The US and Israeli militaries recently sent a secret delegation to Ukraine to test the capabilities of the Russian-made S-300 air defense systems. Ukrainian military officials explained the limitations of the systems.
The sudden interest in the S-300 is because Russia has, in recent weeks, given the Syrian government enough of the advanced systems to cover their entire airspace. This was done after Israeli attacks along the coast led to the shoot-down of a Russian surveillance plane.
For Israel in particular, the S-300 is seen as threatening to curb their ability to attack Syria with impunity, despite Netanyahu government claims that they’ll keep attacking. Since the deliveries there have been no reports of Israeli warplanes violating Syrian airspace, whereas this was happening multiple times weekly before the deliveries.
Ukraine has S-300s as a throwback to its previously close ties with Russia. Though most of the nation’s systems have fallen into disrepair, their military’s experience with them means they may have some insight in ways to counter the system.
This may be easier said than done, however, as the S-300 has a massive amount of range, and even if not foolproof, any aggressive action against the Syrian systems would likely lead to both a Russian reaction and a serious risk of aircraft being destroyed in the fight.