The missles in Syria wouldn't have an effect if there will be a large scale operation against this country. On the other hand with Russian Navy base there it would be a surprise if Putin leave its ally bare handed against annoying intelligence flights. Low cost and very efficient way to say that Russia finally cares. Bravo Putin!
ISIS claims responsibility for bombing in Baghdad suburb; death toll hits 21 (Reuters)
from the article: Sharon: Russian missiles being sold to Syria do threaten Israel