HAMAM AL-ALIL, Iraq — The road to Mosul is littered with the detritus from almost three years of war: burned M1117 armored vehicles, sandbagged berms and trenches from defensive positions once manned against Islamic State fighters, houses pancaked by airstrikes. The long supply line of the Iraqi army stretches through villages, with bulldozers, camouflaged trucks and temporary base camps.
Particularly noticeable are the frequent checkpoints manned by young armed men. But the fighters often aren’t from the Iraqi army or the Federal Police, but are members of various Iran-supported Shiite militias in the Hashd al-Shaabi, or Popular Mobilization Units.
While taking part in the U.S.-backed assault on the Islamic State group’s last major stronghold in Iraq, many of these units fly flags celebrating Shiite religious figures such as the Imam Hussein, and some have posters of Iran’s supreme leader, Ayatollah Ali Khamenei.
A tour of these areas shows that Shiite militias and Iran have been empowered in the fight and that Iraq remains a state even more divided along religious and ethnic lines.
The battle for Mosul, once a city of more than 2 million residents, began in mid-October. In a lightning assault in 2014, the Islamic State, a radical Sunni Muslim group, took the city, expelled Christians and massacred Shiite and other minorities, and dynamited shrines and archaeological sites as part of its Salafi policy. When the Iraqi army began its campaign last fall, Mosul’s population had been reduced to around 1 million people.
Complicating the battle has been the presence of thousands of fighters allied with the Popular Mobilization Units. Composed of numerous militias that answered a 2014 fatwa by Iraqi Grand Ayatollah Ali al-Sistani to fight the Islamic State, the units have many leaders with shadowy pro-Iranian pasts.
Qais Khazali was a follower of Shiite cleric Muqtada al-Sadr, who attacked U.S. troops in Karbala in 2007 and now runs the Asa’ib Ahl al-Haq militia. Hadi al-Amiri, leader of the Badr Organization, fought alongside Iran’s Revolutionary Guard Corps during the Iran-Iraq War of the 1980s. Abu Mahdi al-Muhandis, leader of the Kata’ib Hezbollah militia, also fought with the Iranians in the 1980s.
In December, the PMU was incorporated as an official paramilitary force of the Iraqi government. But fears remain that its role in northern Iraq will inflame tensions with Sunni Arabs and the Kurdish population.
In an October speech, Mr. Khazali called the battle for Mosul the “revenge for the killing of Hussein.” He was referring to a historic killing that Shiites blame on Sunnis and tying it to the modern sectarian war with the Islamic State.
“If they exact widespread revenge against the Sunnis and expel them, this might create a conducive environment for ISIS to come back,” Kawa Hassan, director of the Middle East and North Africa Program at the Brussels-based EastWest Institute, told a European Parliament hearing in November.
The worst fears of mass revenge killings and expulsions have not been realized in or around Mosul to date. Instead, Shiite militias are more quietly extending their presence and visible control in a new part of the country, as a tour of the region repeatedly demonstrates.
Driving out of the Kurdish autonomous region from Irbil, the closest major city to Mosul, one leaves the Kurdish flags behind and immediately enters the uncertain terrain of militias. In the Christian town of Hamdaniyeh, the Nineveh Plains Protection Units, a Christian militia paid by and affiliated with the PMU, guards the entrance and exit. Its members are relaxed and friendly. Most of them live in the Kurdish region, where they fled the Islamic State and have only recently returned.
After Hamdaniyeh, the road crosses hillocks and fields with long-dilapidated chicken coops and the militias are from a Shabak unit. The Shabak are a local minority, some of whom are Shiite and recently joined the PMU’s Badr Organization.
For some Shabak and Iraqi Christians, the PMU are liberators. Last year, the PMU released a video showing the church bells of Mosul ringing again, sending the message that they would liberate the city from the Islamic State and make it safe for Christians. Militia members hand out “Imam Hussein” flags to children in local hamlets.
But in some Sunni Arab villages, there is obvious fear of the militia members who wander the streets, rifles over their shoulders, peering into mud-caked compounds.
Leaving the Shabak behind, the road skirts the ruins of the ancient Assyrian city of Nimrud, which Islamic State fighters blew up in 2015. A floating pontoon bridge over the Tigris is all that connects the western and eastern sides today. Airstrikes have demolished the old bridges.
The pontoon bridge is in such bad shape that it washed out during flooding in April and took days to repair. Civilians trod this road, and Iraqi nongovernmental organizations bring food to some of the estimated 160,000 civilians who have fled the battle of Mosul for refugee camps.
One car flying a white flag drove by with a corpse in the back, transported for burial across the river.
But each civilian vehicle, often packed with people, must pass a strict checkpoint on both sides. The checkpoint stops are tense. Soldiers and militia members ask where the Arab passengers are from and check the cargo. They are looking for Islamic State fighters. A Shiite flag with the sketch of a sword dripping blood flutters on the bridge.
As the road from the Tigris nears Mosul, it merges with a large highway that runs to Baghdad and the presence of the militias appears to thin out. The Iraqi army and Federal Police take the lead at checkpoints. Many vehicles of the Iraqi armed forces display Shiite flags, but the militias are not playing an official role in the battle for the city — only in rural areas around it.
A massive new United Nations camp at Hamam al-Alil is largely unoccupied. A giant sign by the PMU indicates that Shiite militias control access to the camp and claim they are “confirming the [safety]” of the camps and will provide aid equally.
The Shiite militias know that they are viewed by many with suspicion and are accused of discrimination and sectarianism. When a reporter tries to enter an older part of the Hamam al-Alil camp, militia members wearing black balaclavas and masks with skulls on them block the way.
Civilians in these neighborhoods have transitioned from Islamic State rule to another form of religious rule, with militarized checkpoints controlling their movements. A young man who fled one of these villages when the Shiite arrived and now lives in a reformatory in Irbil said the Shiite militias don’t belong in his Sunni village or northern Iraq.
In many ways, civilian life has an air of normalcy — even in Mosul with the sound of gunfire in the background. Women in black abayas wait for food to be distributed. Men stand around smoking, observing. Children play, some with visible burns from the war.
Most of these people have lived with years of war. Since the 1980s and particularly since 2003, they have witnessed rounds of violence. In January 2008, for instance, the city was hit by more than a dozen attacks a day, including improvised explosive devices, car bombs and shootings.
By contrast, life under the Islamic State was relatively peaceful for many pious Sunnis, many of whom greeted the takeover warmly in 2014.
“This too shall pass,” seemed to be the overall feeling in and around Mosul. Saddam came and went, then the Americans, the jihadis, the Americans, the Islamic State and now the Shiite militias. If Shiite militias continue to hoist flags over Sunni mosques in the city and the militias continue to man dozens of checkpoints in the rural countryside, then it is likely only a matter of time before insurgent attacks begin again.