Last week, Michael Doran of the Brookings Institution and I had an op-ed in the New York Times arguing for a greater level of American involvement in Syria. Among the steps we advocated was putting an initial focus on helping the rebels to take Aleppo, the country’s second-largest city and commercial hub.

Today you can read in the Weekly Standard a first-hand report on how the battle of Aleppo is progressing by Jonathan Spyer, a Jerusalem Post columnist. Spyer, who recently visited the area, confirms the extent to which Assad has lost control of the land between Aleppo and the Turkish border:

I entered Aleppo governorate in broad daylight, crossing through an olive grove on the Turkish border. Once over, I was picked up by a driver affiliated with the Free Syrian Army, and we continued on our peaceful way, taking the highway to the warzone of Aleppo city. The Assad regime no longer exists as a functioning presence in the surrounding countryside. The FSA, in its various local manifestations and with its various political allies, has the final word.

However, Assad retains an ace card—his air force. Spyer goes on to note:

The relative tranquility in the villages between the border and Aleppo city is deceptive, however. Assad’s power is not manifested in the few remaining points on the ground he controls but in his near-complete mastery of the air. This enables the dictator to maintain a reign of terror even over areas physically held by his opponents, as we would discover.

That is why Doran and I argued for the U.S. and its allies to impose a no-fly zone, thus taking away from Assad the major advantage he continues to hold—and without running the risk of providing to the rebels sophisticated anti-aircraft missiles that could fall into the wrong hands. As Spyer notes, the battle of Aleppo is currently a stalemate but the U.S. could break that stalemate easily—and help to bring about Assad’s downfall.