Many say, often with vehemence, that the current drama is the consequence of ongoing Western inaction and the US retreat at critical moments in an ever more uncontrollable conflict, whose regional dimensions are fast becoming global.
Nobody in the Middle East is counting on US President Barack Obama. The gloomy prediction, of most, is that the war, which has killed at least a quarter of a million people and displaced half the Syrian population, is about to get much, much worse.
The conflict has taken a deadly trajectory throughout. It began as a popular uprising against Mr Assad, part of the Arab Spring, then it became a sectarian war with regional patrons, such as Iran and Saudi Arabia, backing their local proxies.
Military interventions by Russia and Iran have pushed the war to the brink of a full-blown international conflict.
Mr Faisal Al Yafai, chief commentator at the UAE-based newspaper The National recalled the words of General David Petraeus, who led the "surge" of American military reinforcements into Iraq in 2007-08 - "Tell me how this ends".
After the Russian "surge" into Syria, he said: "America and its allies now look like the only group without a plan."
He believes the emerging military alliance between Russia and Mr Assad's other main backers - Iran and Lebanon's Hizbollah - does have an idea of "how this ends". The same is true of ISIS, he said. The end for the Assad family, he argues, is its survival. For ISIS, it is to carve out and consolidate the caliphate it declared in large swathes of Syria and Iraq last year. For Russia and Iran, however, it is "nothing less than the replacement of the US-Israel axis with one of their own".
A NEW AXIS?
With the Kremlin's creation in Baghdad of a centre to share intelligence among Syria, Iraq, Iran and Russia, a Moscow-backed network now runs from Teheran, Baghdad and Damascus, and via Hizbollah, into Lebanon. The new axis is taking shape as the US has withdrawn ground troops from Iraq and is winding down its military presence in Afghanistan.
While it continues to police Gulf waterways from a base in Bahrain and maintains an airforce presence in Qatar and Turkey, Washington appears determined to avoid deeper military entanglements in the Middle East.
Analysts and diplomats say the turning point in Syria came two years ago when Mr Obama and his European allies shied away from responding to the Assad army's alleged nerve gas attacks on civilians in the rebel enclaves east of Damascus - even though the US leader had repeatedly declared that a "red line".
"It was the point when the Assad regime, and mainly the Iranians, realised that the Americans are not serious, that they really didn't care enough," Mr Yafai said.
For that reason, he doubts that Russian intervention will lead to a proxy war in the Middle East with Moscow.
"You have to ask that question in a different way," he said. "What would it take to make the Americans intervene? Would it take children and women being slaughtered? Well, that happened. Will it take millions of people on the move? That happened. Will it take hundreds of thousands of civilians murdered? Well, that happened," he told Reuters. "America wasn't willing, at any point, to intervene, so why now would it suddenly intervene? It is a free field for Mr Putin and the Russians."
Added to US reluctance, the regional scene could not have been more favourable for Iran and Moscow to step in.
Saudi Arabia and its Gulf Sunni allies, the main backers of anti-Assad rebels, are immersed in a war in Yemen against Iranian-supported Houthi rebels, while Turkey is busy with its own Kurdish insurgency. Turkey and its Gulf allies will, most likely, respond to the Russian and Iranian build-ups by increasing military support for mainstream opposition forces in Syria, rather than risk direct intervention.
The Assad government, Syria watchers say, has been lucky with its enemies as well as its allies. What may alter this calculus, some analysts say, is if Russia and Iran move to recapture areas of north-western Syria seized by insurgents earlier this year. It is in that area that Russian jets have targeted not ISIS, but other Islamist rebels who are fighting, with the support from Turkey, Saudi Arabia, Qatar and, in some cases, the US, against both Mr Assad and ISIS.
As Reuters reported last week, Iranian troops and their Hizbollah allies plan to use Russian air cover to launch a ground offensive in Idlib and Hama provinces, where ISIS presence is minimal. That risks turning all Sunni factions against Russia, while Mr Putin is already nervous about the presence of large numbers of Chechens on the ground in Syria and about ISIS ambitions to build up its presence in the northern Caucasus.
Mr Sarkis Naoum, a leading Lebanese commentator on Syria, said if Russia decided to launch a wide-scale operation in the north, it would lead to a "war on an international scale".
If, on the other hand, Iran confined its military role to shoring up and fortifying an Assad-held north-western coastal enclave and the capital, Damascus, and avoided mainstream rebel-held territory close to the Jordanian and Turkish borders, the conflict would probably not escalate much more widely. "This step (attacking rebels in the north) opens the door to an open-ended war in the region and a declared (Sunni-Shi'ite) sectarian war which could, in the long term, transform into a second Afghanistan for the Russians, and they won't be able to win it," Mr Naoum said.
Moscow's critics and non-ISIS rebels say the Russian and Iranian interventions will draw more Sunni foreign fighters and jihadis into Syria. "What will Mr Putin do then?" asked Mr Naoum. "If this battle takes place, then Mr Putin would drag himself and the world into a predicament where the beginning is known, but the end is not."