In this June 8, 2018 file photo, Iraqi Popular Mobilization Forces march as they hold their flag and posters of Iraqi and Iranian Shiites spiritual leaders during "al-Quds" or Jerusalem Day, in Baghdad, Iraq.

In this June 8, 2018 file photo, Iraqi Popular Mobilization Forces march as they hold their flag and posters of Iraqi and Iranian Shiites spiritual leaders during "al-Quds" or Jerusalem Day, in Baghdad, Iraq. AP Photo/Hadi Mizban, File

The Flash Point Between America and Iran Could Be Iraq's Militias

U.S. troops and Iran-backed fighters had an alliance of sorts in the anti-ISIS campaign. With Washington and Tehran at odds, could they turn on each other?

All the Americans could do was shake their heads as a Shiite militia flag waved above their base.

The troops from the U.S. Army’s 101st Airborne Division were still getting used to living alongside an old enemy. It was the fall of 2016, the start of a U.S.-backed offensive to retake the Islamic State stronghold of Mosul. Some Americans who’d come to aid the effort had also fought in the Iraq War, when the U.S. military suffered hundreds of deaths in battles with Shiite militia groups. Five years after that war ended, they found themselves at an airfield south of Mosul, where the Airborne was stationed in one section, and a militia outpost sat in another. Concrete blast walls separated the two sides. But someone had climbed a radio tower overlooking the U.S. barracks and tied a militia flag to its peak.

An American soldier pointed out the flag one morning with a wry look that suggested he appreciated the troll.

The global fight against ISIS created strange alliances—and the de facto one between the U.S. military and Iraq’s Shiite militias, some of whom are backed by Iran, was among the most striking.

Related: US Official: We May Cut Support for Iraq If New Government Seats Pro-Iran Politicians

Related: Trump’s Latest Warning to Iran Didn’t Come out of Nowhere

Related: ISIS Never Went Away in Iraq

While the two sides had a shared interest in defeating the Sunni extremist group, the alliance was never going to be enduring, and there was always the risk that if tensions between America and Iran ever ignited, the militias could be a flash point.

Those tensions have now spiked.

On Sunday, National Security Adviser John Bolton decision to walk away from the agreement. (The White House on Wednesday introduced a new set of sanctions against Iran’s metals sector.)

Though U.S. officials have so far been vague about the nature of the threat, Phillip Smyth, an expert on Shiite militia groups, told me he takes the risk they pose to U.S. forces seriously. The militia groups that act as Iranian proxies in Iraq, he said, would be an effective tool for further escalation—and for reviving an old narrative that casts U.S. troops as an occupying force in the country.

“Now that [ISIS] is more dislodged and not anywhere near its 2015 state, the narrative of ‘opposing a resisting force’ makes more sense from the Iranians’ ideological and political perspectives,” said Smyth, who is a fellow at the Washington Institute for Near East Policy.

Some Iran-backed militias have made open threats against U.S. forces in recent years, Smyth said. Because of the Trump administration’s aggressive sanctions against Iran, he added, “the threats take on a new and possibly more dangerous trend.”

United under the umbrella of the Popular Mobilization Forces and an official part of the Iraqi security forces, a constellation of Shiite militia groups emerged in 2014 in response to the Iraqi military’s capitulation to ISIS, recruiting thousands of new fighters. Some militia groups are seen as Iranian proxies and have been trained by Iran’s Islamic Revolutionary Guard Corps, while others oppose Iranian influence and bill themselves as Iraqi nationalists. Kata’ib Hezbollah, Asa’ib Ahl al-Haq, and Kata’ib Sayyid al-Shuhada, Smyth noted, are among those in the former category that U.S. officials may be watching closely.

In a 2017 predicted that the Iraqi parliament would eventually vote to expel U.S. troops from the country — and said that if they didn’t leave, they could be driven out “by force.”

The Shiite militias played a key role in the fight against ISIS, such as when they helped recapture the city of Tikrit in 2015, and suffered heavy losses. But they also claimed credit for victories largely won by government troops, and were outpaced similar accusations against other forces. During the Mosul offensive, civilians regularly listed the militias among their foremost concerns in Sunni-majority areas freed from ISIS.

