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

The Syrian army said on Saturday dozens of its soldiers had been killed in a major attack led by Islamist Hayat Tahrir al-Sham rebels who swept into the city of Aleppo, forcing the army to redeploy in the biggest challenge to President Bashar al-Assad in years.

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