Just to give you a hypothetical, we would respond by leading a NATO, a collective effort that would take out every Russian conventional force that we can see and identify on the battlefield in Ukraine and also in Crimea and every ship in the Black Sea," said Petraeus.
When asked whether the use of nuclear weapons by Russia would bring the US and its allies into the war, Petraeus said it would, though was cagey about whether nuclear radiation from an attack spreading to NATO states could be considered an attack on them, triggering NATO's Article 5, which obliges member states to defend each other.
"Perhaps you can make that case," he said. "The other case is that this is so horrific that there has to be a response — it cannot go unanswered."
I don't see either side backing down. Are we heading towards WW3?