In the military, returning a salute from a military officer of a friendly foreign nation is common practice for US military officers and considered a display of military professionalism. There is no rule that a US president is obliged to return a salute, which is considered a sign of mutual respect.
After Trump and North Korean leader Kim Jong Un walked down a colonnade to shake hands, the pair entered into a room filled with various members of Kim's delegation, the video from North Korean broadcaster KCTV news shows.
Trump starts to shake hands with those in the room. Upon encountering North Korean Gen. No Kwang Chol, who was in full uniform, Trump first extends his hand, to which the general responds with a salute. Trump then salutes back, extends his hand again and the two men shake hands.
A US official told CNN that Trump was briefed on protocol, which is to not salute military officers from other countries. The White House, however, is not viewing Trump saluting a North Korean general as a mistake. It is being seen as all part of the broader goal that day, which was to show respect to Kim and his entourage, according to the official.
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 during Thursday's White House press briefing.
CNN has reached out to the National Security Council for comment.
Retired Rear Adm. John Kirby, a military and diplomatic analyst for CNN, called the moment "striking."
"They can see a propaganda value here and this is basically them showing the level of deference and respect that Trump has paid to them and to their military leaders," Kirby told CNN's Poppy Harlow on "CNN Newsroom." "It was an inappropriate for him to do from a protocol perspective, but now he's played right into the North's propaganda about their legitimacy on the world stage."
Kirby said the appropriate thing for Trump to do in that situation would have been to nod his head and shake the general's hand.
"(Trump's) the commander in chief. He doesn't even salute his own generals. They salute him. That's the way it works. You don't certainly don't do it with leaders of foreign military and you most certainly don't do it with the leaders of foreign militaries of an adversary nation."
CNN's Jeff Zeleny, Noah Gray, Jennifer Deaton, Barbara Starr and Ryan Browne contributed to this report.