Hundreds of fighters from Iran -backed Iraqi militias have crossed into Syria to help the regime of Bashar al-Assad fight off an insurgency across much of the northwest of the country, which has seen the seizure of the second city of Aleppo.

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.

“Syria is forging ahead in combatting terrorism with force and resoluteness on the entirety of its territories,” Assad said in a statement. The Syrian army bombed rebel positions in Aleppo and has dispatched reinforcements to the area north of the city of Hama to try to stop the advance.

Time and time again the Assad dynasty has survived internal and external challenges and lived to fight another day. But nothing lasts forever.