Syrian rebel forces led by Hayat Tahrir al-Sham, or HTS, declared they had ousted President Bashar al-Assad and he had fled Damascus on Sunday. But what is HTS, and how did it rock the long-simmering tensions in Syria? HTS is a Sunni Islamist militant and political group that traces its roots to the beginning of the Syrian civil war.

Standing before a cheering crowd in Damascus’ historic Umayyad Mosque, the broad and bearded Abu Mohammad al-Jolani declared a new chapter in Syria’s history.

Rebels in Syria, led by the Islamist alliance Hayat Tahrir al-Sham, or HTS, have captured Damascus, about a week after taking over Aleppo and Hama, and ousted President Bashar al-Assad. As this dramatic shift in the ongoing conflict continues to unfold,

Syria's main rebel group, Hayat Tahrir al-Sham (HTS), said they are working on taking complete control of the Syrian capital Damascus and promised a new government would take over immediately after its formation.

Jolani, a key figure in the Syrian rebellion, has played a crucial role in planning the recent offensive, leading to significant rebel gains, including the capture of Aleppo and Idlib, as the leader of Hayat Tahrir al-Sham (HTS).

Jolani, the rebel leader who led the Hayat Tahrir al-Shams (HTS) group that took over Syria and collapsed President Bashar al-Assad's regime. CBS News' Courtney Kealy breaks down what's known about Jolani.