The Syrian rebel group Hayat Tahrir al-Sham (HTS), which seized Aleppo in a shock offensive over the weekend, is an Islamist movement that has long ruled swathes of the country's northwest.

A major offensive has seen rebel groups in Syria retake the country’s second city, Aleppo – and demonstrated the growing prominence of the Islamist group Hayat Tahrir al-Sham in the 13-year-long civil war.

Syria’s civil war has exploded back onto the world stage after insurgents poured out of their main bastion in northwestern Syria and seized large parts of nearby Aleppo, Syria’s largest city, and doze