It would most likely be a defensive war by Syria. Look to Iraq as a model. You will be sucked into a war of attrition. You will also be attacking well defended positions. Their missiles will be dispersed, and missile attacks against Israel will begin immediately. You had better have enough of shelters for civilians. You will need them! I almost forgot! You will also see foreign fighters volunteering to defend Syrian sovereignty.
Monitor: Airstrikes hit Islamic State stronghold in Syria, killing at least 13 (Reuters)
from the article: Leaving the home front out of range