@TiddyTidTwo
"US and UK putting out this chemical warfare stuff is to prepare us. That HAS to be the red line, surely"
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By crossing the red line I presume you then mean NATO imposing a no fly zone., at which point NATO is at war with Russia (some could argue it already is).
NATO is considerably technically superior to the Russian forces and would win. Given that Putin has consistently demonstrated that given a choice between capitulation : humiliation and escalation he will always choose to escalate.
Faced with a superior NATO force his choice is defeat or go tactical nukes. He will go for tactical nukes at which point....
For the sake of the world we need cool heads and avoid drawing any red lines that escalate this situation.