If s400 is outstanding as it advertised, then how Turkish airforce entering in syria? I am not counting israelis, they are special cases, they are capable of even drop bomb even on america.
The S-400 is only to protect the Russians. NATO forces are bombing everything else except the Russians, so the S-400 has not seen any action.
As for the S-300, the Israelis are apparently flying low, below the S-300's radar horizon, and firing cruise missiles from long range, out of the coverage of the S-300's short range SAMs. Which is a problem for any radar, which is why you need excellent coverage of long range and short range SAMs. However the Pantsir-S1 seems to have failed though. It's terrible against small targets due to its inability to detect them making it their weak link. A long range system that stares higher up cannot operate effectively without a functioning short range SAM with a low level radar that can watch the horizon. Which is why the IAF will use the SPYDER or MRSAM alongside the S-400. The Russians have introduced the Pantsir-S2, with an AESA radar, and it protects their S-400.
There's also a lot of politics involved. The Russians are preventing the effective use of the SAMs supplied to Syria because the Israelis are attacking the Iranians and the Russians want the Iranians out of Syria. The Iranians in turn are working on a short range SAM which can be used to plug the gap and protect them from Israeli attacks.
Long story short, the S-300 is good but needs other supporting systems to work with it in order to make it effective. And the S-400 is the baap of the S-300 and even today only the operators know the actual capabilities of the S-400. We will combine our S-400 with the IAF's SPYDER, Akash (1) and MRSAM (2) at their bases, alongside the IA's QRSAM, Akash (3) and MRSAM (4) which will be forward deployed. Plus we will use aerostats (5) and AWACS (6) that can watch the horizon. And then we have a lot of fighter jets (7) that can quickly punish any attempt made towards the life of the S-400. While at the same time, the S-400, with its 400Km missile (8), will be able to stop any force multiplier from coming close to it. All of this in large number. Of the 8 capabilities I've named, the Syrians do not have even one.
A&N need special attention, chinese will start creating problem in nearby future. When i was a kid, one report came in regional newspaper that chinese has marked A&N as a part of china in their maps.
The S-400 is not enough for A&N. It needs BMD Phase II.