If that's true, I guess Russia and Putin are going to look very foolish and weak when that happens, as he has promised beyond a shadow of a doubt that he will defend Iran from the USA, no matter what.

When and where did he promise that?

Putin will defend the international law, issue strong worded proclamations, complain about it in public, while rubbing his hand in private thanks to a booming economy caused by oil prices spike.

A war between Iran and USA is to his benefit. He would look stupid to get involved on the side of Iran in it.