Russia's S-400 Air Defense System

The Russians have definitely made a breakthrough with sales of weapons to some NATO countries with uncertain futures in the bloc (e.g. Greece, Turkey) and strong US client countries such as Saudi Arabia and other Gulf states such as the UAE. One immediate new example: Russia says the UAE is just months away from buying the formidable Su-35 multirole fighter jet, the current Queen of the Russian Air Force fighter fleet.The Russian breakthrough makes sense in technological terms. The US does not have a true competitor to the S-400 system and the US is not anxious to see such systems proliferate. Too bad and too late.