What Does Russia Gain from the S-300 Sale?

Russia’s surprise announcement it was reinstating its sale of S-300 missiles to Iran caught many observers off guard. It was not clear what the primary motivation was for the Russians in reinstating a sale that the United States and Israel had lobbied so hard against several years ago, so soon after the negotiated framework agreement with Iran. Was it to humiliate President Barack Obama? Was it to reassert Russian influence in the world? Was it to destabilize the talks entirely? (READ MORE)