North Korea may soon be able to reach the western United States with a nuclear-tipped ballistic missile. As the latest round of its belligerence has intensified, some have begun to consider how the United States might respond should Pyongyang pull the nuclear trigger.

Some have suggested that, when it came down to it, the United States would not mount a nuclear response—even in the case of a North Korean first strike. According to this perspective, the moral decency of citizens in a modern democracy like the United States precludes its leaders from killing hundreds of thousands (if not millions) of innocent North Koreans just because their leaders indiscriminately massacred hundreds of thousands of Americans.

This line of reasoning is dangerous and misguided.

Kim Jong-un—whose recent interactions with Americans have been limited to Dennis Rodman and company—might be foolish enough to believe this argument, and therefore more prone to contemplate attacking the United States. Then again, Kim Jong-un has ample evidence to refute this narrative. Americans may be known for a lot of things, but restraint in using military force and a high tolerance for U.S. casualties are certainly not among them.

Indeed, when faced with choosing atomic weapons or the potential of a million or more U.S. casualties in an invasion of the Japanese mainland, President Harry Truman opted for the former. The massive parades that greeted U.S. soldiers returning home from World War II suggest that Americans’ moral repulsion wasn’t overwhelming. In fact, a poll conducted shortly after the war found that 85 percent of Americans supported Truman’s decision, while just 10 percent opposed it. By 2009, 61 percent of Americans still supported the decision to use atomic weapons to end the war.

Another survey conducted after the war found that 29 percent of Americans actually wished Washington had dropped more atomic bombs on Japan before it had a chance to surrender, compared to the 19 percent of respondents in that poll who said they opposed Truman’s decision. But this overstates the level of opposition, as 14 percent of respondents said that they opposed using the bomb because they believed the U.S. should have publicly tested it first (presumably to give Japanese leaders a chance to avoid the inevitable).

Thus, only 5 percent of Americans surveyed were completely opposed to using atomic weapons against a non-nuclear armed Japan. There appears to have been far more opposition to the decision among Manhattan Project scientists and Truman administration officials than the American public at large.

More recently, in response to the 9/11 terrorist attacks that killed over three thousand individuals on American soil, the United States launched an invasion of Iraq that led to the deaths of over one hundred thousand Iraqis (of course, America was only directlyresponsible for a small percentage of those). And Iraq wasn’t even involved in 9/11.

Although the American public eventually turned against the Iraq War, this had far more to do with the number of Americans dying than the welfare of Iraqis. Americans aren’t particularly callous: all nations are far more sensitive to deaths on their own side than those of their adversaries or even their allies.

One doesn’t need to be a leader of a country that has already been devastated by a U.S. conventional bombardment to understand that the U.S. response to a nuclear attack would be immediate and absolute. But any lingering doubts Kim Jong-un may have on this issue should be put to rest by a new article in the American Political Science Review by Daryl G. Press, Scott Sagan and Benjamin Valentino.

Seeking to measure the extent to which normative beliefs underpin the “nuclear taboo”—the post-World War II tradition in international politics of not using nuclear weapons—the authors polled roughly 750 Americans about whether they would support the United States using nuclear weapons under different scenarios.

The individuals were randomly assigned to different groups. Three of these groups were asked whether they would prefer that U.S. leaders use a preemptive nuclear attack (instead of a conventional one) to eliminate an Al Qaeda lab in Syria that was trying to build nuclear weapons with fissile material smuggled out of Russia.

The first group was told that America had a 90 percent chance of destroying the lab regardless of whether it used nuclear or conventional means to target it. Not surprisingly, only 19 percent of this group said they would prefer using nuclear weapons. Most of the individuals that supported using nuclear weapons said they believed a nuclear response would send a message to other potential terrorist groups pursuing atomic weaponry. On the other hand, around 48 percent of these same individuals said they would support their leaders’ decision to use nuclear weapons if they learned about it after the fact, even though policymakers had judged that conventional weapons would have been equally effective in destroying the nuclear lab.

Moreover, when a second group was told a nuclear attack had a 90 percent chance of destroying the nuclear lab, while a conventional strike had a 70 percent chance of success, 51.2 percent of respondents said they would prefer that the United States go with the nuclear option. This number rose to 68.6 percent for the third group who was told that the nuclear option was twice as likely to eliminate the terrorist lab compared with conventional missiles (90 percent versus 45 percent).

Furthermore, when those who preferred conventional strikes were asked to select one of five reasons for their opposition to using nuclear weapons, concern over civilian casualties ranked dead last in all three groups. By contrast, a large plurality in all three groups said they preferred conventional attacks because they feared using nuclear weapons would set a dangerous precedent. They were presumably concerned that a nuclear attack today would open up the possibility that the United States could someday become the target of a nuclear attack.

But given the public support for certain preemptive nuclear attacks (against terrorist groups merely seeking nuclear weapons), it’s safe to assume that if a DPRK nuclear-tipped missile ever hit the United States or one of its military bases abroad, Americans would demand that their president engulf North Korea in a “sea of fire.” The more Kim Jong-un is certain of this, the more likely the “nuclear taboo” is to hold.

Zachary Keck is assistant editor of The Diplomat. He is on Twitter @ZacharyKeck.