Syrian rebels have swept through parts of the country at lightning pace, taking control of the the second-largest city, Aleppo. But who are they and what are their aims?

Sham, a powerful Syrian rebel faction, has launched offensive in Aleppo by taking military bases and villages from Assad's forces. This marks a significant escalation of the civil war in Syria, with HTS posing a major threat to Assad's regime.

Hayat Tahrir al-Sham (HTS) is a Sunni Islamist political and militant group that was set up in 2011 which has a key role in the Syrian civil war. The leader of the Islamist Group (IS) Abu Bakr al-Baghdadi was involved in the formation of HTS in 2011 under a different name, Jabhat al-Nusra.

The 13-year civil war in Syria has roared back into prominence as insurgents seized Aleppo in a shock offensive marking a major threat to president Bashar al-Assad’s brutal regime.The push – which saw insurgents seize the country’s second-largest city – is among the strongest in years,

The 13-year civil war in Syria has roared back into prominence with a surprise rebel offensive on Aleppo, one of Syria's largest cities and an ancient business hub. The push is among the rebels' strongest in years in a war whose destabilizing effects have rippled far beyond the country's borders.