I believe I have the answer.
Only recently Russia sold a new missile defence system to Iran and Syria.

If the U.S. is going to invade Iran, they need to identify the capabilities of this new missile system.
It is easier to strike Syria and build up a picture of what they are facing, this is good military sense. But bad news for the world if it is true.

The U.S. military always softens up it's target with air strikes, I believe around or after Christmas it is going to kick off.

DEBKAfile�??s military experts conclude from the way Damascus described the episode Wednesday, Sept. 6, that the Pantsyr-S1E missiles, purchased from Russia to repel air assailants, failed to down the Israeli jets accused of penetrating northern Syrian airspace from the Mediterranean the night before.
The new Pantsyr missiles therefore leave Syrian and Iranian airspace vulnerable to hostile intrusion.
They think it might have been a trial run for penetrating Irans air defenses. Syria and Iran recently purchased the latest Russian made air defrense system that the
Russians claimed could not be jammed.

I'm wondering if the Russians were aware of the problem.

http://www.debka.com/...le.php?aid=1301

Maybe they are holding back there ace card.
Syria showed military prudence by not exposing their air defence assets to scrutiny.

Even if the target were just an “empty military installation,” as claimed by the Syrian president, he did not explain the biggest enigma of how Israeli warplanes reached it undetected by Syria’s air defenses. His armed forces are still groping in the dark on this question, and are necessarily constrained from entering into military action until the problem is solved.