THE tipping point in Syria is now upon us, accelerated largely by one factor: chemical weapons. Indeed, the crisis in Syria is so rapidly spinning out of control that it is going beyond a tipping point to an escalation point.
An international sense of panic was sparked two weeks ago by the defection of Syria's ambassador to Iraq, Nawaf Fares. Fares, a regime insider, warned that Bashar al-Assad was a "cornered, wounded wolf" who would not hesitate to use the country's stockpile of chemical weapons "if the circle of the people of Syria becomes tighter on the regime".
What this time last week was a brutal civil war is now a ticking bomb, with Israel, Syria's neighbour, saying it is prepared to launch a military operation in Syria, which would dramatically escalate the conflict. Israel's involvement would be triggered by evidence that the crumbling regime is moving any of its stockpile of chemical weapons towards Lebanon.
This is a red line for Israel - it will not allow these weapons to be transferred to Hezbollah, the militant Shia organisation that controls its neighbour to the north, with which it fought a war in 2006.
Israel, whose intelligence on Syria is probably better than anyone's, at least as good as that coming out of the US, is closely monitoring Syria's chemical weapon stockpiles.
Defence Minister Ehud Barak said this week: "Syria has advanced anti-aircraft missiles, surface-to-surface missiles and elements of chemical weapons. I directed the IDF (Israeli Defence Forces) to prepare for a situation where we will need to consider the possibility of an attack."
The international community has spent much of the past 17 months arguing about what it should do in response to Syria. Suddenly there is great urgency about finding a resolution.
US involvement, through intelligence gathering and diplomatic pressure on Syria's neighbours, took a more direct route recently when the CIA was reported by The New York Times as active along the Turkey-Syria border, making sure weapons flowing into Syria got to the Free Syrian Army and not Al Qa'ida, which is trying to use the conflict to create another Iraq-style failed state that it can use as a new base.
It also appears that US special forces are using Jordan as a base for covert missions to check Syria's chemical weapons stockpiles.
Remarkably, the Free Syria Army is winning this war - the rebels' dramatic, sustained move into Damascus is proof of this.
It is remarkable as they are up against a much stronger opponent. The Syrian army has massive firepower supplied by Russia. It also has Shabiha, the notorious plain-clothes militia that is effective because Syrians can never be sure who they are.
There was only one possible strategy that was ever going to give the FSA a chance of winning this conflict and it has employed it: guerilla war.
When I spent time with the FSA along the Turkey-Syria border in March, one of its commanders was blunt when asked what strategy he was using. "Shoot and hide," he said. "We are snipers - we shoot, we run, we hide."
In the battle for Damascus, the FSA is using the same strategy.
The rebels have been engaging Syrian forces in the centre of the capital, then retreating to safe houses in nearby suburbs. The brutality of the regime's attempt to crush this uprising has pushed people who might otherwise have remained neutral to support the rebels.
There is no reason to think the bloodshed will stop. Bashar al-Assad knows he long ago crossed the line of acceptable behaviour, so he has nothing to lose. This is why the use of chemical weapons is a possibility.
If he begins to use chemical weapons then the West - particularly the US, Britain and France - will have to decide whether to launch a military raid to try to seize those weapons. Syria's neighbours, Turkey, Jordan and Israel, will also want to move quickly.
This would take the conflict into dramatic new territory. How would Russia respond? It has defended Assad and has a massive naval base in Syria.
The most likely answer to what comes next is chaos - there are so many scores to be settled that any smooth transition looks impossible.
The Sunni majority, which has suffered massacres in which their children have had their throats cut and been shot in the head at point-blank range, will want revenge against the Alawite minority who have driven the atrocities.
The two key questions are: how will the regime fall and what will replace it? Syrians themselves are clearly expecting things to get worse - in the past week tens of thousands have flooded into Turkey, Lebanon and Jordan. And if further proof were needed, many are even trying to flee into Iraq. There are not many places on earth that make Iraq look like a good option.
