Trump could win back the nuclear codes. Biden should put guardrails on the nuclear arsenal—now.

On January 6, 2021, then-President Donald Trump inspired a mob attack on the US Capitol to try to prevent the peaceful transfer of power to the Biden administration. Not only was this an unprecedented attack on American democracy, but it represented a serious national security threat. Many saw and see this as one of many examples of an unstable President Trump acting in dangerous, irrational ways. And throughout his time in office, Trump—like all presidents in the nuclear age—had the unilateral authority to launch the US nuclear arsenal.

At any moment, Trump could literally have ended the world with a phone call. Congressional approval is not needed, and the secretary of defense cannot stop a presidential order to unleash the US nuclear arsenal. The system is built for speed, not deliberation. The whole process, from presidential order to the launch of one or hundreds of nuclear warheads, would take just minutes.

The danger that Trump would do something catastrophic was so acute that then-House Speaker Nancy Pelosi desperately looked for ways to prevent the “unstable president from … accessing the launch codes and ordering a nuclear strike,” according to a letter Pelosi wrote in January 2021 to House Democrats in the wake of the January 6 attack on the Capitol. Chairman of the Joint Chiefs of Staff Mark Milley was convinced that Trump had suffered “serious mental decline in the aftermath of the election” and took the extraordinary step of ordering his staff to come to him if they received a nuclear strike order from the president. “No matter what you are told, you do the procedure. You do the process. And I’m part of that procedure,” Milley reportedly told the officers. “You never know what a president’s trigger point is.”

Pelosi and Milley had plenty of reasons to worry that Trump could start a nuclear war. In August 2017, in a thinly veiled nuclear threat, Trump warned North Korea that it would be “met with fire and fury and frankly power, the likes of which this world has never seen before.” Trump mocked Kim Jong Un, the North’s leader, writing “I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!” According to then-White House Chief of Staff John Kelly, Trump privately discussed the idea of using a nuclear weapon against North Korea and suggested he could blame a US strike on another country.

Actually, however, Milley was not correct when he told his staff that he was part of the formal procedure to launch nuclear weapons. As former Defense Secretary William J. Perry and I wrote in our 2020 book, The Button, policy established during the Cold War puts decisions about the use of nuclear weapons solely in the hands of the civilian president, not Congress and above all not the military. All the president need do is call the Pentagon’s War Room—using the nuclear “football” or some other means—and identify himself and give the order to launch. The president may choose to consult with senior advisors such as Milley but is not required to.

Milley broke these rules, as others broke them before him. During the Watergate crisis, then-Defense Secretary James Schlesinger was so concerned about President Richard Nixon’s mental state and alcohol consumption that he told military commanders that if Nixon ordered a nuclear strike, they should check with him or Secretary of State Henry Kissinger first. Sen. Alan Cranston phoned Schlesinger, warning him about “the need for keeping a berserk president from plunging us into a holocaust.”

Should Milley, Schlesinger, or any military leader, let a clearly unstable president start a nuclear war just to follow protocol? Of course not. But officials should not have to break the rules to do the right thing. The United States needs to change the policy that put Milley and Schlesinger in an impossible spot.

With just six months left in office, President Biden can fix the system for himself and all future presidents. To do so, Biden should announce the White House will share authority to use nuclear weapons in any first strike with a select group in Congress. The Constitution gives Congress the authority to declare war, not the president. The first use of nuclear weapons is clearly an act of war. In a situation where the United States has already been attacked with nuclear weapons, the president would retain the option to act unilaterally.

President Biden would have to make such a policy change by executive order. Passing congressional legislation would be more durable but is unlikely in the current political environment. If Trump wins the election, he would likely reverse Biden’s order. But if Vice President Kamala Harris wins, the new policy could be strengthened over time with legislation.

Such a policy would provide clear directives for the military to follow: A launch could be ordered only if the United States had already been attacked with nuclear weapons or if Congress had approved the decision, providing a constitutional check to executive power. This would be infinitely safer than our current doctrine.

As an important part of his legacy, President Biden must put guardrails on presidential authority to start nuclear war now before the next dangerous leader gets elected—whomever and whenever that may be. We must never again entrust the fate of the world to just one fallible human. This is not about whose finger should be on the button. This is about making good policy that can keep Americans—and people around the world—alive, regardless of whom US voters happen to put in the White House.