(CNN) During his brief trip to Singapore for a historic summit with North Korean dictator Kim Jong Un, President Donald Trump was introduced to North Korean Gen. No Kwang Chol. Trump extended his hand. Chol saluted. Trump saluted back. Then the two men shook hands.

Trump's decision to salute a high-ranking general in an authoritarian country with a long history of human rights abuses has created something of a stir. The salute is, according to military protocol, a sign of respect and mutual admiration. For the President of the United States to send that signal to a North Korean general struck many people as odd at best, and insulting at worst, to the tens of thousands of North Koreans who have struggled under Kim's dictatorship.

During Thursday's White House press briefing, press secretary Sarah Sanders said Trump was just using "common courtesy."

"It's a common courtesy when a military official from another government salutes, that you return that," Sanders told CNN's Jim Acosta

I'll leave that debate to others. What I am most interested is why Trump saluted at all. And I can think of two broad theories to answer that question.

1) Trump didn't really know what he was doing.

Trump made very clear in the run-up to the Singapore summit that he wasn't doing much in the way of preparation because, well, he didn't think he needed to.

"I think I'm very well-prepared," Trump told reporters during a photo-op with Japanese Prime Minister Shinzo Abe before heading to Singapore. "I don't think I have to prepare very much. It's about attitude."

Now. The White House told CNN Thursday that Trump had been briefed on the various protocols to remember in dealing with Kim and the other North Koreans. And he did avoid donning a big smile when he first met and shook hands with Kim.

But simply because someone told Trump -- or told someone to tell Trump -- what saluting any North Korean military member might mean doesn't mean that Trump listened or remembered (or cared).

What we know about Trump is that he admires the military . He stockpiled his Cabinet with generals and took to referring to them as "my generals." He loves the toughness and discipline of the military. And that admiration isn't just reserved for American troops. Remember Trump's awe at the Bastille Day parade he witnessed alongside French president Emmanuel Macron.

It's uniquely possible that Trump saw a military man saluting him and responded, out of habit, in kind. And that he neither thought about it before it happened or after it was over.

2) Trump knew exactly what he was doing.

There's little question that Trump went into the summit with Kim thinking that you catch more flies with honey than with vinegar.

He had gone the vinegar route months before, describing Kim as "Little Rocket Man" on Twitter and reminding the North Korean dictator who had the bigger nuclear button. Heck, Trump had even called off the summit briefly when North Korea attacked Vice President Mike Pence as a know-nothing.

It was clear in the final days before the summit, however, that Trump was in flattery mode. He expressed optimism that the summit would work out and that he and Kim would get along well.

When Trump strode out to shake Kim's hand, he did so warmly, putting his left hand on Kim's elbow in a welcoming gesture. From that point until the moment Trump left Singapore, everything he did and said was designed to make clear that he respected Kim and wanted to get a denuclearization deal done.

Trump was, in his own unique way, showing that he was willing to meet Kim more than halfway to make this work. And that he understood and respected Kim's views and how he has run his country. ( Trump's willingness to brush aside Kim's record on human rights is, um, troubling.)

Saluting a North Korean general who saluted him is totally in keeping with sending a message of respect to Kim -- and keeping alive, in Trump's mind, the possibility of a deal.

Which is it? Did Trump blunder into a quasi-international incident? Or did he purposely salute as a part of a broader strategy aimed at putting the North Koreans in the best possible mindset to make a deal?

As always with Trump's motivations, it's anybody's guess.