Jaish Usud al-Sharqiya receives support from the Amman-based Military Operations Center and has in recent months focused on fighting regime-allied forces after long concentrating on the battle against the Islamic State (IS).

The group, made up mostly of fighters and commanders from Deir ez-Zor, has struggled to advance in recent weeks but has managed to advance in some areas such as Bir Mahroutha in the south, where it reportedly seized a tank and weapons from the regime and allied forces Aug. 1 with the help of a local opposition group, the Forces of Martyr Ahmad al-Abdo.

In the southern desert, Jaish Usud al-Sharqiya (Lions of the East Army) made vast gains in the first few months of the year but lost territory after being cut off by the regime and allied foreign, Iranian-backed, Shiite militias and prevented from further advancing into IS-held areas.

Though some of the groups deployed north and south of the region are helping Kurdish fighters retake Raqqa, most are strongly against involvement by the Kurdish-led Syrian Democratic Forces (SDF) in their home region. The importance of using local forces in the fight to retake Syria’s easternmost region has long been seen as key to preventing backlash from the local Sunni Arab population, ethnic-based violations and land grabs.

The group has forces near al-Tanf military base, where US special forces are stationed alongside British and Norwegian ones acting as military trainers for fighters from Maghawir al-Thawra (Revolutionary Commandos Army, or MaT), another group from the Deir ez-Zor region.

MaT fights exclusively against IS unless it comes under attack from other groups as part of its agreement with the Pentagon in exchange for the support MaT receives.

A former member of the MaT communications team told Al-Monitor at a meeting in Turkey on condition of anonymity that a more powerful Pentagon and a weaker CIA as wanted by the Trump administration since it came into office in January has led to greater support for MaT from the United States and lesser for Jaish Usud al-Sharqiya, despite the latter's holding more territory, and that this trend seems likely to continue.

Jaish Usud al-Sharqiya spokesman Badreddin al-Salama agreed, telling Al-Monitor in an interview in southern Turkey in late July that relations between his group and MaT “are in relation to those between the CIA and the Pentagon.”

“We have fought against IS a few times in collaboration with MaT, but that is all,” he added, noting that “we could do so much more if we had air support.”

Salama said, “We could send thousands more men” originally from eastern Syria to join the fight in southern Syria if they could get the necessary permission from the Turkish and Jordanian authorities.

The only way to get the men to Jordan and then through the border into Syria is to enable them to cross into Turkey from northern Syria and then fly them to Amman; otherwise, it would require crossing IS or regime territory, he said.

A small part of Jaish Usud al-Sharqiya has also been stranded in a besieged area of Qalamoun near the Lebanese border for several months.

There are “about 100 fighters” there, Salama said, adding that “a ‘reconciliation deal’ has been proposed by the Russians” that is likely to be accepted but has not yet been.

Meanwhile, the Syrian Elite Forces, a group based in the northern area under Kurdish control whose leaders and core are also Arabs from the Deir ez-Zor region, withdrew from fighting alongside the SDF on the front lines of Raqqa in July. In December 2016, Col. John Dorrian described the group as a “notable” force when he was spokesman for the US-led Operation Inherent Resolve.

The fighters' commander, Abu Saleh, told Al-Monitor in an interview in Erbil in early August that the decision to withdraw from the battle for Raqqa was made after the SDF “continually put pressure on us to come under their direct control and prevented necessary supplies from reaching us.”

He said the SDF had also repeatedly partially withdrawn during battles, leaving some of his fighters exposed.

Abu Saleh is from the Shaitat tribe, which rose up against IS in the oil-rich area in the eastern part of the country and suffered a major massacre at IS hands — at least 1,000 mostly young men were killed in only a few days in August 2014. Prior to this, he was also the head of a local armed group fighting against the regime.

Now, he says, the over 1,000 men he commands have withdrawn to the south of Hasakah. They are not trying to advance and will not do so until they get direct support from the international coalition not channeled through the SDF, he said, adding that this is unlikely to occur until after Raqqa has been retaken, if at all.

The leaders of the groups working in the north and south are in contact with each other “at a personal level,” they all say. Plans to gather all groups whose cores and command structures are from Deir ez-Zor under one umbrella group have been frequently discussed for years, but nothing has come of it yet.

Abu Saleh has lost the optimism he had even a few months back, he told Al-Monitor, adding that he believes the only option for opposition forces to regain Deir ez-Zor would be from the north, given the heavy presence of Iranian-backed militias in the Syrian desert to the south. The regime is also advancing toward Deir ez-Zor from the north.

Several members of various groups from Deir ez-Zor and locals who recently escaped IS-held territory told Al-Monitor they reject out of hand the idea of Kurds being involved in the fight to retake the region, with some saying they would “fight on the side of IS before letting Kurds into the territory.”

Though he feels this attitude is counterproductive, Abu Saleh agrees that the Kurds should not be allowed to take part in the battle. Advancing from the north would necessarily require using Kurdish-held land at least as a staging ground for the operation.

Though some analysts say the Russian-backed Syrian regime and Iranian-backed militias are likely to retake Deir ez-Zor, all of the armed groups Al-Monitor spoke to originally from the region oppose the idea. The United States and others in the international anti-IS coalition would also be averse to the oft-predicted direct supply line from Iran through Iraq, Syria and Lebanon to the Mediterranean Sea that would result.

Supporting local opposition groups such as Jaish Usud al-Sharqiya, MaT and the SEF may be the only real way to prevent this.