AL QAIM, IRAQ — As the fight against the Islamic State in eastern Syria — where some of the U.S. troops President Donald Trump has promised to withdraw are based — enters its final stages, ISIS fighters are trying to cross into Iraqi territory.

“We normally have daily sightings,” Col. Saleh Al-Yacoubi of the Iraqi border guard said of the ISIS fighters, who are now cornered in a handful of villages on the reeds-enveloped east bank of the Euphrates River. “If they are armed, we hit them with full force.”

For months, the attempted crossings have kept the Iraqi border guards who patrol the area on their toes. But over the past weeks, the situation at the border has become increasingly uncertain, as the U.S. has begun moving military hardware and supplies out of eastern Syria in the wake of Trump’s surprise announcement of a troop withdrawal last month.

Al-Yacoubi spoke at a base north of Al Qaim, about 500 yards from the last ISIS position in Syria. His U.S.-backed forces, together with the Iraqi army, secure this side of the border, working closely with U.S. and French coalition troops stationed nearby. The Popular Mobilization Forces, or PMF, an umbrella group of largely Shiite paramilitary units backed by Iran, meanwhile, patrols the Iraqi border south of Al Qaim. To the west of the border fence, some 2,000 ISIS militants are wedged between the U.S.-backed Kurdish forces to the north and Syrian regime fighters to the south.

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Map: Soohee Cho/The Intercept

The array of armed groups on both sides of the border underscores the breadth of the coalition that has come together to fight ISIS in Iraq and Syria. But it also hints at what could go wrong if the militants take advantage of the impending U.S. withdrawal to stage a comeback.

In Al Qaim, the last Iraqi urban center to be freed from ISIS in November 2017, the Iraqi security forces, which receive air cover, intelligence, and strategic advice from the United States, and the Iranian-backed PMF have long distrusted each other. A cascade of conflicting announcements by Trump and other U.S. officials over the last month have raised concerns about the ripple effects of a premature U.S. withdrawal from Syria. The 2,000 American troops there are expected to leave over the next few weeks, though the precise timing remains unclear.

The pullout “will negatively impact us, 100 percent,” Al-Yacoubi said. “But we are prepared to protect the border, whether the coalition forces are present in Syrian territories or not.”

Al-Yacoubi and his fellow border guards, equipped and trained by the United Sates, monitor ISIS movements around the clock using day and night cameras. When they spot suspected militants, they inform U.S. and French troops, who occasionally launch artillery strikes across the border.

“We don’t allow [ISIS] to cross. We deal with them while they are still inside Syria,” Al-Yacoubi said.

The U.S. troops who work with Al-Yacoubi are equally determined to prevent militants from seeking sanctuary in Iraq’s deserts.

ISIS “will be destroyed and defeated in the [Middle Euphrates River Valley] and they need a place to escape to,” Lt. Col. Kent Park, who is based in Al Qaim with the 3rd Cavalry Regiment, told The Intercept before the withdrawal announcement. “It’s important that we maintain that border security.”

A spokesperson for the U.S. forces in Baghdad declined to comment about the impact of the withdrawal from Syria on operations near the Iraqi border, referring The Intercept to the office of the secretary of defense, which did not respond to a request for comment. In a press conference this week, Iraqi Prime Minister Adel Abdul Mahdi said that Iraq was worried about the withdrawal, and that his government is working with its regional allies, including the Syrian government, to mitigate any negative consequences.

During a Christmas visit to an American air base near Al Qaim, Trump reaffirmed that, despite the Iraqi government claiming victory over ISIS more than a year ago, U.S. troops would remain in the country. One reason for the continuing U.S. presence in Iraq, he said, was “to watch over Iran.”

Trump also told reporters that the U.S. might base more commandos near Al Qaim to conduct special cross-border operations when needed. Several Iraqi officials have since alleged that the U.S. has set up new bases in Iraq, but a U.S. coalition spokesperson denied the claims.

A Popular Mobilisation Forces (PMF) fighter takes his position near the Iraqi-Syrian border in al-Qaim, Iraq, November 25, 2018. Picture taken November 25, 2018.  REUTERS/Alaa al-Marjani - RC1D8A730420

A Popular Mobilization Forces fighter takes his position near the Iraqi-Syrian border in Al Qaim, Iraq on Nov. 25, 2018.

Photo: Alaa al-Marjani/Reuters

Even without more U.S. troops on the border, the proximity of existing coalition forces to PMF fighters could turn Al Qaim into a potential flashpoint in the increasingly tense relationship between the United States and Iran.

The town is sprinkled with checkpoints manned by both the Iraqi army, which works alongside U.S. forces, as well as the PMF. The two organizations are vying for control, with civilians often caught in the middle.

“The presence of these forces is affecting the community,” said Ahmed Al-Dilemi, the mayor of Al Qaim. Both forces claim to control the town, leaving local traders, who need security clearances to bring goods there, unsure of who holds sway. “If the car is approved by the army, the PMF rejects [it], and the other way around, if PMF approves, then the army disapproves,” the mayor said.

