Proposals had been made to change Russia's nuclear doctrine to allow for attacking any non-nuclear state that had the participation or support of a nuclear state, Putin said.
I think the most likely response from Putin would be to arm the Houthis/Ansarallah with advanced anti ship missiles, along with selling Iran advanced weaponry. Russia has lots of these missiles in storage, Ukraine has no navy that can be targeted with them. If NATO wants to open Pandora's box and give advanced weaponry for long range strikes to a proxy in Ukraine, Russia can absolutely do the same thing in the Middle East.
I think the most likely response from Putin would be to arm the Houthis/Ansarallah with advanced anti ship missiles, along with selling Iran advanced weaponry. Russia has lots of these missiles in storage, Ukraine has no navy that can be targeted with them. If NATO wants to open Pandora's box and give advanced weaponry for long range strikes to a proxy in Ukraine, Russia can absolutely do the same thing in the Middle East.