ERBIL, Iraq — Dynamics affecting armed opposition groups from Syria’s easternmost region, the Islamic State-held Deir ez-Zor, have shifted significantly in recent months.

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.

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.

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.