Mr Donald Trump's alarming tweet about his desire to "greatly strengthen and expand" the "nuclear capability" of the United States unleashed a frenzy of media efforts to try to divine his actual policy intentions. It forced some of his advisers into tortured claims that Mr Trump didn't say what he actually said, even as others simultaneously insisted that he did meaningfully put other countries on notice that if he deems them to be challenging US supremacy, they will face an arms race.
But perhaps the most worrisome thing about Mr Trump's nuclear tweet is not the intention to break with decades of international disarmament efforts that it may have signalled, though that's frightening enough on its own. Rather, it's that he saw fit to tweet about nuclear weapons at all.
As the US prepares for President Trump to take near-unchecked control of its nuclear machinery, his nuclear tweet is best seen as a window into his temperament. Mr Trump still does not appreciate that every word he utters carries tremendous weight and could have dramatic, untold, far-reaching, unpredictable consequences - something that is especially true in the nuclear arena. Or, perhaps worse, Mr Trump may be entirely indifferent to this fact.
Arms control experts I spoke with suggested that Mr Trump's willingness to tweet about nuclear weapons raises the possibility that he'll do the same as president - and more to the point, the possibility of him doing so amid some species of international crisis or escalation.
Nuclear non-proliferation expert Jeffrey Lewis of the Middlebury Institute of International Studies points out that in peacetime, any belligerent Trump tweet about nuclear weapons might not appear as alarming, simply because "confirmation bias" might lead key actors not to interpret it in its most frightening light at that moment. But amid rising international tensions, that confirmation bias might work in the other direction, he says. "Imagine we're in a crisis - if he recklessly tweets, people could read these things in the worst possible light," Mr Lewis tells me.
"The North Koreans have a plan to use nuclear weapons very early in a conflict. They're not going to wait. If they think we are going, they're going to use nuclear weapons against South Korea and Japan."
Some reports have indicated that President Barack Obama had privately told Mr Trump that one of the greatest national security predicaments he will face as president is North Korea's escalating nuclear potential. But Mr Trump's tweet suggests an inability to appreciate that Twitter is far too blunt an instrument to handle dangerously sensitive, complex international challenges, and indeed could lead to misunderstandings - and potential catastrophe.
As a potential example, Mr Lewis points out that earlier this year, Mr Trump said he would handle the North Korean nuclear threat by getting China to make North Korean leader Kim Jong Un "disappear". Mr Lewis notes that imprecise language in an errant, bellicose Trump tweet - particularly amid rising tensions - could conceivably amount to an "accidental assassination threat".
"Imagine if the North Koreans are looking for any signs that we're about to attack as their signal that they have to go," says Mr Lewis, adding that if Mr Trump "says the wrong thing" and "gives the impression that we're about to act", the North Koreans might "decide not to wait around to find out if that's true or not", and might hit targets throughout South Korea and Japan where US military forces are stationed. In this telling, Mr Lewis notes, it's possible to envision some kind of ambiguous tweet - such as, "we've gotta get rid of this guy" - unleashing untold consequences. Alternatively, Mr Lewis argues, it's possible to envision a rash Trump tweet locking the US into an untenable position by "closing off the President's ability to back down or compromise", rather than preserving manoeuvring room, making peaceful resolution harder.
More broadly, journalist Eric Schlosser has a compelling piece in the New Yorker that documents the history of how technological dysfunction, as well as human imperfection and folly, have at times almost led to nuclear catastrophe. Mr Schlosser argues that Mr Trump's tweet, combined with escalating rhetoric from American politicians towards Mr Vladimir Putin, and the Russian President's own increasingly bellicose nuclear talk, all combine to boost "the danger of miscalculations and mistakes". It should be obvious that Mr Trump's use of Twitter would be unlikely to alleviate that danger.
Twitter "is a tool of provocation and belligerence in the hands of Donald Trump", nuclear policy specialist Bruce Blair of Princeton University tells me, adding that it's easy to envision Mr Trump tweeting a warning to another world leader that "if you do this or that, you'll be sorry". Mr Blair says the worry isn't necessarily that a single Trump tweet might alone unleash nuclear catastrophe, but rather that one could very well exacerbate an already-existing situation in far worse ways than otherwise might have happened, which, when you think about it, isn't a particularly reassuring distinction."Almost any threat could be perceived as warranting some sort of response that's not only rhetorical, but operational," he says. Mr Blair adds that Soviet leader Leonid Brezhnev "in 1973 threatened to intervene in the Arab-Israeli conflict. That triggered the United States under (Richard) Nixon to respond by going on nuclear alert. We went to Defcon 3. Words and threats have consequences in the nuclear operations world, and can instigate a cycle of escalation that spins out of control". All this could be made a lot worse if Mr Trump conducts "nuclear diplomacy by Twitter", Mr Blair says.
And so, whatever Mr Trump's real intentions for the US nuclear arsenal and the future of international disarmament efforts, his willingness to use Twitter to posture and chest-thump around nuclear matters should itself stir urgent concern. This will be particularly true if it holds over into situations involving escalating tensions.
In fact, one thing that Mr Trump and his advisers should be pressed to answer right now is whether he will put his Twitter feed on ice in such situations. Given what we've seen from Mr Trump thus far, there's simply no reason to assume that he will be so inclined.