Part of the foundation for the success of HTS and its allies has been laid over the past four years, with the group investing in professionalizing its forces and buying materiel such as drones, analysts say.

“The expansion of units… along with large-scale indigenous rocket and missile production — has created a force that Assad’s regime has seriously struggled to defend against, let alone outmaneuver,” said Charles Lister, director of the Syria program at the Middle East Institute, a…