With U.S.-North Korea tensions heightened after weeks of fiery and furious rhetoric from President Trump and Kim Jong-un—pushing the world closer to nuclear conflict than it has been in decades—it’s worth taking a breath to consider what forces have kept the world’s nuclear-armed states from irradiating and annihilating each other in a shower of bombs.
Some explanations of nuclear non-use say that nuclear weapons have become, counterintuitively, a stabilizing force on the international system. Once the U.S. and Soviet Union both developed second-strike capability—the ability to respond to a nuclear strike with one of your own—deploying nuclear weapons in the first place became rather unattractive.
Another school of thought points to norms: after 1945, there gradually emerged a strong international understanding effectively prohibiting the first use of nuclear weapons. Both foreign policy elites and the citizens they represent have internalized (and to a lesser degree institutionalized) the belief that nuclear weapons—by virtue of their sheer destructive power—shall not be used except in response to other nuclear attacks. The American public’s support for the two nuclear strikes on Hiroshima and Nagasaki has halved since autumn 1945, when multiple surveys showed over 90 percent American support for some iteration of atom-bombing Japan. Elite military commanders have shown similar reservations. In 2015, James Mattis, now the secretary of defense, told the Senate Armed Services Committee that “fundamental questions must be asked and answered” about the nuclear stockpile, including the possibility of removing land-based nuclear missiles. “Do they serve solely to deter nuclear war? If so we should say so,” he said. The divide between atomic weapons and everything else in the arsenal has kept our nukes grounded, the argument goes. As Nina Tannenwald, a Brown University political scientist and author of The Nuclear Taboo told me, “the single most important restraint we have now on nuclear weapons is the fact that we think of them as different from conventional weapons.”
But a paper published last month in the journal International Security generated some seriously startling data suggesting that, when prompted in certain fairly realistic ways, Americans do not consider the first use of nuclear weapons a taboo, have weak commitments to not killing civilians, and find frightening retroactive justifications for both.
In their study, Scott Sagan and Benjamin Valentino, professors at Stanford and Dartmouth, respectively, ran experiments to gauge Americans’ sentiments towards nuclear strikes on Iran. They gave three nationally representative groups of American adults mock Associated Press articles outlining scenarios roughly parallel to America’s bombing Japan in the 1940s. In the articles, Iran has just violated the Iran Nuclear Deal, and in response to U.S. sanctions, the Iranian Air Force has attacked an American aircraft carrier, killing (unbeknownst to the readers), the same number of Americans as the 1941 Japanese attack on Pearl Harbor. Congress unanimously declares war, the Iranians refuse immediate, unconditional surrender, and the president orders a ground invasion to topple the regime. At the time of the articles, 10,000 American troops have died.
The survey respondents then learn that the Joint Chiefs of Staff have presented the president with two options. Option 1 continues the ground campaign to capture Tehran. In Option 2, America would conduct a “shock strike” on Mashad, Iran’s second largest city, to prompt unconditional surrender by the regime. Option 1, the ground war, remained constant for the three groups. Option 2, the airstrike, varied in the number of Iranian civilian deaths (100,000 or 2 million) and the type of airstrike conducted (nuclear or conventional). Those groups are laid out below:
The groups were asked (1) whether they would prefer the ground war or the airstrike, and (2) if the U.S. decided to proceed with the airstrike, “how much would you approve or disapprove of the situation?”
Here, the findings get grim.
For Groups 1 and 3, in which 100,000 civilians are killed, majorities of the respondents preferred the airstrike on a civilian target to a ground war, and when asked if they would “approve” of a nuclear strike if the president chose it, about 60 percent in each case said they would. In Group 2, almost half of respondents preferred, and 59 percent said they would retroactively approve of, a nuclear strike killing 2 million civilians if it saved 20,000 U.S. troops.
“We were not at all surprised that Americans valued U.S. troops over civilians in another country,” Sagan told me. “But the scope of that preference, that is, the degree to which people were willing to sacrifice civilians in Iran, that to me was very disturbing. That’s a 1-to-100 ratio.”
If inter-state hostility or rogue-state status alone accounted for the American public’s willingness to dispense with its qualms on nuclear use, then nuking Pyongyang might start to look like a politically palatable move. A 2015 Pew survey found that 76 percent of Americans listed their attitudes toward Iran as very or somewhat unfavorable. This year’s Pew survey found an almost identical number, 78 percent, viewed North Korea unfavorably, and a greater share of Americans view North Korea “very unfavorably” than did Iran in spring 2015 (61 percent versus 48 percent).
Sagan emphasized though that the North Korean case has far steeper trade-offs and some additional considerations compared to the ones his experiments tested. “I would not try to interpret our findings to be applicable directly to that case,” he said. North Korea, unlike Iran, has nuclear weapons, and could at least retaliate against our allies in South Korea and Japan and the 28-30,000 American troops stationed in the region, if not against the American continent. And because an American nuclear strike of the kind Sagan and Valentino poll-tested would violate all sorts of international laws and compacts, it seems likely that foreign policy elites would speak out against nuclear use as soon as such an idea were seriously floated. (In Sagan’s experiments, the fictional Joint Chiefs of Staff did not weigh in.)
But the paper brings into striking relief the potential weakness of public opinion as a constraint on using atomic weapons and obliterating civilian targets. Majorities of majorities of Americans were willing to launch a nuclear strike on a city and then blame those on the receiving end. 84 percent of those supporting the strike thought Iran’s leaders were morally responsible for the civilian deaths it caused, because Iran started the hypothetical war. Almost 70 percent of the same respondents further agreed with the statement that because the Iranian civilians did not overthrow the regime, they shared some responsibility for those killed in the strike. “One of the most surprising things was how easily and somewhat creatively people were willing to assign responsibility onto the Iranian people for our attack on them,” Sagan said.
In the abstract, American support for nuclear weapons remains low. “Since the mid-1950s, when you ask, ‘would you be willing to use nuclear weapons first,’ you never have a majority for that,” Nina Tannenwald said. Indeed, a YouGov/HuffPost poll last summer found 50 percent of Americans said the U.S. should only use nuclear weapons as a response to other nuclear attacks, while another 17 percent said America should never use them at all.
She nevertheless called the findings “disturbing,” and said they show how quickly Americans’ nuclear aversions can erode. The only physical constraint on an American president inflicting another Hiroshima is his ability to dial up a set of codes he keeps with him at all times. And the strongest domestic constraints might not be the protests of a war-weary, conscientious public, but the strategic rationality and moral reservations of military brass.
“When you push people in a crisis,” Tannenwald said, “then they seem quite willing.”