In just a few days, a patchwork of rebel forces has seized control of a broad stretch of land in the west and northwest of Syria. But it’s unclear just how much support Syria’s weakened allies can provide.

The Syrian government is denying reports that rebel fighters are advancing in Hama after taking over most of Aleppo province.

Hayat Tahrir al-Sham (HTS) is a Sunni Islamist political and militant group that was set up in 2011 which has a key role in the Syrian civil war. The leader of the Islamist Group (IS) Abu Bakr al-Baghdadi was involved in the formation of HTS in 2011 under a different name, Jabhat al-Nusra.

Over the course of a few days, opposition fighters are now in control of Aleppo and have pushed into several towns in the countryside near Syria's fourth largest city, Hama. Damascus is concerned - President Assad has vowed to defeat the operation.