As ISIS retreats in Syria, the US and Iran scramble for control
BEIRUT — US and Iran-backed forces are locked in a race to take Islamic State strongholds in southeastern Syria and seize a stretch of land that will either cement Tehran’s regional ambitions, or stifle them.
The scramble for pole position in Deir al-Zour province is likely to be one of the most consequential fights against the extremist group in Syria, posing a regional test for President Trump as his administration turns up the rhetoric against Iran.
While the battle for Raqqa, the Islamic State’s most famous Syrian stronghold, is heating up, there are signs that an offensive to seize Deir al-Zour will be tougher, and have greater consequences for the group’s long-term survival as a force holding significant territory.
On the Euphrates River between Raqqa and the Iraqi border, the city of Deir al-Zour is the largest urban center in eastern Syria. Victory for Syrian and Iran-backed forces there would give Tehran control of a large swath of the Syrian-Iraqi border, securing a land route through Iraq and southeast Syria to Damascus in the southwest, and on to its proxy, Hezbollah, in Lebanon.
For the United States, gaining control of Deir al-Zour would give it a bargaining chip for the future and demonstrate to regional allies its willingness to challenge Iran, after Trump promised to roll back the country’s ‘‘rising ambition.’’
‘‘The weakening of ISIS was always going to open a race for territory, dominance, and influence. The aggressive tone coming from Washington incentivizes Iran to speed up its operations,’’ said Emile Hokayem, a Middle East analyst at the International Institute for Strategic Studies. ‘‘The problem is that even what the US sees as limited goals clash with more ambitious Iranian ones.’’
On Tuesday, the United States clashed directly with Iranian proxies for the second time in a month, bombing progovernment militiamen as they advanced on an outpost used by US Special Forces at al-Tanf, a key border crossing near Syria’s southeastern border with Iraq.
The airstrikes have raised fears of retaliation in battle zones such as Iraq, where US and Iran-backed forces are both fighting the Islamic State.
Experts say the Islamic State has moved senior leaders into Deir al-Zour, along with a growing number of foot soldiers, as internationally backed forces move in on Raqqa and Mosul, the group’s so-called capitals in Syria and Iraq.
To reach the province, both sides are moving through Syria’s vast southern desert as they head for the Islamic State-held town of al-Bukamel.
The race for position began last month after Russia, Turkey, and Iran agreed to a cease-fire agreement that covered four parts of the country. Rebel commanders and Western diplomats believe the deal was intended to help President Bashar Assad of Syria and his allies concentrate resources in the east as they struggled to hold ground on multiple fronts.
‘‘We see the link clearly now. Accepting those de-escalation zones meant the regime and its allies were able to relax and move resources,’’ said Abu Waleed, a commander with the US-backed rebel group Usoud al-Sharqiya.
The retaking of the oil-rich Deir al-Zour region could give the Syrian government a financial boost and help diminish Assad’s economic dependence on Iran and Russia, which have bankrolled his fight against a rebellion that began in 2011.
This weekend, the race accelerated as rebel commanders said that US Special Forces had helped them build a new forward operating base about 40 miles northeast of al-Tanf. In photographs circulating on social media, a US flag fluttered in the wind as fighters manned truck-mounted weapons.
The US military said last week that it had bolstered its ‘‘combat power’’ in southern Syria, warning that it viewed Iranian-backed fighters in the area as a threat to nearby coalition troops fighting the Islamic State.
US Army Colonel Ryan Dillon, a spokesman for the US-led coalition in Iraq and Syria, told reporters Thursday that Iranian-backed forces were 20 miles within a ‘‘deconfliction’’ zone they had declared a week earlier in an attempt to de-escalate tensions and holding firm near the US base at al-Tanf.