When news broke a couple of years ago that Russia was selling S-300 air defense systems to Azerbaijan, the immediate assumption was that this had to do with Armenia. The sale suggested a huge shift in Russia's military policy toward the south Caucasus: Russia has a big military base in Armenia and provides Yerevan with weaponry. So why would it be arming the other side? There were all sorts of theories: it was done to intimidate Armenia into signing a long extension of the base agreement with Russia, or that it was pure mercenary motives. Some noted that the range of the S-300s was enough to cover Nagorno Karabakh (over which a war will presumably be fought) but not Gyumri, Armenia, where the Russian base is.
But what if we were all looking in the wrong direction for the threat, to the west rather than to the south? That's what analyst Anar Valiyev today told The Bug Pit in Baku. He says the S-300 is in fact one of the weapons that Baku has been buying to protect against an Iranian attack. He argues that a war over Karabakh would be fought only on the territory of Karabakh, that Armenia (under pressure from Russia) would not to expand the war into Azerbaijan proper, like an attack on Baku's oil and gas installations (which the S-300s are protecting). Therefore, there's no need to protect Baku from an Armenian attack. So, by process of elimination, it's Iran.
This makes a lot more sense today, as Iranian-Azerbaijani tensions are on the rise, than it would have two years ago. So Valiyev says that the S-300s should be grouped along with the anti-ship missiles and air defense systems it just bought from Israel, that are directed more to the Iranian threat than to a potential war over Karabakh. This is just a theory, but it would explain a lot, like how this squares with a Kremlin policy favoring Armenia and how Armenia's government downplayed the news. Of course, any information in the public about this is likely to be the result of psy ops on top of info ops on top of more psy ops, so who knows. But it's a plausible theory worth keeping in mind.
This reporting was made possible by a grant from the Pulitzer Center on Crisis Reporting