During the anti-ISIS campaign, U.S. military planners were wary of inadvertently providing air cover for the militias when they advanced in concert with the Iraqi army, worried about aiding forces that worked so closely with Iran. Islamic Revolutionary Guard Corps advisers were often on the front lines with the militia groups they supported, and Qassem Soleimani, the commander of the IRGC’s elite Quds Force, was occasionally photographed on the battlefield. (This wasn’t the first time the U.S. military found itself in an unlikely alliance in Iraq: During the Iraq War, it teamed up with some hard-line Sunni groups as part of its campaign to defeat al-Qaeda in Iraq, ISIS’s predecessor.)

Even before the warship move, the Trump administration had designated the IRGC a terrorist group, prompting the Iranians to respond by declaring U.S. forces in the region a terrorist group too. Yet 5,000 U.S. troops remain in Iraq, in close proximity to Iran-backed forces.

After Bolton’s announcement, I spoke with U.S. military officers who served in the country during the fight against ISIS, and they made two points. The first is that the risk the militias pose to U.S. troops in Iraq has been there since the anti-ISIS campaign began in 2014—and so, in a sense, the threats U.S. officials are discussing are nothing new. The second is that while they considered the threats to be manageable, they were real causes for concern.

“The Shiite militias definitely kept some of us up at night,” one officer, who has since retired from the military, told me, recalling the feeling of living and working around the groups even as some continued with “very clear anti-U.S. rhetoric.”

“They were a wild card that we always had to keep an eye on.”

Another recently retired officer noted an instance in which he suspected that U.S. troops already had been targeted by militias: A roadside bomb killed a U.S. service member in October 2017, an incident for which the U.S. military has not assigned blame. Last year, the State Department evacuated the U.S. consulate in the Iraqi city of Basra, citing attacks by Iran-backed militias. “That’s always been there,” he said. “When I hear [U.S. claims of new threats], I’m like, ‘Really, there’s a new threat from Iran-backed militia?’ I remember back in 2004 when we were fighting Iran-backed militias in Iraq. It’s an existing threat that’s been there for years, but it’s up to Iran to dial it up or dial it down depending on the political end state they want to achieve.”

Both of these sources requested anonymity to avoid jeopardizing continued work with the U.S. government, as did a third officer, who remains with the military.

This officer, who also served during the Iraq War, said returning to the country for the anti-ISIS fight and finding himself posted beside Shiite militias was alarming at first—“but as we got to live together, not as much.”

With the ISIS war winding down, though, the two sides no longer have a common enemy. “That dynamic of a co-enemy has changed, and the power of the Shia militia groups has changed as well,” he told me, as militia-allied candidates made surprising gains in last year’s Iraqi elections.

Colonel Scott Rawlinson, a U.S. military spokesman, declined to comment on whether Shiite militias pose a risk to U.S. troops in Iraq, but he stressed that the threat from ISIS remains. The group “has lost its territorial caliphate but has transitioned into a disaggregated network of sleeper cells with the goal of resurging through intimidation and attacks on civilians, community leaders, and security forces,” he said.

The fact that U.S. troops in Iraq and Syria remain heavily engaged in the fight against ISIS underscores the risks of a U.S. strategy in the region that seeks to pivot to a new enemy, in Iran, even as the battle with the old one remains a work in progress.

And as the past few days have shown, both the United States and Iran have levers with which they can escalate tensions.

“Just like the U.S. maintains and refreshes planning for a variety of contingencies, so does Iran. This dynamic—of increasing U.S. pressure and Iranian countermoves amidst mistrust and imperfect information—increases the risk of miscalculation,” Eric Brewer, a former senior official on the Trump administration’s National Security Council who is now a fellow at the Center for a New American Security, told me.

“We are entering a somewhat more dangerous and escalatory period. Those of us watching this have been warning that the administration’s maximum-pressure campaign was—at some point—going to generate an Iranian response.”