In most every uprising that topples a government, there's a pivotal moment when the momentum swings dramatically to the opposition and a regime that once seemed sturdy suddenly appears extremely vulnerable.
That moment may have come with Wednesday's bombing inside the National Security building in Damascus, the most powerful blow the Syrian opposition has yet delivered to President Bashar Assad's regime since the uprising began in March 2011.
The attack hit during a meeting of security chiefs; the dead included two of the country's top security officials: Defense Minister Dawoud Rajha and the Deputy Defense Minister Assef Shawkat, who was married to Assad's sister Bushra.
Between them, Assad and his late father, Hafez Assad, have ruled Syria with an iron fist for more than 40 years and had never suffered such an attack on senior figures in their inner circle.
"This is a situation that is rapidly spinning out of control," U.S. Defense Secretary Leon Panetta said of Syria during a Pentagon news conference.
The attack also shatters the notion that Assad and his government still have firm control of Damascus.
Since the uprising began, most of the fighting has taken place far from the capital, in cities such as Homs and Hama. Damascus, by contrast, had a semblance of normalcy. This allowed the Assad government and its supporters to at least entertain the notion that the security forces might eventually crush the rebellion in the provinces and ultimately keep control.
Even as the uprising has spread across Syria, Assad has maintained the support of key constituencies in the capital: the security forces, the business community and the minority Alawites, which is an offshoot of Shiite Islam to which Assad and many other top leaders belong.
But the fighting has recently crept into the suburbs of Damascus. The past several days have seen the most intense and sustained gunbattles so far in the city. Instead of setting off an occasional bomb, the emboldened rebels have felt strong enough to engage in shootouts in Damascus. And Wednesday's attack showed their ability to penetrate the very core of the country's security system.
It's still far from certain what the full impact will be. While Assad has been weakened, he remains in power and his army has far more men and firepower than the rebels, at least for now.
The rebels have not shown themselves to be a particularly well-organized force. With a few exceptions, they have not been able to take and hold cities or other significant patches of territory. Carrying out attacks in Damascus — even one as devastating as Wednesday's bombing — is a far cry from taking over the city.
Still, the blast is the most devastating of a series of damaging psychological blows to the Assad regime. In recent weeks, several high-profile officials have defected, including the country's ambassador to Iraq and a prominent security official.
The latest violence in Damascus could encourage more senior figures to abandon Assad. Government forces have been defecting steadily as the fighting has dragged on, and at some point, that could turn into a wholesale departure of troops.
Syria's economy is in shambles, and the country is increasingly isolated internationally, with the U.N. considering a resolution that would put more pressure on Syria to comply with a peace plan. The U.S. and other Western nations are calling for Assad to give up power. The Arab world has turned against him. Turkey, an ally before the uprising began, is now one of Assad's harshest critics. Russia and Iran are among the few countries still giving Syria's leader some support.
Having witnessed the fall of other authoritarian rulers in the Arab uprisings, Assad has clamped down with harsh security measures since the Syrian revolt began and has cast the opposition as terrorists. He has shown no signs of compromise and still appears wholly dependent on his security forces to deal with the crisis.
But with Wednesday's bombing, Assad lost key security chiefs who have been central to this policy.