Iran, Syria's key ally, cannot afford to have the regime of President Bashar Assad fall and is seeking to exploit the political upheaval gripping the Arab world to take the heat off Damascus.
Assad's regime, backed by Syria's military and the vast, all-pervasive intelligence apparatus, has contained nationwide protests demanding its downfall through brutal repression and kept them out the capital and Aleppo, Syria's second city.
But despite the regime's overwhelming firepower it hasn't been able to break the opposition, and as fatalities mount -- at least 1,300, according to human rights groups -- the wider the protests become.
On the other side, the uprising hasn't been able to bring down the Baathist regime dominated by the Muslim Alawite minority.
But recent reports indicate that mutinous troops are turning on the regime and inflicting serious casualties for the first time since the insurrection began March 15.
The regime claimed 120 troops and security men were killed Tuesday by "armed gangs" in the northwestern, predominantly Sunni, town of Jisr al-Shughour.
This is likely to trigger harsher repression by the regime as its clan-based core dwindles. There are fears that civil war may erupt if the army splinters.
There is also a growing sense in the region that the regime's days are numbered. Turkey, one of Syria closest allies, has warned Assad that time is running out and urged him to step down.
The region's political upheaval has already toppled President Hosni Mubarak of Egypt and President Zine el-Abidine Ben Ali of Tunisia.
President Ali Abdullah Saleh of Yemen was flown to Saudi Arabia for treatment after he was seriously wounded Friday in what appears to have been an assassination attempt. He may not return.
In Libya, Moammar Gadhafi is fighting for his life in a civil war triggered by an uprising against him, and is increasingly expected to be fall.
Now the Assad dynasty, which has ruled Syria for four decades with a rod of iron, is facing its gravest threat.
"This chill moment," as the regime threatens retribution for the reported bloodbath at Jisr al-Shughour, "is reminiscent of the day in July 1995 Serbian forces brushed aside U.N. peacekeepers and seized the besieged Bosnian town of Srebrenica," commentator Simon Tisdall observed in British's Guardian daily.
"Europe held its breath, fearing the worst. What transpired was even more awful than most could have imagined.
"Assad should know by now that violence added to violence is not the answer. Amazingly, he does not. Or perhaps he is no longer in control … The risk of civil war now looms large over Syria," Tisdall wrote.
There is a danger, too, that Damascus will seek revenge against Western opponents in Lebanon, through its proxy Hezbollah, and by unleashing Palestinians against Israel, as it has done twice in recent weeks.
It could stir up trouble too in neighboring Iraq, as it has in the past. Iraq, always volatile, is even more vulnerable than usual because of the U.S. military withdrawal scheduled to be completed by December.
However, it's Iran, seeking to take advantage of the Arab Spring to torment and destabilize its Arab rivals such as Saudi Arabia, that may be the greater threat.
Tehran has accused Riyadh of being behind the attack on Saleh in his capital Sanaa that left him and his chief aides seriously wounded.
Whether that's true -- and Riyadh wants Saleh to step down before Yemen, on its doorstep, erupts in civil war as well -- it will resonate in the Arab world and deepen fears that times are going to get tougher.
The Iranians could stir up trouble with Yemen's rebellious al-Houthi tribesmen in the north, as Saudi Arabia says they've done in the past.
Tehran's announcement it has deployed two submarines in the Red Sea on Yemen's west coast has stirred alarm.
"Iran's goal is to project its military and political influence across a weak, restless Arab world, and to protect its repressive brother-in-arms, Syria, from Western interference, military or otherwise," Tisdall commented.