Administration officials, including Defense Secretary Jim Mattis and Secretary of State Rex Tillerson, have sought to ease the tension, while at the time same time warning North Korea that if it carries out an attack, it will be met with a crushing response. But they also have underscored that it is Trump's prerogative to use whatever rhetoric he believes is appropriate as commander in chief.
"I was not elected. The American people elected the president," Mattis told reporters traveling with him Wednesday to the West Coast. "The rhetoric is up to the president."
The "fire and fury" controversy has renewed questions among critics about whether Trump has the appropriate temperament to control the U.S. nuclear arsenal. It also follows a Defense Intelligence Agency assessment, first reported Tuesday, that North Korea has successfully produced a miniaturized nuclear warhead that can fit inside its missiles.
During his campaign, Trump promised that he would "do everything in my power never to be in a position where we will have to use nuclear power." But he also repeatedly declined to say whether he would use nuclear weapons first in a conflict. On Thursday, he said he would like to "de-nuke the world," but that until other countries get rid of their nuclear weapons, "we will be the most powerful nuclear nation in the world, by far."
A December 2016 assessment by the Congressional Research Service stated that the president "does not need the concurrence of either his military advisors or the U.S. Congress to order the launch of nuclear weapons." Additionally, the assessment said, "neither the military nor Congress can overrule these orders."
The reason is simple: The system is set up for the United States to launch an attack within minutes, so that if the United States is under a nuclear attack, it can respond almost instantly, said Bruce Blair, a former nuclear watch officer. Trump would presumably meet with Mattis, Chief of Staff John Kelly, Chairman of the Joint Chiefs Gen. Joseph Dunford and Army Lt. Gen. H.R. McMaster, the White House national security adviser before launching a preemptive attack, but it would "really be uncharted territory" if they sought to stall or slow down an order from the president, Blair said.
Under the existing War Powers Act of 1973, the president also is not required to seek congressional approval for any military action until 60 days after the start of a war. Two lawmakers, Rep. Ted Liu, D.-Calif., and Sen. Edward Markey, D.-Mass., sought to stop the president from launching a first-strike nuclear attack until Congress declares war with new legislation in January, but the effort hasn't gone anywhere and is unlikely to with Republicans controlling both chambers of Congress.
Jeffrey Lewis, an expert on nuclear matters at the Middlebury Institute of International Studies, said that he has mixed feelings about the legislation proposed, but "it would be better than what we have now." Trump, he said, is a "walking, one-man campaign for ending nuclear deterrence," the long-held U.S. policy in which it maintains a robust nuclear arsenal in order to prevent other countries from launching a nuclear attack.
But Lewis argued it also would be irresponsible to give any president control of nuclear weapons, but then create a system under which they cannot be used. It would be better, Lewis said, to maintain a small number of nuclear weapons to be used only if attacked.
Steven Hayward, a conservative policy scholar, said that if Trump's senior military advisers stood united against carrying out a preemptive nuclear strike, the "real remedy would be resignation." Hypothetically, doing so might trigger impeachment proceedings, Hayward said, but it isn't clear whether it would be quick enough to stop the president from launching an attack.
"It could happen," Hayward said. "It would be pretty dramatic and it would very unclear what would happen, but it could happen. We're really in uncharted waters here."
Bruce Ackerman, a professor of law and political science at Yale University, said that the principle of civilian control of the military also looms large - "even when the civilian in control is as unpredictable and belligerent as President Trump." Latin American nations have modeled their constitutions along American lines, and their experiences suggest that terrible consequences follow when generals defy their presidents, even under compelling circumstances.
"Worse yet, once the principle is violated, it becomes a precedent for future generals to take the law into their own hands," Ackerman said. "We cannot allow this dynamic to take hold here. If Trump's team can't convince him, they should obey the orders of their commander-in-chief."
