SEOUL — Donald Trump at times engages in such flights of rhetorical fancy that a lot of people think he’s crazy or unpredictable. How can you be sure of a president who talks about destroying North Korea, who holds out “the military option” — but professes to want to avoid conflict?

There are two schools of thought about the Trumpster. Just about every college professor, like the columnists for the New York Times and Washington Post, thinks he’s unhinged and we’d better watch out, no telling what will happen. Then there are those who believe he’s crazy like a fox, that he may act and talk crazy but deep down he knows what he’s doing.

It may be too early to pronounce judgment on Trump’s sanity. He’s only been in office for months. It’s possible to say he’s on a steep learning curve, a shakedown cruise, any analogy, but here’s an issue that people worry about. That is, does he really have his finger on the nuclear button? Can he flick a switch and send bombers off on a nuclear strike if he’s in the mood? What happens if Kim Jong-un annoys him so much that he loses patience, shrugs and says, “I’m not gonna take it anymore.”

Remember, every U.S. president has to carry the nuclear football wherever he goes. Someone in his entourage, maybe a Secret Service officer, has this suitcase inside of which are the codes and buttons needed to open a nuclear war. Could President Trump late one night, snug in bed in the White House, after enduring a particularly vexing barrage of insults mingled with the direst threats from his opposite number in Pyongyang, mumble, “enough is enough,” pat Melania or whoever, wherever, roll over, reach for the football, tear it open, hit the switch and plunge the world into nuclear war?

Just like that? Might it be that easy?

The question is not as frivolous as it might seem. At the height of the Korean War, before President Harry Truman fired him, Gen. Douglas MacArthur, from his aerie in Tokyo, more than once called for nuking the bad guys as the quickest, safest way to get rid of them. Nor was the nuclear option forgotten during the Vietnam War.

Peter Arnett, the Pulitzer-Prize-winning Associated Press star in Vietnam in those days, recalls for the benefit of us “old hacks” who covered the war a memo from Gen. Earl Wheeler, chairman of the Joint Chiefs of Staff, to President Lyndon Baines Johnson on February 3, 1968. The epic siege of the Marine combat base at Khe Sanh in the northwestern corner of what we then called “South Vietnam” had begun. The base was surrounded by “North Vietnamese” forces firing from jungle-clad ridges.

“The use of tactical nuclear weapons should not be required in the present situation,” Wheeler wrote, citing the authority to use COFRAM, “controlled fragmentation of munitions,” meaning artillery shells that would fragment over enemy troops, detonating bomblets over a wide area.

The general added a qualifier that may strike a chord in Korea by its reference to the DMZ, the supposedly “demilitarized zone” between North and South Vietnam at the 17th Parallel. Unlike the DMZ that has separated North from South Korea since the end of the Korean War, this DMZ in Vietnam was porous. There were no peacekeepers watching over inviolable lines; North Vietnamese crossed at will, assaulting U.S. forces operating out of fire bases south of the fictive line.

Incredibly, the general wrote, “Should the situation in the DMZ area change dramatically, we should be prepared to introduce weapons of greater effectiveness against mass forces.” Indeed, he added ominously, “Under these circumstances I visualize that either tactical nuclear weapons or chemical agents would be active candidates for employment.”

President Johnson didn’t want to hear about it. Asked about “the possible use of N weapons at Khe Sanh,” according to Arnett, LBJ responded, “Don’t ever ask me to have to consider it.”

One wonders if Trump, confronted with bad choices, would consider the nuclear “option.” Should he be trusted with the nuclear football? Or does he enjoy baiting Kim Jong-un in a campaign shrewdly calculated in the end to ease rather than heighten tensions? It would be nice to know the Trumpster is crazy like a fox, not a madman with his finger on the nuclear button, itching for a fight in which millions would die.