AMMAN: US-backed rebels captured portions of a strategic highway from the Islamic State (IS) in the mountains northeast of Damascus this week, part of a military campaign to “limit IS influence” in the country’s southern desert region, a rebel commander told Syria Direct.

Last week, fighters with the Martyr Ahmad al-Abdo Brigade and Jaish Usud a-Sharqia, two Free Syrian Army units which almost exclusively fight IS, launched a westward military offensive from positions in eastern Homs to capture the Damascus-Baghdad (M2) highway.

The M2 runs through the sparsely populated East Qalamoun mountains, IS’s gateway to southern Syria from its strongholds in the country’s northeast, currently under attack by a US-backed military campaign.

The rebels have now broken a months-long siege, imposed by both the Islamic State and regime forces, of the opposition-held city of al-Dumayr, located at the western end of the East Qalamoun mountains. Rebel fighters are currently advancing north from the highway in order to push IS fighters deeper into the mountains, but rebels have not solidified control of the recently acquired territory. (See map inlay.)

“We can’t say that we’ve broken the siege in East Qalamoun for good,” spokesman Said Saif of the Forces of the Martyr Ahmad al-Abdo told Syria Direct. “The Islamic State has several axes from which to launch an attack at any moment.”

A November 4 statement by the Southern Front, the Free Syrian Army and the Martyr Ahmad al-Abdo Brigade announced the capture of three military positions from the Islamic State along the M2 highway.

Opposition forces and Islamic State fighters have clashed in the mountainous region since 2012, said rebel spokesman Saif.

Territorial control in the region has changed hands frequently over the past four years due to the rugged terrain and the large scale of the battlefield.

“Our priorities are clear,” Ahmad al-Tamer, a Martyr Ahmad al-Abdo troop leader, told Syria Direct on Tuesday regarding the latest campaign. “The strategy is to break the Islamic State down, regain the territory under their control in East Qalamoun, and limit their influence in the [eastern] desert region.”

The sparsely populated East Qalamoun region and adjacent desert provide IS with access routes to Bir al-Qasab, its main fortification in the south, and the Lajat region, from which the group, rebels say, smuggle weapons to its affiliates in nearby Daraa and plan and launch suicide attacks against rebel positions.

Although maps show Bir al-Qasab to be encircled by both rebel and regime territory, the desert region’s rough terrain, and the large distances separating inhabited settlements, mean that the group can easily smuggle weapons and fighters in and out of the pockets.

In April, the Islamic State claimed it shot down a Syrian Air Force plane flying over Bir al-Qasab, roughly 75km east of Damascus. Russian-owned news agency Sputnik International refuted the allegation, claiming the crash resulted from technical failures.

Bir al-Qasab is also considered the launching ground for attacks on the Jordan-Syria border, namely the Rukban refugee camp, home to an estimated 75,000 displaced Syrians and the site of at least one recent IS suicide bombing that killed seven Jordanian soldiers.