This is the only port the Russians have in the mediterannean. Here are a couple of articles that explain Russia's interest in Tartus.
Russia set to build up its naval facilities in Syria | Ria Novosti | Jul 20 2009
Russian Navy to base warships at Syrian port after 2012 | Ria Novosti | Aug 02 2010According to the Russian Navy, the naval base in Syria significantly boosts Russia's operational capability in the region because the warships based there are capable of reaching the Red Sea through the Suez Canal and the Atlantic through the Strait of Gibraltar in a matter of days.
However, cypok & you make me rethink this rationale for Russia to support the Syrian regime. As a secondary reason maybe but no more."Tartus will be developed as a naval base. The first stage of development and modernization will be completed in 2012," Adm. Vladimir Vysotsky said, adding it could then serve as a base for guided-missile cruisers and even aircraft carriers.
According to Navy experts, the facility is being renovated to serve as a foothold for a permanent Russian naval presence in the Mediterranean.
Romania & Bulgaria (shared).
Tartus has been very low key for the Russians until recently.