Beirut — Islamic State (IS) is fighting hard to reinforce its presence in Syria as it loses ground in Iraq, deploying fighters to seize full control of a government-held city in the east while battling enemies on three other fronts.
It underlines the residual strength of IS despite losing a cluster of Iraqi cities and half of Mosul, and indicates the challenges facing US President Donald Trump in the war he vows to wage against the group.
The jihadists have opened their most ferocious assault yet to capture the last Syrian government-controlled area in the eastern province of Deir al-Zor, a pocket of Deir al-Zor city surrounded by IS territory.
The assault has raised fears for tens of thousands of people living under government authority in the city. Their only supply route has been cut off since IS severed the road to the nearby air base last week.
A military commander in the alliance of forces fighting in support of President Bashar al-Assad said IS was seeking to turn Deir al-Zor city into a base of operations.
"They want to take it by force — and right now," said the commander, a non-Syrian who declined to be identified because he is not an official spokesman for the alliance that includes a range of Iranian-backed Shia militias, Lebanon’s Hezbollah, and the Russian air force.
"The situation in Deir al-Zor is very difficult."
IS appears focused on strengthening its hold over a triangle of Syrian territory connecting its main base of operations — Raqqa city — with Palmyra to the southwest and Deir al-Zor to the southeast.
The group seized Palmyra from government forces for a second time in December, a reversal for Assad just eight months after he had retaken control of the city and its world heritage site with the help of the Russian air force.
IS fighters are also putting up stiff resistance against campaigns against them in northern Syria, one by US-backed militias including Kurdish groups, and another by Turkish-backed Syrian rebel groups.
"They are able to fight on four fronts; if they were in a state of great weakness, they would not be able to do this," said Rami Abdulrahman, director of the Syrian Observatory for Human Rights, a UK-based organisation reporting on the war.
A senior commander in the pro-Assad alliance, also a non-Syrian, said: "The strength of Daesh is that it is a cancerous tumour, and when you remove it from one place, it goes to another." The commander urged the US-led alliance and "every air force" to attack IS to stop it moving its convoys in the Deir al-Zor area, an apparent sign of dissatisfaction with the current level of support from the Russian air force there.
Though IS has faced military pressure in Deir al-Zor province, including raids by US special forces, the attacks against it there have been less intense than in other parts of its self-declared caliphate.
Deir al-Zor has been a secondary priority for the Syrian army and its allies, which are most concerned with rebel forces in western Syria.
The US-backed campaign led by Syrian Kurdish groups has focused on encircling and taking Raqqa city.
IS has been asserting itself in Syria with trademark brutality, killing civilians execution-style in Palmyra’s Roman Theatre last week, according to the observatory. IS has also generated headlines by blowing up more of Palmyra’s ancient ruins, with satellite imagery showing on Friday the destruction of one of its most famous monuments.
If Trump follows through on suggestions that he may cooperate with Russia in the fight against IS, eastern Syria would be an obvious target
Russia seized on the capture of Palmyra from IS in 2016 as evidence of its efforts against the group in Syria, after critics accused it of mostly targeting moderate rebels.
There has been no sign of a major effort to take back Palmyra a second time.
If Trump follows through on suggestions that he may cooperate with Russia in the fight against IS, eastern Syria would be an obvious target. However, this would mark a major shift in US policy because it would help Assad. US policy under president Barack Obama was built on the idea that Assad had lost legitimacy. Obama rejected any co-operation with Assad in the fight against IS, describing his rule as part of the problem.
A Syrian official said the US-led coalition was doing nothing to prevent IS from moving its forces into Syria. "This is what’s helping Daesh," the official said.
"After losing Mosul, Daesh will think of reinforcing its capacity in Raqqa and Deir al-Zor because … they don’t have any sanctuary. The final battle will certainly be there."