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.
To read the full story