The sources told Reuters that Hezbollah had not yet been asked to intervene, adding that the group was not ready to send forces to Syria at this stage following more than a year of hostilities against the Israeli military, including two months of heavy ground fighting in southern Lebanon.

The loss of Aleppo to Islamist rebels represents a stunning defeat for the Syrian regime, highlighting its dependence on enfeebled allies.

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