U.S.-backed forces announce anti-IS push in east Syria

BEIRUT — U.S.-backed forces in Syria announced a fresh offensive around the Islamic State group’s most important remaining stronghold Saturday, accelerating a global scramble for control of the country’s oil-rich east.

IS militants are under pressure from all sides in the border province of Deir al-Zour, facing down competing offensives involving almost all of the six-year war’s major players, as the extremist group’s self-declared caliphate crumbles across Syria and Iraq.

The Syrian Democratic Forces, a Kurdish-dominated militia supported by U.S.-led coalition airstrikes, said Saturday that it would clear the Islamist militants from territory east of the EuphratesRiver.

“We at the military council decided to start this decisive operation,” said Abu Khawlah, a spokesman for the militia. Dubbed “Operation Jazeera Storm,” the offensive will take place in the Khabur River valley, the coalition said in a separate statement, adding that it planned to hand over the area to a civilian council.

“The morale of our forces is strong, and we are ready for victory,” Mr. Khawlah said.

But in one of Syria’s most complex battlefields, that achievement is far from assured. Government forces backed by Russian warplanes and Lebanese militia reached Deir alZour city last week, lifting an almost three-year IS siege and boosting President Bashar Assad’s argument that his forces should retake the country’s final IS-held pockets.

According to the Syrian Observatory for Human Rights monitoring group, pro-government troops continued their advance Saturday, shelling IS positions while Russian planes launched bombing raids.

In Damascus, Syria’s foreign ministry said the advance “foreshadowed the end of terrorism.”

With SDF forces in control of more than 65 percent of the IS de facto Syrian capital, Raqqa, and most of the militant group’s Iraqi strongholds recaptured, Deir al-Zour province has become IS’s most important refuge.

Leadership figures are understood to have been sighted in its southern cities of Mayadin and Bukamal, among them the group’s most senior leader, Abu Bakr al-Baghdadi.

Although U.S. officials have insisted that they do not anticipate clashes with the Syrian-backed force, the growing complexity of the battleground could make unintended flash points more likely.

A foothold in Deir alZour province would provide Washington with an opportunity to block Iranian expansionism in a strategically important area along the Iraqi border. Victory for the Iran-backed force, meanwhile, would strengthen what has effectively become an unbroken line of control running east from its Lebanese proxies Hezbollah through Syria, Iraq and Iran.

It would also provide the Assadgovernment with a vital economic lifeline, as the province is rich in oil wealth. Six years of war have caused $226 billion in losses, according to the World Bank, leaving the state dependent on credit linesfrom Russia and Iran.