Who are the rebels who have seized control of Aleppo, Syria?

The group behind these dramatic developments, Hayat Tahrir al-Sham (HTS), has held a consequential but checkered role in the country’s long-running civil war.

An Islamist group that the US and several other nations long ago designated a terrorist organization, it was known as Jabhat al-Nusra when it formed a formal alliance with Al-Qaida more than a decade ago.

But in recent years HTS has publicly disavowed international terrorism and tries to present a more moderate face, according to Charles Lister, the director of the Syria Program at the Middle East Institute think tank in Washington D.C.

Another significant evolution for HTS is its decision to collaborate with other armed Syrian factions, against which it might previously have fought, says Lina Khatib, an associate fellow in the Middle East and North Africa program at Chatham House.

Read more: NPR