Although the PMF has been officially incorporated into Iraq’s security forces, in practice, it operates independently. While regular Iraqi forces criticize the PMF for pursuing its own agenda, the PMF, in turn, regards itself as a bulwark against American influence, sometimes accusing U.S.-backed factions of not standing up to what the PMF regard as an occupying force. (Some locally recruited Sunni PMF units do collaborate with U.S. forces, though they generally wield less power than their Shiite counterparts).

With their common foe on the verge of defeat, the rifts between the U.S.-led coalition and the PMF appear to be deepening. The PMF has been increasing its numbers along the border with Syria, where some of its units also fight alongside Bashar al-Assad’s Syrian government troops.

Among them is Kata’ib Hezbollah, a U.S.-designated terror group and just one of a half-dozen Shia-led PMF units that have set up shop here. A large surveillance balloon hovers over the American base nearby, monitoring the area. The U.S.-led coalition and the PMF have divided areas of control to avoid confrontation, but that hasn’t been enough to calm tensions.

During a tour of PMF areas south of Al Qaim, Ahmed Nasrallah, who commands a PMF unit called Liwa Al Toufuf, rattled off a list of grievances against the Americans: They tried to undermine the PMF’s authority by supporting local Sunni PMF units; they used their surveillance assets to spy on the PMF; and they deliberately targeted PMF positions.

He pointed to a Kata’ib Hezbollah compound nearby that he claimed had been hit by a U.S. airstrike last June (other sources reported that Israel was responsible). The PMF threatened retaliation, but the U.S.-led coalition has denied involvement and rejected the idea that it targets the PMF.

“It’s absolutely false,” said Park, of the U.S. Army. “We have never targeted the PMF. The PMF are considered part of the Iraqi security forces. The rules of engagement prevent us from doing it, and it’s not in our interest to do it.”

Nevertheless, Al Qaim is a strategic point along a corridor that connects Iran to Beirut. The PMF controls more than 200 kilometers of the southern part of the Iraqi border with Syria, offering Tehran plenty of space to secure supply routes to its allies in Syria and Lebanon.

Unlike in the north of Al Qaim, where the coalition has been building a border fence to prevent incursions, there’s no physical barrier along the southern, PMF-controlled border. Instead, PMF outposts adorned with various militia flags line the frontier, in addition to the watch towers of Iraqi border guards.

“This is the second line of defense against ISIS,” Nasrallah said as he pointed toward the outposts. But the PMF doesn’t face ISIS across the border; instead, Syrian regime forces control the area on the other side. “We have good coordination with them,” Nasrallah admitted, though he denied reports that supplies were being sent across.

As the convoy passed through the Kata’ib Hezbollah areas, Nasrallah received a radio call that a sniper had attacked a PMF vehicle near the American base.

“Such attacks only ever come from the direction of the Americans,” Nasrallah claimed. “They do this to destabilize the region, so they can justify their continued presence here.” Two sources within the Iraqi security forces who work alongside American troops independently told The Intercept that the U.S. occasionally fires at the PMF when they are perceived to move into unauthorized areas, though a Western diplomat thought it was more likely that, just like in the case of the Kata’ib Hezbollah compound, Israel was responsible for such incidents.

Nasrallah accused the U.S. forces of aiding ISIS, a widespread but unsubstantiated belief among the PMF that highlights the depth of antagonism between the two sides.

In a bid to prove that the PMF was in charge, he rushed to the scene of the shooting and ordered his forces to search the area. Minutes later, officers of the Iraqi army appeared. The two sides greeted each other warily.

While cordial, the Iraqi army and PMF compete for territorial control and credit for foiling ISIS attacks. On paper, the PMF is supposed to be part of the Iraqi security forces. But Iraqi army officers and politicians often express dismay at the lack of de facto integration on the ground.

“We don’t have any control over [the PMF]. They are outside our chain of command,” said Gen. Adel Molaan of the Iraqi army’s 8th Division.

In the absence of direct communication between the PMF and American troops, the Iraqi army serves as a go-between, passing on information about troop movements to avert clashes. It’s an inefficient arrangement that seems prone to errors and hampers information-sharing about the presence of ISIS militants.

“Anytime you have a battlefield, you want all the different actors and forces to be able to communicate and coordinate,” said Park. “That certainly makes things a lot easier to prevent the enemy from potentially trying to work around the forces that should be on the same side.”

Though ISIS no longer holds ground in Iraq, sleeper cells around Al Qaim still mount guerrilla-style attacks against security forces. According to the U.S.-led coalition, most occur in PMF-controlled territory. Honeycombed with riverbeds and valleys, the area lends itself to insurgent tactics, a factor that is further amplified by the lack of coalition air and artillery support.

Nasrallah denied reports of any ISIS attacks in PMF areas or the need to cooperate with U.S. forces.

“I don’t need the Americans — not their support, not anything else,” the commander said dismissively.