It appears evident that it was the Syrians who took down the Russian Il-20 surveillance plane. Russian MoD claims that Israelis misinformed Russia about the target of their strikes, whose fighters used the hapless Il-20 for cover.
This would make it a combination of Arab incompetence and Jewish mendacity. A most stereotypical combination.
Now Russia has done its part to meet Israel halfway during this conflict:
Some sort of reaction is definitely called for.
That said, delivering the S-300PMU to the Syrians isn’t without its risks. Israel is not going to be very happy about it, and at the end of the day, Israel >> Khmeimim AFB in terms of military power (unless the most enthusiastic fanboys of Russian military hardware are right after all).
Not to mention that Israel has the world’s premier superpower at least half in tow.
It may well even launch a strike on the S-300 before it’s even set up, which would be $1 billion down the drain at best, a few more dead Russians at worst.
So my two major questions at this point are:
1. Who’s paying for this? One certainly hopes Syria (read: Iran).
2. What is Russia going to do if/when Israel attempts to take it out? $1 billion is not entirely negligible – for comparison, it’s the annual cost of Russia’s military operations in Syria, or its aid to the Donbass.
Even if no Russian uniformed personnel are hurt, this would demand a hard reaction to save face. Essentially Russia would need to adopt BDS as state policy. Western journalists will talk of a resurgence of Russian anti-Semitism. Perhaps more Western sanctions.
Anyhow, I do hope the kremlins know what they are doing.