The rapid advance on Aleppo came just four days into a surprise rebel offensive that is the most intense escalation in years in the country’s civil war.

The Hayat Tahrir al-Sham rebel group in Syria has taken control of much of Aleppo city after local forces withdrew to organize a counteroffensive to retake Aleppo.

With Russia and Iran devoting much of their resources to their own wars, the Syrian rebels took Aleppo with little resistance from the Assad regime.