Two rebel groups are leading the push. One is Hayat Tahrir al-Sham ( HTS ), which emerged from al-Qaeda’s Syrian affiliate. It cut ties with the jihadist group in 2017 and has since set up a provisional government in rebel-held Idlib province in north-west Syria. The other faction, the Syrian National Army ( SNA ), is a Turkish proxy.

A historian explains why U.S. sanctions and Iran and Russia’s entanglements in other wars helped create an opening for rebel groups to overrun the Syrian Army.

Anti-government fighters are continuing to advance even as Syrian and Russian forces seek to halt their progress.