The recent all-out rebel assault on regime-held west Aleppo was a huge shock, both to the regime fighters entrusted with holding the enclave as well as the hapless residents of that part of the city. The Islamist groups had been mustering their forces for quite some time. The coordinated offensive on several fronts was spearheaded by prominent jihadist groups, most notably the al-Qaeda affiliate Jabhat al-Nusra, and reportedly led by Chechens. It has featured a host of foreign fighters.