This should be a game changer if confirmed: “Turkey activated the radars of its Russian-made S-400 anti-aircraft systems in order to detect US-made Greek F-16 fighter jets” https://www.ekathimerini.com/257682/article/ekathimerini/news/pompeos-visit-prompted-by-turkeys-s-400s

This has always been a serious concern—that Turkey would use the S400 against US or NATO allies. The other concern being that if connected to other NATO systems, the S400 could pose a major interoperability (cyber) threat.

And I am hearing from Greek friends that the Turks may have done just that: connected S400 to NATO radar systems.

If all of this can be confirmed by a US official, a swift response will be necessary. Nothing less than Turkey’s NATO membership should be at stake.