The Syrian military has deployed at least one Russian TOS-1 heavy flamethrower system in order to strengthen the defense of the government-held city of Aleppo, according to pro-government sources.
If this is true, the military is actively preparing for possible major attack of Hayat Tahrir al-Sham (formerly Jabhat al-Nusra, the Syrian branch of al-Qaeda) and its allies from the so-called moderate opposition.
The Syrian Arab Army (SAA) is now deeply invoved in a large-scale anti-ISIS operation in central Syria. The goal of the operation is to lift the ISIS siege from the city of Deir Ezzor.
Hayat Tahrir al-Sham may use this for launching an attack against government forces at some front in the province of Aleppo or Hama.