Western Damascus burns - this photo reportedly take at around sunset on Thursday.
See also today's Syria Live Coverage: Insurgents Take More Bases as Damascus Hit by Bombs
Why has the regime cut the internet? For a possible answer, one has to understand the duality of the insurgency.
The insurgency has many dimensions, but --- to oversimplify it --- two are notable. The first is what we see in Deir Ez Zor or Aleppo or Idlib Province --- a semi-functional military apparatus, either coordinated at the brigade level or on a larger scale. These units seek military victories, destroying the regime's resources and capturing bases, equipment, and territory. This element to the Free Syrian Army has been building for many months, and has not lost a battle since September. It has been advancing steadily since June; however, in recent weeks, this force has surged in a series of one-sided victories from Damascus to Aleppo, from al Raqqah to Deir ez Zor, and beyond.
But in Damascus in particular there has been a second dimension: while there is no place for a traditional military to hide, insurgents have been eating away at the Assad regime for months. Despite efforts to put them down, opposition fighters have been able to hit regime targets and then melt away into the civilian population operating very much like insurgents in Iraq or South Vietnam.
This is the imminent threat. While the military wing of the insurgency is creeping forward, slowly encircling the capital, the lurking enemy lies in many neighborhoods across the city and its suburbs. It is this two-pronged threat that has toppled a half dozen bases around Damascus since the beginning of October.
Now the target is the airport: if that is closed, all sense of normalcy will be gone. Over the last several nights, there have been insurgent attempts to take it. Now it appears that the challenge may be serious enough to close the airport --- maybe for good. The news has already shaken the confidence of the international airlines, hesitant to send their people and planes into what looks like a warzone.
Elements of the Syrian opposition military are closing a noose around the cities of Idlib, Deir Ez Zor, and Aleppo. Once these are surrounded, or possibly captured, Al Raqqah and Hassakah in the north, and Hama in the west, will be the new targets. The insurgents are making a play for Daraa, and are attempting to build strength around Damascus while reducing Assad's military advantage.
Many of the bases recently taken by the insurgents, particularly around Damascus, do not look as though they were vigorously defended, indicating that morale is the lowest it has been. As an insurgent advance takes much of his country, Assad could find his closest defenses dissolving in a matter of days, or even hours.
So the Internet has been cut, in the regime's hope that a disconnected insurgency, and activists who cannot access each other or the outside world, will have trouble galvanising their supporters or organizing the final push. If bad news can be hidden away from Assad's own soldiers, defections may not increase as much as they would otherwise.
I don't think it will work. It did not work when Assad cut the internet in Homs, or in Deir Ez Zor, or in Aleppo, or in Idlib Province. The opposition has been planning for this day. More importantly, this is too little, too late.
An imminent fall of the Assad regime is not an inevitability, but it is a distinct possibility.