This week, Syrian government forces have repelled a large ISIS advance in the T2 pumping station area, liberated the key town of Sukhna and further advanced in the area north of the Homs-Palmyra highway.
As a result of these developments, ISIS lost initiative in central Syria and is now in a defensive position in key directions of the government advance.
According to pro-government sources, the ISIS leadership is now steadily withdrawing forces from the area north of the Homs-Palmyra highway. ISIS understands clearly that if government forces overrun the ISIS defense north of Sukhna, they will be able to cut the whole ISIS grouping deployed in the eastern Hama countryside.
This is allegedly one of the man reasons behind the decisdion. The another reason is a lack of manpower to defend the whole central Syria.