Jon,

I too would be interested in more background. In the meantime...

Syria is used to the slings and arrows of friends and enemies, by Robert Fisk Wednesday 01 February 2012, The Independent

True, the Syrian regime has never confronted opposition on such a scale. If the fatalities do not yet come close to the 10 or 20 thousand dead of the 1982 Hama uprising, which old Hafez al-Assad crushed with his customary ruthlessness, the widespread nature of today's rebellion, the defections from the Syrian army, the loss of all but one Arab ally – little Lebanon, of course – and the slow growth of a civil war make this the most dangerous moment in Syria's post-independence history. How can Bashar al-Assad hang on?

Well, there's Russia, of course, and the Putin-Medvedev determination not to be caught out by the West at the United Nations as they were when they failed to oppose the no-fly zones over Libya that led directly to Gaddafi's collapse. And there's Iran, for which Syria remains the Arab bridgehead. And Iranian suspicion that Syria is under international attack principally because of this alliance may well be correct. Strike down Baathist Syria and its Alawi-Shia President, and you cut deep into the soul of Iran itself. And there's Israel, which utters scarcely a word about Syria because it fears that a far more intransigent regime might take its place.
Tartus, Syria by wikipedia

Tartus hosts a Soviet-era naval supply and maintenance base, under a 1971 agreement with Syria, which is still staffed by Russian naval personnel. The base was established during the Cold War to support the Soviet Navy fleet in the Mediterranean Sea.[7] During the 1970s, similar support points were located in Egypt and Latakia, Syria. In 1977, the Egyptian support bases at Alexandria and Mersa Matruh were evacuated and the ships and property were transferred to Tartus, where the naval support base was transformed into the 229th Naval and Estuary Vessel Support Division. Seven years later, the Tartus support point was upgraded to the 720th Logistics Support Point.[8]

In 1991, the Soviet Union collapsed and its Mediterranean fleet, the 5th Mediterranean Squadron which was composed of ships from the Northern Fleet and the Black Sea Fleet, ceased its existence. Since then, there have been occasional expeditions by Russian Navy vessels and submarines to the Mediterranean Sea. The naval logistics support base in Syria is now part of the Black Sea Fleet. It consists of three floating docks of which one is operational, a floating workshop, storage facilities, barracks and other facilities.[8]

Since Russia forgave Syria of three quarters, or $9.6 billion, of its $13.4 billion Soviet-era debt and became its main arms supplier in 2006, Russia and Syria have conducted talks about allowing Russia to develop and enlarge its naval base, so that Russia can strengthen its naval presence in the Mediterranean.[9] Amid Russia's deteriorating relations with the West, because of the 2008 South Ossetia War‎ and plans to deploy a US missile defense shield in Poland, President Assad agreed to the port’s conversion into a permanent Middle East base for Russia’s nuclear-armed warships.[10][11] Since 2009, Russia has been renovating the Tartus naval base and dredging the port to allow access for its larger naval vessels.[12]
People's Republic of China–Iran relations and People's Republic of China–Syria relations by wikipedia