in 2011 with protests against four decades of Assad family rule. In the ensuing civil war a quarter of a million people have been killed and 11 million — half the total population — driven from their homes. Tens of thousands of Syrian refugees have fled to Europe in the past month alone.

Russia says the U.S.-led air strikes against IS positions in Syria are unlikely to be successful and it has called for an international dialogue with Assad.

"In Russia's estimation, Assad's days are not numbered," said Ebtisam Al Ketbi, head of Emirates Policy Center in the UAE. "It wants to obstruct any Arab effort to bring Assad down."

Syria is of vital strategic importance for Moscow. Its naval base at Tartus is its sole installation in the Mediterranean andunderpins its regional influence. The Assad family has also historically been one of Russia's best clients for arms sales.

For many Gulf Arabs, Russia's entry into Syria's war brings echoes of older strains surrounding the Saudi-backed resistance to Soviet occupation troops in Afghanistan in the 1980s.

Some find it ironic that Russia, once a fierce critic of outside intervention in Syria, is now doing just that.

"Has Russia jumped feet first into the meat-grinder that is Syria?" tweeted Mohammed al-Rashed, a Saudi commentator.

"Did it not learn its lesson from Afghanistan, which ripped apart the Soviet Union? Or Chechnya, which crushed Russian arrogance? Did Putin learn a thing?"

Lack of US engagement

Some Gulf Arab officials say the Russian intervention was made possible only by what they see as a lack of U.S. engagement