He may be taking a page out of Harry Truman’s book. The US did not give the Japanese an early taste of what they were about to receive, so he may be copying.
I believe that the NorKs do not yet have the technology to be anywhere near a fusion bomb unless Putin or the Chicoms are providing the technology. I believe that it is pure bluster on Kimmie Young One’s part. He hasn’t yet seen DJT do much more than the Kenyan fellow, so I believe he thinks he is playing bullsh*& poker. He doesn’t realize how close he is to taking a dirt nap. Is there an equivalent to Fort Marcy Park in Pyongyang?
A “portable” fission weapon (fits in a tunnel, a building, a truck, container, or ship? Certainly.
Fits in an airplane? Likely.
Droppable like a true bomb? No.
(If they really wanted to use a nuke weapon in the near future, they’d deploy it from a ship in a container that was not yet approaching customs - but close enough inshore to damage and destroy the local area, port, and city. To destroy their enemies, they’d need several hundred nukes. To intimidate the world’s news media and liberal politicians, they only need one.
And a second that they claim to have deployed.
But (in my opinion) they cannot yet fit their weapons (one, two, or a dozen) on a missile, launch it, and expect it to blow up near a target. yet. But that is their goal.