused to let him in."

Christian businesses are also affected by a supposed boycott on the part of Shabak residents. Bashar, 35, a security guard, claimed, "The Shabak only purchase from the Shabak, and they tell others not to purchase from Christians." Others make the same claim, including Amjad, who added that the Shabak Militia deliberately set fire to wheat and barley fields in the summer. Although these events, well-documented in the press, were widely attributed to ISIS, the lack of security makes it difficult to establish responsibility for such events.

Kamal, 60, a shop owner, said that the Shabak, including members of the P.M.F., have stolen wheat from his shop twice, a story corroborated by one other interviewee and confirmed by security camera footage. "There is no future for Christians in Iraq," he said.

Although the same pattern of harassment and discrimination that began in 2017 continues in Bartella, locals disagree on the specific impact of rising U.S.-Iran tensions in December and January.

Some believe that the tensions have led to more scrutiny of Christians at Shabak-controlled checkpoints, especially since Christians are associated with Americans. "It's increased their hatred because they consider America a Christian country," said Amjad. He cited an incident in January when, after leaving a funeral, a BMW driver refused to let him through a certain area. "It was clear to me that the driver was a member of the P.M.F.," he said.

Others think the militias, rattled by the assassination of Iranian commander Qassim Soleimani and anti-Iran protests in Baghdad, have dialed back the worst of their behavior. "They are afraid and weaker now," said Kamal. George said that when anti-government protests began in Baghdad in October, the P.M.F. militia members stopped demanding bribes at checkpoints.

The Most Rev. Petros Mouche, Syriac Catholic archbishop of Mosul, told America that "the tensions between Iran and the U.S. haven't changed anything for now, but that doesn't mean the situation is good."

"As long as the presence and influence of Iran remain in Iraq and especially in the Nineveh Plains, there is a risk of more problems and difficulties in co-existing peacefully with our neighbors," he said.

The recent disappearance of four employees of the Catholic aid group SOS Chrétiens d'Orient in Baghdad on Jan. 20 has only added to Christian anxiety in the north. One employee was a Syriac Catholic, who may be the first Christian from Baghdeda to have been taken by an Islamist group since 2017. The remaining three were French nationals. SOS Chrétiens d'Orient has organized a prayer campaign for their safe return.

Although it is impossible to discount ISIS being involved, the Baghdad area is mostly controlled by Iran-backed militias. They have kidnapped dozens of protesters since October, when anti-government demonstrations began. These protests initially focused on jobs and government corruption, but they have also included a strong anti-Iran component.

"Everyone is not only saddened by the disappearance of the three French men and their companion, but this has also increased our fear and our uncertainty in the future--whatever group it is that's responsible for this drama," said Archbishop Mouche.

Ali Almikdam, an Iraqi journalist and human rights activist, thinks it likely an Iran-backed group is involved. "The Hezbollah Brigades militia has previously kidnapped journalists," Mr. Almikdam said. "The first possibility is that they will be in a Hezbollah prison in Baghdad."

The Hezbollah Brigades are allied with the League of the Righteous, a separate Iran-backed group with an office in Bartella.

If the employees of SOS Chrétiens d'Orient were taken by an Iran-linked group, it would be an unusual development. Many Shiite Islamist groups, unlike their Sunni counterparts, at least publicly profess to esteem the role of Christians in Iraq. While intimidation, looting and extortion are common, disappearances at the hands of such groups are infrequent and difficult to confirm. In January, two French journalists were briefly kidnapped in Baghdad, likely at the hands of the Hezbollah Brigades.

The most direct consequence of rising insecurity is practical: emigration. Large numbers of Christians who returned after ISIS was driven off have decided to abandon the effort to re-establish themselves in the communities of the Nineveh Plains. They are leaving for the United States, Australia or Europe. This problem is especially pronounced in Baghdeda. Although the economy is poor, emigrants overwhelmingly say it is the poor security and sectarian tensions that are driving them out of Nineveh. Many residents say that emigration would slow or stop if the national Iraqi security forces, rather than the P.M.F., controlled the area.

"If the current situation remains the same, things will get worse," said Bashar. "There will be no future in Bartella since they control everything here."

While George pauses to say that not all Shabak are bad, he, like many other Christians, offers the same policy prescription. "We don't need either the P.M.F. or the Shabak. They are both related to Iran. We want them out."

Additional reporting by Rami Esa Saqat and Fadi Esa Saqat in Iraq.