Israel?
There is absolutely no justification for Russia to transfer SA 300’s to Syria — none. There are exceedingly few actors around Syria with air capabilities sophisticated enough to warrant an SA 300 defense system.
What is likely going on in reality is that Russia is transferring this sophisticated defensive system for the expressed purposes of protecting Iranian assets. As I’m certain you know, Israel recently destroyed a strategic Iranian drone factory and killed a dozen or so highly skilled technicians and military personnel. This action on the part of Israel followed the incursion of an Iranian drone into Israeli airspace. The drone, a replica of the US drone lost a couple of years ago, was crudely armed with explosives and was meant as a terrorize Israel.
Iran was furious and yet Israel told Iran they will continue to destroy such Iranian assets on Syria, which is designed to menace and directly threaten Israel.
Israel has long and loudly said they will not accept such Iranian interference at their doorstep. The transfer of the SA 300 system to Assad is actually for Iran’s benefit.
“There is absolutely no justification for Russia to transfer SA 300’s to Syria — none. There are exceedingly few actors around Syria with air capabilities sophisticated enough to warrant an SA 300 defense system.”
Of course there is a reason. Israeli and Nato/US forces are constantly attacking the Syrian government side in support of the rebels. If you fly CAS for the jihadis, it’s childish to expect your victim not to try to defend themselves.