Historicly, it only acted out of despair, just as bear dos when cornered. I believe it will back away of the western forces will mobilize a flotila with in days the Syrian shore needs to be blocked, and its sky's patrolled. Russian cargo must be stopped from beeing unloaded, or destroyed on the ground the second it hits the ground. At the same time there must be an economic pressure, Russia will not act as a result. Historically it only acts out of despair, till then the moral of its people is always low.
Labor court orders Jerusalem light rail operators to return to work (Haaretz)
from the article: U.S. warns Russian missiles may embolden Syria's Assad, prolong conflict