Last weekend, Hay'at Tahrir al-Sham (HTS), a former al Qaeda affiliate with a base in northwest Syria, launched a surprise offensive. The rebels captured Syria’s second-largest city, Aleppo, and headed toward Homs and Hama, two major population centers. The weekend’s battles mark the first significant shift of battle lines in Syria since 2020. With Russian and Syrian airstrikes on rebel strongholds picking up, Asher Grant-Sasson speaks with Jon Alterman, director of the CSIS Middle East Program, about the regional and geostrategic implications of a possibly new phase in Syria’s 13-year civil war.