Iran-backed militias entered Syria overnight to support President Bashar al Assad's fight against a rebel uprising, according to army sources. The White Helmets say at least 25 people have been killed in northwestern Syria in airstrikes carried out by the Syrian government and Russia.

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.

Syrian rebel fighters are advancing southward after capturing much of Aleppo, Syria’s largest city, posing the most serious challenge to President Bashar al-Assad in years amid the country’s civil war,