You will know there are S-300s in Syria when Israel
blows them up, although there might be a missing
freighter in the Med at some point.
Agreed. The S-300 will have little capability against Israeli fighters penetrating Syrian airspace at low altitude. And Syrian fighters won’t engage — the last air war with the Israelis (over Lebanon and Syria) found the score at Israel: 82 Syria: 0 (Not exact, but in the ballpark; Syria definitely had 0).