On several occasions and in varied venues during the past several months, Republican presidential nominee Donald Trump has touted the coercive efficacy of “unpredictability” in defeating foreign adversaries. Interviewed on March 23, 2016 on Bloomberg's “With All Due Respect,” for example, he said this about the potential use of nuclear weapons in dealing with Islamic terrorists: “I'm never going to rule anything out—I wouldn't want to say. Even if I wasn't, I wouldn't want to tell you that because at a minimum, I want them to think maybe we would use them. We need unpredictability,” Trump continued. “We don't know who these people are. The fact is, we need unpredictability and when you ask a question like that, it's a very sad thing to have to answer it because the enemy is watching and I have a very good chance of winning and I frankly don't want the enemy to know how I'm thinking. But with that being said, I don't rule out anything.”

In his initial formal foreign policy speech on April 27, 2016, he declared: “And then there’s ISIS. I have a simple message for them. Their days are numbered. I won’t tell them where and I won’t tell them how. We must, we must as a nation be more unpredictable. We are totally predictable. We tell everything. We’re sending troops. We tell them. We’re sending something else. We have a news conference. We have to be unpredictable. And we have to be unpredictable starting now. But they’re going to be gone. ISIS will be gone if I’m elected president. And they’ll be gone quickly. They will be gone very, very quickly.” (Never mind that Osama Bin Laden wasn't told the Seals were coming.)

A few minutes later, and somewhat contradictorily, Trump said: “Our goal is peace and prosperity, not war and destruction. The best way to achieve those goals is through a disciplined, deliberate, and consistent foreign policy. With President Obama and Secretary Clinton we’ve had the exact opposite—a reckless, rudderless, and aimless foreign policy, one that has blazed the path of destruction in its wake.” In other words, his unpredictability will work; their alleged unpredictability hasn't. On other occasions Trump has said that “I’d be the last one to use the nuclear weapons, because that’s sort of like the end of the ball game." But “I would never take any of my cards off the table."

Trump reprised his theme of unpredictability about 20 minutes into the first presidential TV debate on Monday, September 26 when criticizing Hillary Clinton for having explained her plan for defeating ISIS: “And look at her website. You know what? . . . She's telling us how to fight ISIS. Just go to her website. She tells you how to fight ISIS on her website. I don't think General Douglas MacArthur would like that too much.” He repeated this criticism with similar words toward the end of the debate. Pressed by interlocutor Lester Holt on a different but related matter at another moment in the debate, the issue of nuclear first-use, Trump expressed his opposition: “I would certainly not do first strike.” But in this case, he was talking about the use of nuclear weapons against other nuclear states: Russia and China.

Trump’s somewhat incoherent notions about nuclear unpredictability resemble Richard Nixon’s madman theory: the principle that he or any other leader could succeed in coercing an international adversary by threatening to unleash extraordinary force, including nuclear force, especially if he or she were perceived to be unpredictable, erratic, or crazy. In turn, the madman theory was Nixon’s version of the brinkmanship of President Dwight D. Eisenhower and his secretary of state, John Foster Dulles. (In his 1961 book, The Necessity for Choice, Henry Kissinger observed that brinkmanship was based on the “uncertainty effect”; that is, keeping an adversary guessing about the kind of action the United States might take in any particular case, while implying that the US leaders would go to the brink of using nuclear weapons. Initially a critic of this stratagem, Kissinger later bought into the madman theory when serving as Nixon’s national security adviser.)

Nuclear unpredictability and threat making have not proven themselves to be viable or successful ploys in international relations. The veiled warnings President Harry S. Truman delivered to the Japanese and the Soviets about his “terrible new weapon” did not move either to capitulate. Indeed, such warnings—as well as the actual use of atomic weapons against Hiroshima and Nagasaki—spurred the Soviet Union to build up their own nuclear arsenal. As William Burr and I have documented in our book, Nixon's Nuclear Specter, Truman's and Eisenhower's warnings to Beijing about the possibility of US nuclear use failed to move the Chinese in the direction both presidents wanted them to go. This was also the case in the Dien Bien Phu crisis during the French War in Indochina and the two confrontations between the United States and China during the Taiwan Strait crises of the mid 1950s. 

The impotence of nuclear warnings by the US and the USSR during subsequent decades in Asia, Europe, and the Mideast—whether delivered verbally or signaled by nuclear alerts and shows-of-force—also failed to intimidate or produce positive outcomes. Moreover, in those cases in which nuclear use was considered and explored (for example, during the Dien Bien Phu crisis and the subsequent American war in Vietnam), experts argued that such weapons were not likely to be cost-effective in terms of military results and international and domestic reactions to their use.

Nuclear threat making—which is what Trump means by nuclear “unpredictability”—is unlikely to succeed when the side threatened possesses its own nuclear weapons, or when a non-nuclear state is under the protection of a nuclear state, or when the threat is disproportionate because it is aimed at a small country (or terror organization) and is therefore likely to lack credibility. It is also impossible to threaten nuclear destruction secretly, which means that a President Trump would have to face not only internal opposition to nuclear use from the national security bureaucracy but also from Congress, allied governments, and the domestic and international citizenry. Thus, threats would lack credibility while simultaneously heighten international tensions, promote nuclear proliferation, and run the risk of accidental nuclear use. Trump's “unpredictability theory” thus presents an existential danger to the United States and the rest of the globe.

Along with climate change, overpopulation, and global economic depression, the risks of nuclear proliferation and nuclear-weapons use are at the top of the list of potential catastrophic dangers facing the human race. Whether or not Trump knows anything substantive about the nuclear issue, his stated ideas are simplistic, ill-informed, convoluted, and dangerous. Yes, it is true that US policy has been and still is one in which the use of nuclear weapons has not been taken off the table in certain circumstances, but it is not official US policy to be deliberately unpredictable concerning the use of such weapons.

In Trump’s case, there is an added problem. With Eisenhower, Dulles, Nixon, and Kissinger, true madness—that is, mental illness—was not a factor. They were posing as unpredictable madmen ready to go to the brink. Yes, of course, some of their strategic ideas were dangerous, and Nixon did have some serious personality quirks, but to the best of historians' knowledge, none of these men were certifiably crazy or suffering from a recognizable mental disorder (although Nixon may have come close), and all of them were knowledgeable about strategy, foreign policy, and diplomacy.

What about Donald Trump? He lacks foreign policy experience and knowledge—except for an ability to market his brand name. Off the record, moreover, psychologists consider him to be a narcissist—and possibly one who suffers from a genuine narcissistic personality disorder accompanied by a lifelong history of bullying. Is that a danger? Let's hope we don't find out. He could dangerously redefine the meaning of the “bully pulpit.”