The Possible Action of Russia against a US Military Attack on Iran

It's more than a decade that the shadow of threat of US military attack on Iran is overwhelmed the fragile and turbulent region of the Middle East and the Persian Gulf. Both George W. Bush and Barrack Obama emphasized the military option against Iran as the last step and reaffirmed that "all options are on the table". Considering these threats and the fact that in the current international system there is no such a great power to make a balance and deter the possible US action, how could the deterrent role of Russia be analyzed? Does Russia attach such importance to its relation with Iran so that is ready to prevent the US military attack on Iran? Considering Russian cautious diplomacy, the assumption of the present article is that Russia is not a trustable ally for Iran. The history of Russia's behavior in the past towards its allies and the behavior pattern of Russia towards the sanctions against Iran is clear evidence that Moscow has showed paradoxical behaviors. This article aims to assess the possible reaction of Russia against US military threat against Iran, taking into consideration the Russian practice in recent years.