Syrian opposition forces have taken control of much of the country’s second largest city Aleppo, according to residents in the city and video verified by CNN. A rebel alliance launched a surprise attack this week,

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.

Rebel forces opposing President Bashar al-Assad have launched their biggest offensive in years this week, controlling a majority of Syria's second city of Aleppo according to a monitor.