"Violence has always been implied by previous US presidents: That is to say, if North Korea launched an attack, or crossed certain red lines, they would be met by devastating force. And this has been said even by people in the Obama administration very recently. But the kind of rhetoric that Trump is using is different, and I think probably not helpful, because it just provokes the North Koreans to ratchet up their rhetoric as well. At this point, it seems that we urgently need calmer heads on both sides, and we're not getting that."