There have been warnings that Russia could use weapons of mass destruction in Ukraine. However, a simple cost-benefit analysis reveals that Russia has nothing to gain from using WMD in Ukraine. There would be no “Japanese effect” as the Ukrainians would not capitulate, rather would this if anything have the opposite effect in further galvanizing Ukrainian public opinion against the Russian aggression. While it is true that the Russian invasion of Ukraine was based upon a miscalcalculation on the part of Moscow, the Russian analysis that Kyiv would fall within days was universally shared by Western military analysts. This case is fundamentally different however, no analyst in his/her/their right mind imagines that Russian use of weapons of mass destruction would prompt a Ukrainian capitulation or even lead to Ukrainian demoralization, on the contrary so. It is important to be cognizant that President Putin always was and remains a coldly calculating cynic and master of realpolitik. Why did Russia invade Ukraine? Russia planned to conquer the entire Europe so as to become a superpower once more in order to become able to defend Siberia against a future Chinese military that will be much larger than at present. Both Russia’s and China’s ambitions are perfectly rational as is their present mutual detente. Western leaders would be particularly well-advised to rely on President Putin acting rationally; and act in a calculated and calibrated manner themselves in optimally supporting Ukraine.