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.

Syrian opposition fighters have launched a lightning offensive, capturing most of Aleppo and arriving as far south as Hama in a matter of days as government forces retreated. The rebels’ rapid gains – the most significant since 2016 – have thrust Syria’s various opposition factions back into the spotlight.