On The Rachel Maddow Show Monday night, Cirincione said he thinks the 10 percent figure underestimates the odds. If a conventional war erupted, he said, crossing the line from conventional to nuclear would not be easy to stop. There would be no “firebreak” between the two. Without citing anyone specifically, he said that diplomats are “freaking out” over the way things are going.

Even if neither side had any intent to use nukes, miscommunication or misinterpretation could lead to such use anyway. Especially if a conventional war was already underway.

The potential for escalation would be tremendous because conventional war could exact a horrific toll all on its own. Citing the analysis of chief of the Joint Chiefs of Staff Gen. Joe Dunford, Rob Givens—himself a retired Air Force brigadier general with years of service in South Korea—wrote three weeks ago that the Pentagon has calculated it would inflict 20,000 casualties against North Korea every day that combat in a conventional war continued. It also calculated in simulated war scenarios that the North would inflict 20,000 casualties a day just in Seoul alone.

Under the circumstances, one could expect that more and more top people in both governments would counsel escalation as those tens of thousands of bodies stacked up day after day—even though for the North launching a nuke would be national suicide.

No nuclear bomb has been exploded in anger since the United States flattened half of Nagasaki more than 72 years ago. The Cuban missile crisis was 55 years ago next month. The last atmospheric nuclear test was 37 years ago. But we’ve reached a point where the U,S. pr*sident is saying the U.S. will wipe out North Korea if its government makes an aggressive move, and the North Korean foreign minister is warning that Trump’s comments amount to a declaration of war, that Pyongyang may test a hydrogen bomb over the Pacific, and that it may shoot down U.S. bombers even if they aren’t in North Korea’s airspace.

If the North actually did that, keeping the escalation dominoes from falling would require remarkable self-restraint on the part of the man now in the Oval Office. As we all have seen, he has approximately zero self-restraint. There would be far more than a 50-50 chance of retaliation. And then counter-retaliation. If it begins, nobody can say where it will end. But it’s easy to imagine.

At The Bulletin of the Atomic Scientists, John Mecklin writes:

If North Korea were to detonate a 150-kiloton nuclear warhead (the approximate size of the device it most recently tested underground) in Seoul, about 417,000 people would die and 1.89 million would be injured, according to the Nukemap simulator created by Stevens Institute of Technology professor Alex Wellerstein. Those figures ignore the effects of radioactive fallout.

One bomb, one city.

That would of course not be the end of it.

Skeptics may think diplomatic efforts to rein in this 10 percent prospect are pffffffft before they start, especially given the apparent inability of leaders of both sides to stop taunting each other. But what other choice than diplomacy is there? As National Security Adviser Lt. Gen. H. R. McMaster and dozens of other military leaders have conceded, there is no acceptable military solution to this situation. Unfortunately, that doesn’t mean no military action will be undertaken if tongues aren’t quelled and tensions aren’t chilled.

The U.N. Security Council should be meeting around the clock to ensure that Nagasaki remains the last city to have a nuke dropped on it. Activists should be urging every member of Congress to find ways to edge Trump back from the precipice and figure out the best formula to spur China to do the same with Kim.

The reality is, that like India, Pakistan, and Israel, North Korea is now a nuclear power. There’s no more chance of getting it to give up its nukes than getting those three nations, or France, China, the U.K., Russia, or the United States to give up their nuclear arsenals. The best that can be hoped from diplomacy in the short run is that neither Pyongyang or Washington will launch the world’s first war between nuclear powers. Because the first nuclear war has every potential of being the last war of any kind fought ever, period, because nobody would be alive to fight it.