BEIRUT: The battle for Syria’s Aleppo, which is key for both the regime and rebels and the most important so far in a five-year civil war, is likely to be protracted. Both sides have massed troops around the country’s northern second city, which has roughly been divided since 2012 between a regime-held west and a rebel-controlled east. How strong are the rebels? The Army of Conquest — which in 2015 drove the regime out of most of the northwestern province of Idlib — is the main rebel coalition in this battle against forces loyal to President Bashar al-Assad. The alliance includes a dozen groups including the Fateh al-Sham Front — which used to have ties with Al-Qaeda — and the Islamist faction Ahrar al-Sham. According to military experts, the alliance consists of 30,000 to 40,000 well-trained and motivated fighters including around 10,000 in Aleppo province. Among them are several thousand foreign jihadists.