Russia has already provided Iran with S300s and most likely S400s. Russian supplied air defense forced Israel to abort its retaliatory strike stemming from the unchecked Iranian pummeling of Nevatim last October. Whether the Iranian missiles used on Nevatim have the range to hit Diego Garcia is debatable. What is not debatable is the Iranian capability to hit those 54,000 sitting duck American troops at their trip wire bases all around the Persian Gulf.
Durka durka durka. Blah blah blah…