Sharaa, now Syria's de facto leader, said in a BBC interview last month that he would not rule out allowing the Russians to stay, and he described relations between the two countries as "strategic".

Moscow seized on his words, with foreign minister Lavrov agreeing Russia "had much in common with our Syrian friends".

But untangling the ties in a post-Assad future may not be easy.

Rebuilding Syria's military will require either a completely new start or a continued reliance on Russian supplies, which would mean at least some kind of relationship between the two countries, says Turki al-Hassan, a defence analyst and retired Syrian army general.

Syria's military cooperation with Moscow predates the Assad regime, Hassan says. Virtually all the equipment it has was produced by the Soviet Union or Russia, he explains.

"From its inception, the Syrian army has been armed with Eastern Bloc weapons."

Between 1956 and 1991 Syria received some 5,000 tanks, 1,200 fighter aircraft, 70 ships and many other systems and weapons from Moscow worth over $26bn (£21bn), according to Russian estimates.

A lot of this was in support of Syria's wars with Israel, which has largely defined the nation's foreign policy since it gained independence from France in 1946.

More than half of that sum was left unpaid when the Soviet Union collapsed but in 2005 president Putin wrote off 73% of the debt.

For now, Russian officials have taken a conciliatory but cautious approach towards the interim rulers who toppled Russia's long-standing ally.

Vassily Nebenzia, Moscow's UN envoy, said recent events had marked a new phase in the history of what he called "brotherly Syrian people". He said Russia would provide both humanitarian aid and support for reconstruction to allow Syrian refugees to return home.