The president of the United States is losing his head, and that means the rest of us must keep ours. At 8:06 a.m. Eastern Daylight Time, Donald Trump posted this on his Truth Social site:A whole civilization will die tonight, never to be brought back again. I don’t want that to happen, but it probably will. However, now that we have Complete and Total Regime Change, where different, smarter, and less radicalized minds prevail, maybe something revolutionarily wonderful can happen, WHO KNOWS? We will find out tonight, one of the most important moments in the long and complex history of the World. 47 years of extortion, corruption, and death, will finally end. God Bless the Great People of Iran!The world, unfortunately, has gotten used to Trump’s overheated rhetoric, and to dismissing the commander in chief as something of a crank who (as the French president recently advised) should perhaps keep more of his thoughts to himself.But the president’s statements are policy, and he has now made it the policy of the government of the United States that at 8 p.m. Washington, D.C., time (3:30 a.m. in Tehran), he will order the U.S. military to destroy Iran and its entire civilization—permanently—unless his terms are met. (He did not specify those terms, but on Easter Sunday, he posted a frenzied and obscenity-laden message to Truth Social demanding that Iran reopen the Strait of Hormuz.) Whether the president is saying this with full control of faculties or has well and truly lost his mind is irrelevant: He is still the president, and so we must consider the meaning of this policy.[Read: Trump threatens to destroy an entire nation]First, Trump is vowing to eradicate a nation of 92 million people and their entire culture, “never to be brought back again.” No leader standing in front of a court at The Hague would be able to finesse that language: “A whole civilization will die tonight, never to be brought back again” doesn’t leave a lot of room for charitable interpretations. Even Richard Nixon, the author of the “madman theory”—the notion that presidents might seek advantage over an enemy by appearing to be irrational—never publicly threatened to wipe out Vietnam. Trump could argue that his threats against bridges and electric plants might not be war crimes, if they have a military use, but his promise to eradicate a civilization from the Earth is a flat threat of genocide.Second, the most important aspect of Trump’s threat is that it implies the use of nuclear weapons. Trump did not explicitly invoke nuclear arms, and he claims to abhor the idea of using them. (He has also, of course, asked why America has them if they can’t be used.) But the United States could launch every conventional munition it has, and although that kind of onslaught would immiserate the people of Iran, result in many deaths, and make reconstruction a long-term nightmare, Iranian civilization would survive. German civilization survived years of bombing so intense that the firestorms melted glass and asphalt; Japanese civilization survived similar incendiary attacks and two nuclear bombs. A threat to destroy an entire civilization in one night, assuming he means it, can only be fulfilled with the wide use of nuclear weapons.The president now sounds no different from the authoritarian rulers of the world’s worst regimes. North Korea, when it was pursuing nuclear arms, would threaten to turn cities into “lakes of fire”; Iran, of course, has often threatened to “wipe Israel from the map,” which is why the world has been trying to stop Iran from getting nuclear weapons. Now Trump is making those same kinds of threats—and he has nuclear weapons.In the past, Trump’s sycophants in the conservative media have tried to wave away his bellicosity as just the way he talks, and dismiss concerns as pearl-clutching from people who just don’t get him. But would any American offer the same grace to Kim Jong Un or the Iranian Supreme Leader Mojtaba Khamanei, if they used the language Trump employed today?Imagine how the United States would react if the leader of a major nuclear-armed power made a similar threat—if Russian President Vladimir Putin said something like Ukraine must submit to my demands by 0800 hours or I will eradicate Ukrainian civilization, or if Chinese President Xi Jinping said, Taiwan must accept Chinese rule by sundown or Taiwan, in one of the most important moments in the long and complex history of the world, will be gone and never return. At the least, the United States would likely go on heightened military alert—and might even raise the readiness of its nuclear forces—because we would have to assume that such statements from a national leader are not mere bluster.Even during the Cold War, American planners avoided such pronouncements. U.S. nuclear strategy prioritized targeting enemy nuclear weapons, command and control, military assets, and the enemy government. There were good reasons for this list of priorities: These targets mirrored what the Soviets would strike in the United States. Had World War III erupted, the net effect would have been something akin to what Trump is threatening now, but as the horrifying consequence of a nuclear exchange, not as an intended goal. (In 1967, Robert McNamara, in a moment of exasperation with some hawkish questioning from Congress, blurted out that if the Kremlin’s leaders attacked America, they knew we’d kill 120 million Soviets; he was trying, however, only to reaffirm the deterrent logic of mutually assured destruction, not advocating for such action.)If Trump did give an order to attack civilian targets that have no military value as a means of collectively punishing the Iranian people, he would be ordering war crimes. If he directs the widespread and irrevocable destruction of Iranian civilization—that is, if he commands a genocide and especially if he approves the release of nuclear weapons—the U.S. military should refuse such blatantly illegal orders.In a better world, Trump would face a revolt in his Cabinet over such orders. Unfortunately, his Cabinet is stocked with needy courtiers who, to date, have preferred to enable the president’s reckless schemes rather than argue with him or resign in protest. Indeed, they were chosen not for the strength of their character but for their pliancy: People such as Pete Hegseth and Tulsi Gabbard only exist as national political figures because they circle Trump like dwarf moons around a gas giant. They are not going to stop him.[Barbara A. Perry: This is not how presidents typically communicate]Only Marco Rubio’s resignation would matter. Rubio, as secretary of state (and concurrently, national security adviser) has a certain amount of political gravitas left, and if he spent it by threatening to walk out of the White House tonight as a private citizen, he might sway Trump away from his mad threats. If Trump wishes to follow through on his threats, and the Cabinet declines to stop him, Congress could in theory convene and attempt to restrain him—but that seems even less likely to happen, despite some panicky concern from a few GOP senators.Should Trump persist in his threatened course of action, then, only a mass resignation of senior officers would stand between the president and a campaign of genocide. By this, I do not mean a mutiny or coup. The answer to Trump’s lawlessness is not more lawlessness. But American officers have a positive duty to refuse illegal orders, and the destruction of an entire civilization with nuclear weapons—which poses no similar threat to the United States—is as illegal as it gets. We must all hope that Trump’s message was an early morning rant that got loose in the wild before anyone could stop him. But it’s out there now, and we are just hours away from his deadline. He is the president and his words have meaning, and he has publicly committed the United States to the extermination of an entire nation.If Trump gives that order, the chairman of the Joint Chiefs of Staff should lay his stars down in front of Trump. Then, each general who gets the order should do likewise, and each man—and it will be men, in Hegseth’s Pentagon—promoted as a replacement should do likewise, until Trump has a pile of stars and eagles on his desk. Trump may eventually find someone to fulfill his orders, but people of honor and duty need not be the unwilling instruments of so great a sin.