When nuclear weapons were deployed against a U.S. enemy at the end of World War II for the first and last time, the U.S. public initially mostly supported their use. That changed when the fallout - killing tens of thousands within seconds around the Japanese cities of Hiroshima and Nagasaki - became apparent.
It's a sentiment which has lasted for decades, and if anything only appeared to get stronger - until recently.
When President Barack Obama paid tribute to the people of Hiroshima in May 2016, he urged the international community to "choose a future when Hiroshima and Nagasaki are not considered the dawn of atomic warfare but as the start of our own moral awakening."
At the time, nobody would have predicted a victory of Donald Trump in the U.S. elections the following year, however. During his first year in office, Trump has shattered the cautious and history-burdened way we used to discuss nuclear weapons.
On Tuesday evening, Jan. 2, the president further escalated his war of words with North Korean leader Kim Jong Un, asserting that his "nuclear button" was "much bigger & more powerful" than the North Korean leader's. He went on to threaten that the U.S. arsenal "works." Kim had previously taunted Trump in a New Year's Day speech, saying that his nuclear button was always on his desk.
The president's response a day later was only the latest escalation of rhetoric - last summer, Trump had already warned North Korea of "fire and fury" - and his remarks have made analysts wonder whether Trump is aware of the catastrophic impact an activation of either of those buttons would have.
Observers from the United States and abroad criticized the remarks as "infantile" and ill-advised. "Trump plays with the subject so carelessly and recklessly as if it were some kind of video game," argued Aaron David Miller, a fellow at the Woodrow Wilson International Center who has advised several secretaries of state. "My head's exploding," he wrote on Twitter.
Whereas Trump may be the first U.S. president to engage in such rhetoric, there appears to be some precedent for it. The way Trump discusses nuclear weapons may fall into a pattern researchers have at times observed among military officials in the past, as researchers pointed out on Tuesday. They were referring to a 1985 study by Carol Cohn who at the time analyzed military remarks that compared nuclear war with "an act of boyish mischief." Cohn argued that such remarks were an expression of a "competition for manhood," and "a way of minimizing the seriousness of militarist endeavors, of denying their deadly consequences," concluding that they posed a "tremendous danger" in real life.
That's especially true if you're the president of the United States.
The worry is that Trump's remarks are eliminating the reasoning that may have prevented world leaders from resorting to nuclear weapons attacks ever again since World War II. The most well-known explanation for the reluctance to use them relies on the concept of deterrence which assumes that the repercussions of a nuclear war would be so catastrophic - some scenarios predict a "nuclear winter" which would wipe out the majority of humans - that no leader would want to start such a conflict. For that reason, several nations have committed to not using nuclear weapons first.
To some, Trump's August "fire and fury" remarks indicated that the U.S. commander in chief may be willing to launch an attack against Pyongyang without being attacked first - appearing to mark a reversal of decades-long implicit consensus, even though Trump later soften his stance at the insistence of his advisers.
A second theory for why nuclear weapons have remained ostracized for decades frames the decision to trigger their use as a "moral taboo." In her book "The Nuclear Taboo," researcher Nina Tannenwald writes that U.S. leaders have been dissuaded from their use by moral restraint. Relying on historic analysis, Tannenwald argued that "powerful revulsion associated with nuclear weapons had played a role in inhibiting their use."
Compare that with Trump's references to Kim as "rocket man," or his proclamation last August that his "first order as president was to renovate and modernize our nuclear arsenal."
"It is now far stronger and more powerful than ever before," Trump wrote.
The former chairman of the Joint Chiefs of Staff under President Obama, Adm. Mike Mullen, warned on Sunday that the United States was now "closer to a nuclear war with North Korea" than ever before. Trump is not the only one to be blamed for that, as North Korea's continuing missile tests have put significantly more pressure on the president.
But analysts fear that his response to that pressure may normalize the possible future use of nuclear weapons to a dangerous extent. A Gallup poll last September found that U.S. public support for attacking North Korea was already extraordinary high, considering the likely fallout.
An extensive Stanford study last year similarly found that a majority of U.S. citizens would be in favor of relying on nuclear weapons to attack civilians in a nonnuclear-armed adversary. Sixty percent of Americans would accept the death of 2 million Iranian civilians in such an attack, for instance, if the strike spared the lives of 20,000 U.S. military personnel.
"These findings highlight the limited extent to which the U.S. public has accepted the principles of just war doctrine and suggest that public opinion is unlikely to be a serious constraint on any president contemplating the use of nuclear weapons in the crucible of war," wrote the two researchers, Scott Sagan and Benjamin Valentino.
The social media outrage over Trump's Tuesday remarks may have been fierce, but public acceptance of his threats already appears far more widespread than nuclear disarmament advocates would hope.