As the threats exchanged between the leaders of the United States and North Korea escalate, President Donald Trump's rhetoric seems to draw from the "madman" playbook employed by President Richard Nixon during the Vietnam War. Trump should not expect the results to be any better, and they might be much worse. American leaders should be extremely wary of the risks of flagrant nuclear brinksmanship.

The paradox of American nuclear power is that the nation’s overwhelming arsenal is almost unusable. The damage created by a single nuclear strike would be so great, it would undermine most American strategic purposes. The public revulsion, even from Washington’s closest allies, would make the United States a global outcast. And American nuclear action would justify others contemplating the same, tearing apart 50 years of global non-proliferation efforts.

These are the circumstances that motivated Chinese leader Mao Zedong to call the United States a “paper tiger” during the Cold War. Mao never took American nuclear threats against his country seriously, as he proved when he attacked US soldiers on the Korean Peninsula, in Indochina, and in other settings. Mao believed that nuclear weapons constrained the United States more than its adversaries. President John F. Kennedy agreed, and began a process of broadening American conventional capabilities (“flexible response”) to create non-nuclear options for combatting aggressors, like Mao.

President Richard Nixon inherited the unwinnable conventional war in Vietnam that Kennedy’s flexible capabilities facilitated. Nixon recognized that military options below the nuclear level enabled self-destructive quagmires, as the country sent thousands of soldiers to fight communists in distant, inhospitable lands. The “Nixon Doctrine” promised to reduce the use of American conventional forces. The president looked for a way to rely more heavily on nuclear weapons, converting their overwhelming firepower into diplomatic and military leverage, without actually irradiating foreign territories.

The destructive power of nuclear weapons remained out of proportion with American political aims, and foreign leaders continued to doubt American will to use them, but Nixon was determined to make his biggest bombs into better bullying tools. As he told Henry Kissinger and other advisers on numerous occasions, he would convince American adversaries that he had strong “guts,” and personal “will in spades” to get tough where predecessors had backed down.

Nixon had to show that the limits on how his predecessors thought about nuclear weapons did not apply to him. He was prepared to think about the unthinkable. He would be less predictable and more experimental. He would act a little “mad,” or at least create uncertainty about whether he still followed the accepted rules of behavior for the leader of the free world.

Among serious strategists, “madmen” are not afraid to fail, or blow up the world and themselves. That is not their preferred outcome, but they are prepared to take massive risks for specific purposes. To be mad is not to be irrational. There is a steely rationality in the willingness to combine extreme force with potential suicide. The madman strategist is ready to press the nuclear button if the adversary doesn’t back down. The adversary will give in, according to the logic, because the potential damage is just too devastating, and he thinks the madman might be serious.

During the Cold War, leading American game theorists modeled this behavior. Noble Prize-winning economist Thomas Schelling called it the “threat that leaves something to chance.” Daniel Ellsberg of Pentagon Papers fame spoke of the “political uses of madness.” Henry Kissinger worked closely with Schelling and Ellsberg during his two decades at Harvard University, and he brought this thinking to the White House.

In the first year of the Nixon administration, Kissinger and the president implemented a madman strategy to scare the Soviets into helping the United States extricate itself victoriously from Vietnam. Nixon hoped to withdraw American soldiers, and simultaneously gain desired concessions from the communists, by encouraging the fear that he would go nuclear. Nixon instructed Kissinger to tell foreign leaders that the president had become unhinged, even obsessed with getting favorable terms in Vietnam.

This was largely true, but Nixon, Kissinger, and every cabinet official in the administration remained unwilling to consider a nuclear strike in Vietnam, or anywhere else.

To be mad is not to be irrational. There is a steely rationality in the willingness to combine extreme force with potential suicide.

The Nixon-Kissinger madman strategy failed because Soviet and North Vietnamese leaders, like Mao Zedong in China, recognized that the United States had much more to lose than gain from turning the Vietnam War into a nuclear conflict. Nixon could make Indochina unlivable, but he could not save the South Vietnamese government, or America’s reputation as a bulwark of freedom, by feigning madness. All the major actors saw through Nixon’s bluff.