Russian and Iranian military and commercial planes arrive daily to offload weapons (some of them advanced air or sea defense systems), ammunition, and personnel. Iran is spending an estimated $500 million a month to keep its ally afloat. ...
So, it's as simple as this: if you take out the runways, Iranian and Russian planes cannot land, nor can Syrian planes take off.
Weiss notes there are two key landing places for the extensive support delivered by Russia and Iran: Damascus International Airport (DIA) — which lies about 12 miles east of the city center — and Mezze airbase, which is controlled by the notorious and elite Fourth Armored Division and located just southwest of the capital.
The map below shows the key military infrastructure in Damascus. The DIA is probably out of range of U.S. cruise missiles, but a strike on the Fourth Armored Division would be significant.
Note that Israeli jets have targeted the DIA as well as the Syrian military's fortress on Mount Qasioun, which serves as the mountain headquarters of the Fourth Division, the command of the government's elite Republican Guard, and the Jamraya military research facility.
Mike Nudelman/Business Insider
And here's the view from Mount Qasioun into the city: